ffmpeg-codecs(1) ffmpeg-codecs(1)
NAME
ffmpeg-codecs - FFmpeg codecs
DESCRIPTION
This document describes the codecs (decoders and encoders) provided by
the libavcodec library.
CODEC OPTIONS
libavcodec provides some generic global options, which can be set on
all the encoders and decoders. In addition each codec may support so-
called private options, which are specific for a given codec.
Sometimes, a global option may only affect a specific kind of codec,
and may be nonsensical or ignored by another, so you need to be aware
of the meaning of the specified options. Also some options are meant
only for decoding or encoding.
Options may be set by specifying -option value in the FFmpeg tools, or
by setting the value explicitly in the "AVCodecContext" options or
using the libavutil/opt.h API for programmatic use.
The list of supported options follow:
b integer (encoding,audio,video)
Set bitrate in bits/s. Default value is 200K.
ab integer (encoding,audio)
Set audio bitrate (in bits/s). Default value is 128K.
bt integer (encoding,video)
Set video bitrate tolerance (in bits/s). In 1-pass mode, bitrate
tolerance specifies how far ratecontrol is willing to deviate from
the target average bitrate value. This is not related to min/max
bitrate. Lowering tolerance too much has an adverse effect on
quality.
flags flags (decoding/encoding,audio,video,subtitles)
Set generic flags.
Possible values:
mv4 Use four motion vector by macroblock (mpeg4).
qpel
Use 1/4 pel motion compensation.
loop
Use loop filter.
qscale
Use fixed qscale.
pass1
Use internal 2pass ratecontrol in first pass mode.
pass2
Use internal 2pass ratecontrol in second pass mode.
gray
Only decode/encode grayscale.
emu_edge
Do not draw edges.
psnr
Set error[?] variables during encoding.
truncated
ildct
Use interlaced DCT.
low_delay
Force low delay.
global_header
Place global headers in extradata instead of every keyframe.
bitexact
Only write platform-, build- and time-independent data. (except
(I)DCT). This ensures that file and data checksums are
reproducible and match between platforms. Its primary use is
for regression testing.
aic Apply H263 advanced intra coding / mpeg4 ac prediction.
cbp Deprecated, use mpegvideo private options instead.
qprd
Deprecated, use mpegvideo private options instead.
ilme
Apply interlaced motion estimation.
cgop
Use closed gop.
me_method integer (encoding,video)
Set motion estimation method.
Possible values:
zero
zero motion estimation (fastest)
full
full motion estimation (slowest)
epzs
EPZS motion estimation (default)
esa esa motion estimation (alias for full)
tesa
tesa motion estimation
dia dia motion estimation (alias for epzs)
log log motion estimation
phods
phods motion estimation
x1 X1 motion estimation
hex hex motion estimation
umh umh motion estimation
iter
iter motion estimation
extradata_size integer
Set extradata size.
time_base rational number
Set codec time base.
It is the fundamental unit of time (in seconds) in terms of which
frame timestamps are represented. For fixed-fps content, timebase
should be "1 / frame_rate" and timestamp increments should be
identically 1.
g integer (encoding,video)
Set the group of picture (GOP) size. Default value is 12.
ar integer (decoding/encoding,audio)
Set audio sampling rate (in Hz).
ac integer (decoding/encoding,audio)
Set number of audio channels.
cutoff integer (encoding,audio)
Set cutoff bandwidth. (Supported only by selected encoders, see
their respective documentation sections.)
frame_size integer (encoding,audio)
Set audio frame size.
Each submitted frame except the last must contain exactly
frame_size samples per channel. May be 0 when the codec has
CODEC_CAP_VARIABLE_FRAME_SIZE set, in that case the frame size is
not restricted. It is set by some decoders to indicate constant
frame size.
frame_number integer
Set the frame number.
delay integer
qcomp float (encoding,video)
Set video quantizer scale compression (VBR). It is used as a
constant in the ratecontrol equation. Recommended range for default
rc_eq: 0.0-1.0.
qblur float (encoding,video)
Set video quantizer scale blur (VBR).
qmin integer (encoding,video)
Set min video quantizer scale (VBR). Must be included between -1
and 69, default value is 2.
qmax integer (encoding,video)
Set max video quantizer scale (VBR). Must be included between -1
and 1024, default value is 31.
qdiff integer (encoding,video)
Set max difference between the quantizer scale (VBR).
bf integer (encoding,video)
Set max number of B frames between non-B-frames.
Must be an integer between -1 and 16. 0 means that B-frames are
disabled. If a value of -1 is used, it will choose an automatic
value depending on the encoder.
Default value is 0.
b_qfactor float (encoding,video)
Set qp factor between P and B frames.
rc_strategy integer (encoding,video)
Set ratecontrol method.
b_strategy integer (encoding,video)
Set strategy to choose between I/P/B-frames.
ps integer (encoding,video)
Set RTP payload size in bytes.
mv_bits integer
header_bits integer
i_tex_bits integer
p_tex_bits integer
i_count integer
p_count integer
skip_count integer
misc_bits integer
frame_bits integer
codec_tag integer
bug flags (decoding,video)
Workaround not auto detected encoder bugs.
Possible values:
autodetect
old_msmpeg4
some old lavc generated msmpeg4v3 files (no autodetection)
xvid_ilace
Xvid interlacing bug (autodetected if fourcc==XVIX)
ump4
(autodetected if fourcc==UMP4)
no_padding
padding bug (autodetected)
amv
ac_vlc
illegal vlc bug (autodetected per fourcc)
qpel_chroma
std_qpel
old standard qpel (autodetected per fourcc/version)
qpel_chroma2
direct_blocksize
direct-qpel-blocksize bug (autodetected per fourcc/version)
edge
edge padding bug (autodetected per fourcc/version)
hpel_chroma
dc_clip
ms Workaround various bugs in microsoft broken decoders.
trunc
trancated frames
lelim integer (encoding,video)
Set single coefficient elimination threshold for luminance
(negative values also consider DC coefficient).
celim integer (encoding,video)
Set single coefficient elimination threshold for chrominance
(negative values also consider dc coefficient)
strict integer (decoding/encoding,audio,video)
Specify how strictly to follow the standards.
Possible values:
very
strictly conform to an older more strict version of the spec or
reference software
strict
strictly conform to all the things in the spec no matter what
consequences
normal
unofficial
allow unofficial extensions
experimental
allow non standardized experimental things, experimental
(unfinished/work in progress/not well tested) decoders and
encoders. Note: experimental decoders can pose a security
risk, do not use this for decoding untrusted input.
b_qoffset float (encoding,video)
Set QP offset between P and B frames.
err_detect flags (decoding,audio,video)
Set error detection flags.
Possible values:
crccheck
verify embedded CRCs
bitstream
detect bitstream specification deviations
buffer
detect improper bitstream length
explode
abort decoding on minor error detection
ignore_err
ignore decoding errors, and continue decoding. This is useful
if you want to analyze the content of a video and thus want
everything to be decoded no matter what. This option will not
result in a video that is pleasing to watch in case of errors.
careful
consider things that violate the spec and have not been seen in
the wild as errors
compliant
consider all spec non compliancies as errors
aggressive
consider things that a sane encoder should not do as an error
has_b_frames integer
block_align integer
mpeg_quant integer (encoding,video)
Use MPEG quantizers instead of H.263.
qsquish float (encoding,video)
How to keep quantizer between qmin and qmax (0 = clip, 1 = use
differentiable function).
rc_qmod_amp float (encoding,video)
Set experimental quantizer modulation.
rc_qmod_freq integer (encoding,video)
Set experimental quantizer modulation.
rc_override_count integer
rc_eq string (encoding,video)
Set rate control equation. When computing the expression, besides
the standard functions defined in the section 'Expression
Evaluation', the following functions are available: bits2qp(bits),
qp2bits(qp). Also the following constants are available: iTex pTex
tex mv fCode iCount mcVar var isI isP isB avgQP qComp avgIITex
avgPITex avgPPTex avgBPTex avgTex.
maxrate integer (encoding,audio,video)
Set max bitrate tolerance (in bits/s). Requires bufsize to be set.
minrate integer (encoding,audio,video)
Set min bitrate tolerance (in bits/s). Most useful in setting up a
CBR encode. It is of little use elsewise.
bufsize integer (encoding,audio,video)
Set ratecontrol buffer size (in bits).
rc_buf_aggressivity float (encoding,video)
Currently useless.
i_qfactor float (encoding,video)
Set QP factor between P and I frames.
i_qoffset float (encoding,video)
Set QP offset between P and I frames.
rc_init_cplx float (encoding,video)
Set initial complexity for 1-pass encoding.
dct integer (encoding,video)
Set DCT algorithm.
Possible values:
auto
autoselect a good one (default)
fastint
fast integer
int accurate integer
mmx
altivec
faan
floating point AAN DCT
lumi_mask float (encoding,video)
Compress bright areas stronger than medium ones.
tcplx_mask float (encoding,video)
Set temporal complexity masking.
scplx_mask float (encoding,video)
Set spatial complexity masking.
p_mask float (encoding,video)
Set inter masking.
dark_mask float (encoding,video)
Compress dark areas stronger than medium ones.
idct integer (decoding/encoding,video)
Select IDCT implementation.
Possible values:
auto
int
simple
simplemmx
simpleauto
Automatically pick a IDCT compatible with the simple one
arm
altivec
sh4
simplearm
simplearmv5te
simplearmv6
simpleneon
simplealpha
ipp
xvidmmx
faani
floating point AAN IDCT
slice_count integer
ec flags (decoding,video)
Set error concealment strategy.
Possible values:
guess_mvs
iterative motion vector (MV) search (slow)
deblock
use strong deblock filter for damaged MBs
favor_inter
favor predicting from the previous frame instead of the current
bits_per_coded_sample integer
pred integer (encoding,video)
Set prediction method.
Possible values:
left
plane
median
aspect rational number (encoding,video)
Set sample aspect ratio.
sar rational number (encoding,video)
Set sample aspect ratio. Alias to aspect.
debug flags (decoding/encoding,audio,video,subtitles)
Print specific debug info.
Possible values:
pict
picture info
rc rate control
bitstream
mb_type
macroblock (MB) type
qp per-block quantization parameter (QP)
dct_coeff
green_metadata
display complexity metadata for the upcoming frame, GoP or for
a given duration.
skip
startcode
er error recognition
mmco
memory management control operations (H.264)
bugs
buffers
picture buffer allocations
thread_ops
threading operations
nomc
skip motion compensation
cmp integer (encoding,video)
Set full pel me compare function.
Possible values:
sad sum of absolute differences, fast (default)
sse sum of squared errors
satd
sum of absolute Hadamard transformed differences
dct sum of absolute DCT transformed differences
psnr
sum of squared quantization errors (avoid, low quality)
bit number of bits needed for the block
rd rate distortion optimal, slow
zero
0
vsad
sum of absolute vertical differences
vsse
sum of squared vertical differences
nsse
noise preserving sum of squared differences
w53 5/3 wavelet, only used in snow
w97 9/7 wavelet, only used in snow
dctmax
chroma
subcmp integer (encoding,video)
Set sub pel me compare function.
Possible values:
sad sum of absolute differences, fast (default)
sse sum of squared errors
satd
sum of absolute Hadamard transformed differences
dct sum of absolute DCT transformed differences
psnr
sum of squared quantization errors (avoid, low quality)
bit number of bits needed for the block
rd rate distortion optimal, slow
zero
0
vsad
sum of absolute vertical differences
vsse
sum of squared vertical differences
nsse
noise preserving sum of squared differences
w53 5/3 wavelet, only used in snow
w97 9/7 wavelet, only used in snow
dctmax
chroma
mbcmp integer (encoding,video)
Set macroblock compare function.
Possible values:
sad sum of absolute differences, fast (default)
sse sum of squared errors
satd
sum of absolute Hadamard transformed differences
dct sum of absolute DCT transformed differences
psnr
sum of squared quantization errors (avoid, low quality)
bit number of bits needed for the block
rd rate distortion optimal, slow
zero
0
vsad
sum of absolute vertical differences
vsse
sum of squared vertical differences
nsse
noise preserving sum of squared differences
w53 5/3 wavelet, only used in snow
w97 9/7 wavelet, only used in snow
dctmax
chroma
ildctcmp integer (encoding,video)
Set interlaced dct compare function.
Possible values:
sad sum of absolute differences, fast (default)
sse sum of squared errors
satd
sum of absolute Hadamard transformed differences
dct sum of absolute DCT transformed differences
psnr
sum of squared quantization errors (avoid, low quality)
bit number of bits needed for the block
rd rate distortion optimal, slow
zero
0
vsad
sum of absolute vertical differences
vsse
sum of squared vertical differences
nsse
noise preserving sum of squared differences
w53 5/3 wavelet, only used in snow
w97 9/7 wavelet, only used in snow
dctmax
chroma
dia_size integer (encoding,video)
Set diamond type & size for motion estimation.
last_pred integer (encoding,video)
Set amount of motion predictors from the previous frame.
preme integer (encoding,video)
Set pre motion estimation.
precmp integer (encoding,video)
Set pre motion estimation compare function.
Possible values:
sad sum of absolute differences, fast (default)
sse sum of squared errors
satd
sum of absolute Hadamard transformed differences
dct sum of absolute DCT transformed differences
psnr
sum of squared quantization errors (avoid, low quality)
bit number of bits needed for the block
rd rate distortion optimal, slow
zero
0
vsad
sum of absolute vertical differences
vsse
sum of squared vertical differences
nsse
noise preserving sum of squared differences
w53 5/3 wavelet, only used in snow
w97 9/7 wavelet, only used in snow
dctmax
chroma
pre_dia_size integer (encoding,video)
Set diamond type & size for motion estimation pre-pass.
subq integer (encoding,video)
Set sub pel motion estimation quality.
dtg_active_format integer
me_range integer (encoding,video)
Set limit motion vectors range (1023 for DivX player).
ibias integer (encoding,video)
Set intra quant bias.
pbias integer (encoding,video)
Set inter quant bias.
color_table_id integer
global_quality integer (encoding,audio,video)
coder integer (encoding,video)
Possible values:
vlc variable length coder / huffman coder
ac arithmetic coder
raw raw (no encoding)
rle run-length coder
deflate
deflate-based coder
context integer (encoding,video)
Set context model.
slice_flags integer
mbd integer (encoding,video)
Set macroblock decision algorithm (high quality mode).
Possible values:
simple
use mbcmp (default)
bits
use fewest bits
rd use best rate distortion
stream_codec_tag integer
sc_threshold integer (encoding,video)
Set scene change threshold.
lmin integer (encoding,video)
Set min lagrange factor (VBR).
lmax integer (encoding,video)
Set max lagrange factor (VBR).
nr integer (encoding,video)
Set noise reduction.
rc_init_occupancy integer (encoding,video)
Set number of bits which should be loaded into the rc buffer before
decoding starts.
flags2 flags (decoding/encoding,audio,video)
Possible values:
fast
Allow non spec compliant speedup tricks.
sgop
Deprecated, use mpegvideo private options instead.
noout
Skip bitstream encoding.
ignorecrop
Ignore cropping information from sps.
local_header
Place global headers at every keyframe instead of in extradata.
chunks
Frame data might be split into multiple chunks.
showall
Show all frames before the first keyframe.
skiprd
Deprecated, use mpegvideo private options instead.
export_mvs
Export motion vectors into frame side-data (see
"AV_FRAME_DATA_MOTION_VECTORS") for codecs that support it. See
also doc/examples/export_mvs.c.
error integer (encoding,video)
qns integer (encoding,video)
Deprecated, use mpegvideo private options instead.
threads integer (decoding/encoding,video)
Set the number of threads to be used, in case the selected codec
implementation supports multi-threading.
Possible values:
auto, 0
automatically select the number of threads to set
Default value is auto.
me_threshold integer (encoding,video)
Set motion estimation threshold.
mb_threshold integer (encoding,video)
Set macroblock threshold.
dc integer (encoding,video)
Set intra_dc_precision.
nssew integer (encoding,video)
Set nsse weight.
skip_top integer (decoding,video)
Set number of macroblock rows at the top which are skipped.
skip_bottom integer (decoding,video)
Set number of macroblock rows at the bottom which are skipped.
profile integer (encoding,audio,video)
Possible values:
unknown
aac_main
aac_low
aac_ssr
aac_ltp
aac_he
aac_he_v2
aac_ld
aac_eld
mpeg2_aac_low
mpeg2_aac_he
mpeg4_sp
mpeg4_core
mpeg4_main
mpeg4_asp
dts
dts_es
dts_96_24
dts_hd_hra
dts_hd_ma
level integer (encoding,audio,video)
Possible values:
unknown
lowres integer (decoding,audio,video)
Decode at 1= 1/2, 2=1/4, 3=1/8 resolutions.
skip_threshold integer (encoding,video)
Set frame skip threshold.
skip_factor integer (encoding,video)
Set frame skip factor.
skip_exp integer (encoding,video)
Set frame skip exponent. Negative values behave identical to the
corresponding positive ones, except that the score is normalized.
Positive values exist primarily for compatibility reasons and are
not so useful.
skipcmp integer (encoding,video)
Set frame skip compare function.
Possible values:
sad sum of absolute differences, fast (default)
sse sum of squared errors
satd
sum of absolute Hadamard transformed differences
dct sum of absolute DCT transformed differences
psnr
sum of squared quantization errors (avoid, low quality)
bit number of bits needed for the block
rd rate distortion optimal, slow
zero
0
vsad
sum of absolute vertical differences
vsse
sum of squared vertical differences
nsse
noise preserving sum of squared differences
w53 5/3 wavelet, only used in snow
w97 9/7 wavelet, only used in snow
dctmax
chroma
border_mask float (encoding,video)
Increase the quantizer for macroblocks close to borders.
mblmin integer (encoding,video)
Set min macroblock lagrange factor (VBR).
mblmax integer (encoding,video)
Set max macroblock lagrange factor (VBR).
mepc integer (encoding,video)
Set motion estimation bitrate penalty compensation (1.0 = 256).
skip_loop_filter integer (decoding,video)
skip_idct integer (decoding,video)
skip_frame integer (decoding,video)
Make decoder discard processing depending on the frame type
selected by the option value.
skip_loop_filter skips frame loop filtering, skip_idct skips frame
IDCT/dequantization, skip_frame skips decoding.
Possible values:
none
Discard no frame.
default
Discard useless frames like 0-sized frames.
noref
Discard all non-reference frames.
bidir
Discard all bidirectional frames.
nokey
Discard all frames excepts keyframes.
all Discard all frames.
Default value is default.
bidir_refine integer (encoding,video)
Refine the two motion vectors used in bidirectional macroblocks.
brd_scale integer (encoding,video)
Downscale frames for dynamic B-frame decision.
keyint_min integer (encoding,video)
Set minimum interval between IDR-frames.
refs integer (encoding,video)
Set reference frames to consider for motion compensation.
chromaoffset integer (encoding,video)
Set chroma qp offset from luma.
trellis integer (encoding,audio,video)
Set rate-distortion optimal quantization.
mv0_threshold integer (encoding,video)
b_sensitivity integer (encoding,video)
Adjust sensitivity of b_frame_strategy 1.
compression_level integer (encoding,audio,video)
min_prediction_order integer (encoding,audio)
max_prediction_order integer (encoding,audio)
timecode_frame_start integer (encoding,video)
Set GOP timecode frame start number, in non drop frame format.
request_channels integer (decoding,audio)
Set desired number of audio channels.
bits_per_raw_sample integer
channel_layout integer (decoding/encoding,audio)
Possible values:
request_channel_layout integer (decoding,audio)
Possible values:
rc_max_vbv_use float (encoding,video)
rc_min_vbv_use float (encoding,video)
ticks_per_frame integer (decoding/encoding,audio,video)
color_primaries integer (decoding/encoding,video)
Possible values:
bt709
BT.709
bt470m
BT.470 M
bt470bg
BT.470 BG
smpte170m
SMPTE 170 M
smpte240m
SMPTE 240 M
film
Film
bt2020
BT.2020
smpte428
smpte428_1
SMPTE ST 428-1
smpte431
SMPTE 431-2
smpte432
SMPTE 432-1
jedec-p22
JEDEC P22
color_trc integer (decoding/encoding,video)
Possible values:
bt709
BT.709
gamma22
BT.470 M
gamma28
BT.470 BG
smpte170m
SMPTE 170 M
smpte240m
SMPTE 240 M
linear
Linear
log
log100
Log
log_sqrt
log316
Log square root
iec61966_2_4
iec61966-2-4
IEC 61966-2-4
bt1361
bt1361e
BT.1361
iec61966_2_1
iec61966-2-1
IEC 61966-2-1
bt2020_10
bt2020_10bit
BT.2020 - 10 bit
bt2020_12
bt2020_12bit
BT.2020 - 12 bit
smpte2084
SMPTE ST 2084
smpte428
smpte428_1
SMPTE ST 428-1
arib-std-b67
ARIB STD-B67
colorspace integer (decoding/encoding,video)
Possible values:
rgb RGB
bt709
BT.709
fcc FCC
bt470bg
BT.470 BG
smpte170m
SMPTE 170 M
smpte240m
SMPTE 240 M
ycocg
YCOCG
bt2020nc
bt2020_ncl
BT.2020 NCL
bt2020c
bt2020_cl
BT.2020 CL
smpte2085
SMPTE 2085
color_range integer (decoding/encoding,video)
If used as input parameter, it serves as a hint to the decoder,
which color_range the input has. Possible values:
tv
mpeg
MPEG (219*2^(n-8))
pc
jpeg
JPEG (2^n-1)
chroma_sample_location integer (decoding/encoding,video)
Possible values:
left
center
topleft
top
bottomleft
bottom
log_level_offset integer
Set the log level offset.
slices integer (encoding,video)
Number of slices, used in parallelized encoding.
thread_type flags (decoding/encoding,video)
Select which multithreading methods to use.
Use of frame will increase decoding delay by one frame per thread,
so clients which cannot provide future frames should not use it.
Possible values:
slice
Decode more than one part of a single frame at once.
Multithreading using slices works only when the video was
encoded with slices.
frame
Decode more than one frame at once.
Default value is slice+frame.
audio_service_type integer (encoding,audio)
Set audio service type.
Possible values:
ma Main Audio Service
ef Effects
vi Visually Impaired
hi Hearing Impaired
di Dialogue
co Commentary
em Emergency
vo Voice Over
ka Karaoke
request_sample_fmt sample_fmt (decoding,audio)
Set sample format audio decoders should prefer. Default value is
"none".
pkt_timebase rational number
sub_charenc encoding (decoding,subtitles)
Set the input subtitles character encoding.
field_order field_order (video)
Set/override the field order of the video. Possible values:
progressive
Progressive video
tt Interlaced video, top field coded and displayed first
bb Interlaced video, bottom field coded and displayed first
tb Interlaced video, top coded first, bottom displayed first
bt Interlaced video, bottom coded first, top displayed first
skip_alpha bool (decoding,video)
Set to 1 to disable processing alpha (transparency). This works
like the gray flag in the flags option which skips chroma
information instead of alpha. Default is 0.
codec_whitelist list (input)
"," separated list of allowed decoders. By default all are allowed.
dump_separator string (input)
Separator used to separate the fields printed on the command line
about the Stream parameters. For example to separate the fields
with newlines and indention:
ffprobe -dump_separator "
" -i ~/videos/matrixbench_mpeg2.mpg
max_pixels integer (decoding/encoding,video)
Maximum number of pixels per image. This value can be used to avoid
out of memory failures due to large images.
apply_cropping bool (decoding,video)
Enable cropping if cropping parameters are multiples of the
required alignment for the left and top parameters. If the
alignment is not met the cropping will be partially applied to
maintain alignment. Default is 1 (enabled). Note: The required
alignment depends on if "AV_CODEC_FLAG_UNALIGNED" is set and the
CPU. "AV_CODEC_FLAG_UNALIGNED" cannot be changed from the command
line. Also hardware decoders will not apply left/top Cropping.
DECODERS
Decoders are configured elements in FFmpeg which allow the decoding of
multimedia streams.
When you configure your FFmpeg build, all the supported native decoders
are enabled by default. Decoders requiring an external library must be
enabled manually via the corresponding "--enable-lib" option. You can
list all available decoders using the configure option
"--list-decoders".
You can disable all the decoders with the configure option
"--disable-decoders" and selectively enable / disable single decoders
with the options "--enable-decoder=DECODER" /
"--disable-decoder=DECODER".
The option "-decoders" of the ff* tools will display the list of
enabled decoders.
VIDEO DECODERS
A description of some of the currently available video decoders
follows.
rawvideo
Raw video decoder.
This decoder decodes rawvideo streams.
Options
top top_field_first
Specify the assumed field type of the input video.
-1 the video is assumed to be progressive (default)
0 bottom-field-first is assumed
1 top-field-first is assumed
libdavs2
AVS2-P2/IEEE1857.4 video decoder wrapper.
This decoder allows libavcodec to decode AVS2 streams with davs2
library.
AUDIO DECODERS
A description of some of the currently available audio decoders
follows.
ac3
AC-3 audio decoder.
This decoder implements part of ATSC A/52:2010 and ETSI TS 102 366, as
well as the undocumented RealAudio 3 (a.k.a. dnet).
AC-3 Decoder Options
-drc_scale value
Dynamic Range Scale Factor. The factor to apply to dynamic range
values from the AC-3 stream. This factor is applied exponentially.
There are 3 notable scale factor ranges:
drc_scale == 0
DRC disabled. Produces full range audio.
0 < drc_scale <= 1
DRC enabled. Applies a fraction of the stream DRC value.
Audio reproduction is between full range and full compression.
drc_scale > 1
DRC enabled. Applies drc_scale asymmetrically. Loud sounds are
fully compressed. Soft sounds are enhanced.
flac
FLAC audio decoder.
This decoder aims to implement the complete FLAC specification from
Xiph.
FLAC Decoder options
-use_buggy_lpc
The lavc FLAC encoder used to produce buggy streams with high lpc
values (like the default value). This option makes it possible to
decode such streams correctly by using lavc's old buggy lpc logic
for decoding.
ffwavesynth
Internal wave synthesizer.
This decoder generates wave patterns according to predefined sequences.
Its use is purely internal and the format of the data it accepts is not
publicly documented.
libcelt
libcelt decoder wrapper.
libcelt allows libavcodec to decode the Xiph CELT ultra-low delay audio
codec. Requires the presence of the libcelt headers and library during
configuration. You need to explicitly configure the build with
"--enable-libcelt".
libgsm
libgsm decoder wrapper.
libgsm allows libavcodec to decode the GSM full rate audio codec.
Requires the presence of the libgsm headers and library during
configuration. You need to explicitly configure the build with
"--enable-libgsm".
This decoder supports both the ordinary GSM and the Microsoft variant.
libilbc
libilbc decoder wrapper.
libilbc allows libavcodec to decode the Internet Low Bitrate Codec
(iLBC) audio codec. Requires the presence of the libilbc headers and
library during configuration. You need to explicitly configure the
build with "--enable-libilbc".
Options
The following option is supported by the libilbc wrapper.
enhance
Enable the enhancement of the decoded audio when set to 1. The
default value is 0 (disabled).
libopencore-amrnb
libopencore-amrnb decoder wrapper.
libopencore-amrnb allows libavcodec to decode the Adaptive Multi-Rate
Narrowband audio codec. Using it requires the presence of the
libopencore-amrnb headers and library during configuration. You need to
explicitly configure the build with "--enable-libopencore-amrnb".
An FFmpeg native decoder for AMR-NB exists, so users can decode AMR-NB
without this library.
libopencore-amrwb
libopencore-amrwb decoder wrapper.
libopencore-amrwb allows libavcodec to decode the Adaptive Multi-Rate
Wideband audio codec. Using it requires the presence of the
libopencore-amrwb headers and library during configuration. You need to
explicitly configure the build with "--enable-libopencore-amrwb".
An FFmpeg native decoder for AMR-WB exists, so users can decode AMR-WB
without this library.
libopus
libopus decoder wrapper.
libopus allows libavcodec to decode the Opus Interactive Audio Codec.
Requires the presence of the libopus headers and library during
configuration. You need to explicitly configure the build with
"--enable-libopus".
An FFmpeg native decoder for Opus exists, so users can decode Opus
without this library.
SUBTITLES DECODERS
dvbsub
Options
compute_clut
-1 Compute clut if no matching CLUT is in the stream.
0 Never compute CLUT
1 Always compute CLUT and override the one provided in the
stream.
dvb_substream
Selects the dvb substream, or all substreams if -1 which is
default.
dvdsub
This codec decodes the bitmap subtitles used in DVDs; the same
subtitles can also be found in VobSub file pairs and in some Matroska
files.
Options
palette
Specify the global palette used by the bitmaps. When stored in
VobSub, the palette is normally specified in the index file; in
Matroska, the palette is stored in the codec extra-data in the same
format as in VobSub. In DVDs, the palette is stored in the IFO
file, and therefore not available when reading from dumped VOB
files.
The format for this option is a string containing 16 24-bits
hexadecimal numbers (without 0x prefix) separated by comas, for
example "0d00ee, ee450d, 101010, eaeaea, 0ce60b, ec14ed, ebff0b,
0d617a, 7b7b7b, d1d1d1, 7b2a0e, 0d950c, 0f007b, cf0dec, cfa80c,
7c127b".
ifo_palette
Specify the IFO file from which the global palette is obtained.
(experimental)
forced_subs_only
Only decode subtitle entries marked as forced. Some titles have
forced and non-forced subtitles in the same track. Setting this
flag to 1 will only keep the forced subtitles. Default value is 0.
libzvbi-teletext
Libzvbi allows libavcodec to decode DVB teletext pages and DVB teletext
subtitles. Requires the presence of the libzvbi headers and library
during configuration. You need to explicitly configure the build with
"--enable-libzvbi".
Options
txt_page
List of teletext page numbers to decode. Pages that do not match
the specified list are dropped. You may use the special "*" string
to match all pages, or "subtitle" to match all subtitle pages.
Default value is *.
txt_chop_top
Discards the top teletext line. Default value is 1.
txt_format
Specifies the format of the decoded subtitles.
bitmap
The default format, you should use this for teletext pages,
because certain graphics and colors cannot be expressed in
simple text or even ASS.
text
Simple text based output without formatting.
ass Formatted ASS output, subtitle pages and teletext pages are
returned in different styles, subtitle pages are stripped down
to text, but an effort is made to keep the text alignment and
the formatting.
txt_left
X offset of generated bitmaps, default is 0.
txt_top
Y offset of generated bitmaps, default is 0.
txt_chop_spaces
Chops leading and trailing spaces and removes empty lines from the
generated text. This option is useful for teletext based subtitles
where empty spaces may be present at the start or at the end of the
lines or empty lines may be present between the subtitle lines
because of double-sized teletext characters. Default value is 1.
txt_duration
Sets the display duration of the decoded teletext pages or
subtitles in milliseconds. Default value is -1 which means infinity
or until the next subtitle event comes.
txt_transparent
Force transparent background of the generated teletext bitmaps.
Default value is 0 which means an opaque background.
txt_opacity
Sets the opacity (0-255) of the teletext background. If
txt_transparent is not set, it only affects characters between a
start box and an end box, typically subtitles. Default value is 0
if txt_transparent is set, 255 otherwise.
ENCODERS
Encoders are configured elements in FFmpeg which allow the encoding of
multimedia streams.
When you configure your FFmpeg build, all the supported native encoders
are enabled by default. Encoders requiring an external library must be
enabled manually via the corresponding "--enable-lib" option. You can
list all available encoders using the configure option
"--list-encoders".
You can disable all the encoders with the configure option
"--disable-encoders" and selectively enable / disable single encoders
with the options "--enable-encoder=ENCODER" /
"--disable-encoder=ENCODER".
The option "-encoders" of the ff* tools will display the list of
enabled encoders.
AUDIO ENCODERS
A description of some of the currently available audio encoders
follows.
aac
Advanced Audio Coding (AAC) encoder.
This encoder is the default AAC encoder, natively implemented into
FFmpeg. Its quality is on par or better than libfdk_aac at the default
bitrate of 128kbps. This encoder also implements more options,
profiles and samplerates than other encoders (with only the AAC-HE
profile pending to be implemented) so this encoder has become the
default and is the recommended choice.
Options
b Set bit rate in bits/s. Setting this automatically activates
constant bit rate (CBR) mode. If this option is unspecified it is
set to 128kbps.
q Set quality for variable bit rate (VBR) mode. This option is valid
only using the ffmpeg command-line tool. For library interface
users, use global_quality.
cutoff
Set cutoff frequency. If unspecified will allow the encoder to
dynamically adjust the cutoff to improve clarity on low bitrates.
aac_coder
Set AAC encoder coding method. Possible values:
twoloop
Two loop searching (TLS) method.
This method first sets quantizers depending on band thresholds
and then tries to find an optimal combination by adding or
subtracting a specific value from all quantizers and adjusting
some individual quantizer a little. Will tune itself based on
whether aac_is, aac_ms and aac_pns are enabled.
anmr
Average noise to mask ratio (ANMR) trellis-based solution.
This is an experimental coder which currently produces a lower
quality, is more unstable and is slower than the default
twoloop coder but has potential. Currently has no support for
the aac_is or aac_pns options. Not currently recommended.
fast
Constant quantizer method.
Uses a cheaper version of twoloop algorithm that doesn't try to
do as many clever adjustments. Worse with low bitrates (less
than 64kbps), but is better and much faster at higher bitrates.
This is the default choice for a coder
aac_ms
Sets mid/side coding mode. The default value of "auto" will
automatically use M/S with bands which will benefit from such
coding. Can be forced for all bands using the value "enable", which
is mainly useful for debugging or disabled using "disable".
aac_is
Sets intensity stereo coding tool usage. By default, it's enabled
and will automatically toggle IS for similar pairs of stereo bands
if it's beneficial. Can be disabled for debugging by setting the
value to "disable".
aac_pns
Uses perceptual noise substitution to replace low entropy high
frequency bands with imperceptible white noise during the decoding
process. By default, it's enabled, but can be disabled for
debugging purposes by using "disable".
aac_tns
Enables the use of a multitap FIR filter which spans through the
high frequency bands to hide quantization noise during the encoding
process and is reverted by the decoder. As well as decreasing
unpleasant artifacts in the high range this also reduces the
entropy in the high bands and allows for more bits to be used by
the mid-low bands. By default it's enabled but can be disabled for
debugging by setting the option to "disable".
aac_ltp
Enables the use of the long term prediction extension which
increases coding efficiency in very low bandwidth situations such
as encoding of voice or solo piano music by extending constant
harmonic peaks in bands throughout frames. This option is implied
by profile:a aac_low and is incompatible with aac_pred. Use in
conjunction with -ar to decrease the samplerate.
aac_pred
Enables the use of a more traditional style of prediction where the
spectral coefficients transmitted are replaced by the difference of
the current coefficients minus the previous "predicted"
coefficients. In theory and sometimes in practice this can improve
quality for low to mid bitrate audio. This option implies the
aac_main profile and is incompatible with aac_ltp.
profile
Sets the encoding profile, possible values:
aac_low
The default, AAC "Low-complexity" profile. Is the most
compatible and produces decent quality.
mpeg2_aac_low
Equivalent to "-profile:a aac_low -aac_pns 0". PNS was
introduced with the MPEG4 specifications.
aac_ltp
Long term prediction profile, is enabled by and will enable the
aac_ltp option. Introduced in MPEG4.
aac_main
Main-type prediction profile, is enabled by and will enable the
aac_pred option. Introduced in MPEG2.
If this option is unspecified it is set to aac_low.
ac3 and ac3_fixed
AC-3 audio encoders.
These encoders implement part of ATSC A/52:2010 and ETSI TS 102 366, as
well as the undocumented RealAudio 3 (a.k.a. dnet).
The ac3 encoder uses floating-point math, while the ac3_fixed encoder
only uses fixed-point integer math. This does not mean that one is
always faster, just that one or the other may be better suited to a
particular system. The floating-point encoder will generally produce
better quality audio for a given bitrate. The ac3_fixed encoder is not
the default codec for any of the output formats, so it must be
specified explicitly using the option "-acodec ac3_fixed" in order to
use it.
AC-3 Metadata
The AC-3 metadata options are used to set parameters that describe the
audio, but in most cases do not affect the audio encoding itself. Some
of the options do directly affect or influence the decoding and
playback of the resulting bitstream, while others are just for
informational purposes. A few of the options will add bits to the
output stream that could otherwise be used for audio data, and will
thus affect the quality of the output. Those will be indicated
accordingly with a note in the option list below.
These parameters are described in detail in several publicly-available
documents.
*<<http://www.atsc.org/cms/standards/a_52-2010.pdf>>
*<<http://www.atsc.org/cms/standards/a_54a_with_corr_1.pdf>>
*<<http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/18_Metadata.Guide.pdf>>
*<<http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/46_DDEncodingGuidelines.pdf>>
Metadata Control Options
-per_frame_metadata boolean
Allow Per-Frame Metadata. Specifies if the encoder should check for
changing metadata for each frame.
0 The metadata values set at initialization will be used for
every frame in the stream. (default)
1 Metadata values can be changed before encoding each frame.
Downmix Levels
-center_mixlev level
Center Mix Level. The amount of gain the decoder should apply to
the center channel when downmixing to stereo. This field will only
be written to the bitstream if a center channel is present. The
value is specified as a scale factor. There are 3 valid values:
0.707
Apply -3dB gain
0.595
Apply -4.5dB gain (default)
0.500
Apply -6dB gain
-surround_mixlev level
Surround Mix Level. The amount of gain the decoder should apply to
the surround channel(s) when downmixing to stereo. This field will
only be written to the bitstream if one or more surround channels
are present. The value is specified as a scale factor. There are 3
valid values:
0.707
Apply -3dB gain
0.500
Apply -6dB gain (default)
0.000
Silence Surround Channel(s)
Audio Production Information
Audio Production Information is optional information describing the
mixing environment. Either none or both of the fields are written to
the bitstream.
-mixing_level number
Mixing Level. Specifies peak sound pressure level (SPL) in the
production environment when the mix was mastered. Valid values are
80 to 111, or -1 for unknown or not indicated. The default value is
-1, but that value cannot be used if the Audio Production
Information is written to the bitstream. Therefore, if the
"room_type" option is not the default value, the "mixing_level"
option must not be -1.
-room_type type
Room Type. Describes the equalization used during the final mixing
session at the studio or on the dubbing stage. A large room is a
dubbing stage with the industry standard X-curve equalization; a
small room has flat equalization. This field will not be written
to the bitstream if both the "mixing_level" option and the
"room_type" option have the default values.
0
notindicated
Not Indicated (default)
1
large
Large Room
2
small
Small Room
Other Metadata Options
-copyright boolean
Copyright Indicator. Specifies whether a copyright exists for this
audio.
0
off No Copyright Exists (default)
1
on Copyright Exists
-dialnorm value
Dialogue Normalization. Indicates how far the average dialogue
level of the program is below digital 100% full scale (0 dBFS).
This parameter determines a level shift during audio reproduction
that sets the average volume of the dialogue to a preset level. The
goal is to match volume level between program sources. A value of
-31dB will result in no volume level change, relative to the source
volume, during audio reproduction. Valid values are whole numbers
in the range -31 to -1, with -31 being the default.
-dsur_mode mode
Dolby Surround Mode. Specifies whether the stereo signal uses Dolby
Surround (Pro Logic). This field will only be written to the
bitstream if the audio stream is stereo. Using this option does NOT
mean the encoder will actually apply Dolby Surround processing.
0
notindicated
Not Indicated (default)
1
off Not Dolby Surround Encoded
2
on Dolby Surround Encoded
-original boolean
Original Bit Stream Indicator. Specifies whether this audio is from
the original source and not a copy.
0
off Not Original Source
1
on Original Source (default)
Extended Bitstream Information
The extended bitstream options are part of the Alternate Bit Stream
Syntax as specified in Annex D of the A/52:2010 standard. It is grouped
into 2 parts. If any one parameter in a group is specified, all values
in that group will be written to the bitstream. Default values are
used for those that are written but have not been specified. If the
mixing levels are written, the decoder will use these values instead of
the ones specified in the "center_mixlev" and "surround_mixlev" options
if it supports the Alternate Bit Stream Syntax.
Extended Bitstream Information - Part 1
-dmix_mode mode
Preferred Stereo Downmix Mode. Allows the user to select either
Lt/Rt (Dolby Surround) or Lo/Ro (normal stereo) as the preferred
stereo downmix mode.
0
notindicated
Not Indicated (default)
1
ltrt
Lt/Rt Downmix Preferred
2
loro
Lo/Ro Downmix Preferred
-ltrt_cmixlev level
Lt/Rt Center Mix Level. The amount of gain the decoder should apply
to the center channel when downmixing to stereo in Lt/Rt mode.
1.414
Apply +3dB gain
1.189
Apply +1.5dB gain
1.000
Apply 0dB gain
0.841
Apply -1.5dB gain
0.707
Apply -3.0dB gain
0.595
Apply -4.5dB gain (default)
0.500
Apply -6.0dB gain
0.000
Silence Center Channel
-ltrt_surmixlev level
Lt/Rt Surround Mix Level. The amount of gain the decoder should
apply to the surround channel(s) when downmixing to stereo in Lt/Rt
mode.
0.841
Apply -1.5dB gain
0.707
Apply -3.0dB gain
0.595
Apply -4.5dB gain
0.500
Apply -6.0dB gain (default)
0.000
Silence Surround Channel(s)
-loro_cmixlev level
Lo/Ro Center Mix Level. The amount of gain the decoder should apply
to the center channel when downmixing to stereo in Lo/Ro mode.
1.414
Apply +3dB gain
1.189
Apply +1.5dB gain
1.000
Apply 0dB gain
0.841
Apply -1.5dB gain
0.707
Apply -3.0dB gain
0.595
Apply -4.5dB gain (default)
0.500
Apply -6.0dB gain
0.000
Silence Center Channel
-loro_surmixlev level
Lo/Ro Surround Mix Level. The amount of gain the decoder should
apply to the surround channel(s) when downmixing to stereo in Lo/Ro
mode.
0.841
Apply -1.5dB gain
0.707
Apply -3.0dB gain
0.595
Apply -4.5dB gain
0.500
Apply -6.0dB gain (default)
0.000
Silence Surround Channel(s)
Extended Bitstream Information - Part 2
-dsurex_mode mode
Dolby Surround EX Mode. Indicates whether the stream uses Dolby
Surround EX (7.1 matrixed to 5.1). Using this option does NOT mean
the encoder will actually apply Dolby Surround EX processing.
0
notindicated
Not Indicated (default)
1
on Dolby Surround EX Off
2
off Dolby Surround EX On
-dheadphone_mode mode
Dolby Headphone Mode. Indicates whether the stream uses Dolby
Headphone encoding (multi-channel matrixed to 2.0 for use with
headphones). Using this option does NOT mean the encoder will
actually apply Dolby Headphone processing.
0
notindicated
Not Indicated (default)
1
on Dolby Headphone Off
2
off Dolby Headphone On
-ad_conv_type type
A/D Converter Type. Indicates whether the audio has passed through
HDCD A/D conversion.
0
standard
Standard A/D Converter (default)
1
hdcd
HDCD A/D Converter
Other AC-3 Encoding Options
-stereo_rematrixing boolean
Stereo Rematrixing. Enables/Disables use of rematrixing for stereo
input. This is an optional AC-3 feature that increases quality by
selectively encoding the left/right channels as mid/side. This
option is enabled by default, and it is highly recommended that it
be left as enabled except for testing purposes.
cutoff frequency
Set lowpass cutoff frequency. If unspecified, the encoder selects a
default determined by various other encoding parameters.
Floating-Point-Only AC-3 Encoding Options
These options are only valid for the floating-point encoder and do not
exist for the fixed-point encoder due to the corresponding features not
being implemented in fixed-point.
-channel_coupling boolean
Enables/Disables use of channel coupling, which is an optional AC-3
feature that increases quality by combining high frequency
information from multiple channels into a single channel. The per-
channel high frequency information is sent with less accuracy in
both the frequency and time domains. This allows more bits to be
used for lower frequencies while preserving enough information to
reconstruct the high frequencies. This option is enabled by default
for the floating-point encoder and should generally be left as
enabled except for testing purposes or to increase encoding speed.
-1
auto
Selected by Encoder (default)
0
off Disable Channel Coupling
1
on Enable Channel Coupling
-cpl_start_band number
Coupling Start Band. Sets the channel coupling start band, from 1
to 15. If a value higher than the bandwidth is used, it will be
reduced to 1 less than the coupling end band. If auto is used, the
start band will be determined by the encoder based on the bit rate,
sample rate, and channel layout. This option has no effect if
channel coupling is disabled.
-1
auto
Selected by Encoder (default)
flac
FLAC (Free Lossless Audio Codec) Encoder
Options
The following options are supported by FFmpeg's flac encoder.
compression_level
Sets the compression level, which chooses defaults for many other
options if they are not set explicitly. Valid values are from 0 to
12, 5 is the default.
frame_size
Sets the size of the frames in samples per channel.
lpc_coeff_precision
Sets the LPC coefficient precision, valid values are from 1 to 15,
15 is the default.
lpc_type
Sets the first stage LPC algorithm
none
LPC is not used
fixed
fixed LPC coefficients
levinson
cholesky
lpc_passes
Number of passes to use for Cholesky factorization during LPC
analysis
min_partition_order
The minimum partition order
max_partition_order
The maximum partition order
prediction_order_method
estimation
2level
4level
8level
search
Bruteforce search
log
ch_mode
Channel mode
auto
The mode is chosen automatically for each frame
indep
Channels are independently coded
left_side
right_side
mid_side
exact_rice_parameters
Chooses if rice parameters are calculated exactly or approximately.
if set to 1 then they are chosen exactly, which slows the code down
slightly and improves compression slightly.
multi_dim_quant
Multi Dimensional Quantization. If set to 1 then a 2nd stage LPC
algorithm is applied after the first stage to finetune the
coefficients. This is quite slow and slightly improves compression.
opus
Opus encoder.
This is a native FFmpeg encoder for the Opus format. Currently its in
development and only implements the CELT part of the codec. Its quality
is usually worse and at best is equal to the libopus encoder.
Options
b Set bit rate in bits/s. If unspecified it uses the number of
channels and the layout to make a good guess.
opus_delay
Sets the maximum delay in milliseconds. Lower delays than 20ms will
very quickly decrease quality.
libfdk_aac
libfdk-aac AAC (Advanced Audio Coding) encoder wrapper.
The libfdk-aac library is based on the Fraunhofer FDK AAC code from the
Android project.
Requires the presence of the libfdk-aac headers and library during
configuration. You need to explicitly configure the build with
"--enable-libfdk-aac". The library is also incompatible with GPL, so if
you allow the use of GPL, you should configure with "--enable-gpl
--enable-nonfree --enable-libfdk-aac".
This encoder is considered to produce output on par or worse at 128kbps
to the the native FFmpeg AAC encoder but can often produce better
sounding audio at identical or lower bitrates and has support for the
AAC-HE profiles.
VBR encoding, enabled through the vbr or flags +qscale options, is
experimental and only works with some combinations of parameters.
Support for encoding 7.1 audio is only available with libfdk-aac 0.1.3
or higher.
For more information see the fdk-aac project at
<http://sourceforge.net/p/opencore-amr/fdk-aac/>.
Options
The following options are mapped on the shared FFmpeg codec options.
b Set bit rate in bits/s. If the bitrate is not explicitly specified,
it is automatically set to a suitable value depending on the
selected profile.
In case VBR mode is enabled the option is ignored.
ar Set audio sampling rate (in Hz).
channels
Set the number of audio channels.
flags +qscale
Enable fixed quality, VBR (Variable Bit Rate) mode. Note that VBR
is implicitly enabled when the vbr value is positive.
cutoff
Set cutoff frequency. If not specified (or explicitly set to 0) it
will use a value automatically computed by the library. Default
value is 0.
profile
Set audio profile.
The following profiles are recognized:
aac_low
Low Complexity AAC (LC)
aac_he
High Efficiency AAC (HE-AAC)
aac_he_v2
High Efficiency AAC version 2 (HE-AACv2)
aac_ld
Low Delay AAC (LD)
aac_eld
Enhanced Low Delay AAC (ELD)
If not specified it is set to aac_low.
The following are private options of the libfdk_aac encoder.
afterburner
Enable afterburner feature if set to 1, disabled if set to 0. This
improves the quality but also the required processing power.
Default value is 1.
eld_sbr
Enable SBR (Spectral Band Replication) for ELD if set to 1,
disabled if set to 0.
Default value is 0.
signaling
Set SBR/PS signaling style.
It can assume one of the following values:
default
choose signaling implicitly (explicit hierarchical by default,
implicit if global header is disabled)
implicit
implicit backwards compatible signaling
explicit_sbr
explicit SBR, implicit PS signaling
explicit_hierarchical
explicit hierarchical signaling
Default value is default.
latm
Output LATM/LOAS encapsulated data if set to 1, disabled if set to
0.
Default value is 0.
header_period
Set StreamMuxConfig and PCE repetition period (in frames) for
sending in-band configuration buffers within LATM/LOAS transport
layer.
Must be a 16-bits non-negative integer.
Default value is 0.
vbr Set VBR mode, from 1 to 5. 1 is lowest quality (though still pretty
good) and 5 is highest quality. A value of 0 will disable VBR, and
CBR (Constant Bit Rate) is enabled.
Currently only the aac_low profile supports VBR encoding.
VBR modes 1-5 correspond to roughly the following average bit
rates:
1 32 kbps/channel
2 40 kbps/channel
3 48-56 kbps/channel
4 64 kbps/channel
5 about 80-96 kbps/channel
Default value is 0.
Examples
o Use ffmpeg to convert an audio file to VBR AAC in an M4A (MP4)
container:
ffmpeg -i input.wav -codec:a libfdk_aac -vbr 3 output.m4a
o Use ffmpeg to convert an audio file to CBR 64k kbps AAC, using the
High-Efficiency AAC profile:
ffmpeg -i input.wav -c:a libfdk_aac -profile:a aac_he -b:a 64k output.m4a
libmp3lame
LAME (Lame Ain't an MP3 Encoder) MP3 encoder wrapper.
Requires the presence of the libmp3lame headers and library during
configuration. You need to explicitly configure the build with
"--enable-libmp3lame".
See libshine for a fixed-point MP3 encoder, although with a lower
quality.
Options
The following options are supported by the libmp3lame wrapper. The
lame-equivalent of the options are listed in parentheses.
b (-b)
Set bitrate expressed in bits/s for CBR or ABR. LAME "bitrate" is
expressed in kilobits/s.
q (-V)
Set constant quality setting for VBR. This option is valid only
using the ffmpeg command-line tool. For library interface users,
use global_quality.
compression_level (-q)
Set algorithm quality. Valid arguments are integers in the 0-9
range, with 0 meaning highest quality but slowest, and 9 meaning
fastest while producing the worst quality.
cutoff (--lowpass)
Set lowpass cutoff frequency. If unspecified, the encoder
dynamically adjusts the cutoff.
reservoir
Enable use of bit reservoir when set to 1. Default value is 1. LAME
has this enabled by default, but can be overridden by use --nores
option.
joint_stereo (-m j)
Enable the encoder to use (on a frame by frame basis) either L/R
stereo or mid/side stereo. Default value is 1.
abr (--abr)
Enable the encoder to use ABR when set to 1. The lame --abr sets
the target bitrate, while this options only tells FFmpeg to use ABR
still relies on b to set bitrate.
libopencore-amrnb
OpenCORE Adaptive Multi-Rate Narrowband encoder.
Requires the presence of the libopencore-amrnb headers and library
during configuration. You need to explicitly configure the build with
"--enable-libopencore-amrnb --enable-version3".
This is a mono-only encoder. Officially it only supports 8000Hz sample
rate, but you can override it by setting strict to unofficial or lower.
Options
b Set bitrate in bits per second. Only the following bitrates are
supported, otherwise libavcodec will round to the nearest valid
bitrate.
4750
5150
5900
6700
7400
7950
10200
12200
dtx Allow discontinuous transmission (generate comfort noise) when set
to 1. The default value is 0 (disabled).
libopus
libopus Opus Interactive Audio Codec encoder wrapper.
Requires the presence of the libopus headers and library during
configuration. You need to explicitly configure the build with
"--enable-libopus".
Option Mapping
Most libopus options are modelled after the opusenc utility from opus-
tools. The following is an option mapping chart describing options
supported by the libopus wrapper, and their opusenc-equivalent in
parentheses.
b (bitrate)
Set the bit rate in bits/s. FFmpeg's b option is expressed in
bits/s, while opusenc's bitrate in kilobits/s.
vbr (vbr, hard-cbr, and cvbr)
Set VBR mode. The FFmpeg vbr option has the following valid
arguments, with the opusenc equivalent options in parentheses:
off (hard-cbr)
Use constant bit rate encoding.
on (vbr)
Use variable bit rate encoding (the default).
constrained (cvbr)
Use constrained variable bit rate encoding.
compression_level (comp)
Set encoding algorithm complexity. Valid options are integers in
the 0-10 range. 0 gives the fastest encodes but lower quality,
while 10 gives the highest quality but slowest encoding. The
default is 10.
frame_duration (framesize)
Set maximum frame size, or duration of a frame in milliseconds. The
argument must be exactly the following: 2.5, 5, 10, 20, 40, 60.
Smaller frame sizes achieve lower latency but less quality at a
given bitrate. Sizes greater than 20ms are only interesting at
fairly low bitrates. The default is 20ms.
packet_loss (expect-loss)
Set expected packet loss percentage. The default is 0.
application (N.A.)
Set intended application type. Valid options are listed below:
voip
Favor improved speech intelligibility.
audio
Favor faithfulness to the input (the default).
lowdelay
Restrict to only the lowest delay modes.
cutoff (N.A.)
Set cutoff bandwidth in Hz. The argument must be exactly one of the
following: 4000, 6000, 8000, 12000, or 20000, corresponding to
narrowband, mediumband, wideband, super wideband, and fullband
respectively. The default is 0 (cutoff disabled).
mapping_family (mapping_family)
Set channel mapping family to be used by the encoder. The default
value of -1 uses mapping family 0 for mono and stereo inputs, and
mapping family 1 otherwise. The default also disables the surround
masking and LFE bandwidth optimzations in libopus, and requires
that the input contains 8 channels or fewer.
Other values include 0 for mono and stereo, 1 for surround sound
with masking and LFE bandwidth optimizations, and 255 for
independent streams with an unspecified channel layout.
apply_phase_inv (N.A.) (requires libopus >= 1.2)
If set to 0, disables the use of phase inversion for intensity
stereo, improving the quality of mono downmixes, but slightly
reducing normal stereo quality. The default is 1 (phase inversion
enabled).
libshine
Shine Fixed-Point MP3 encoder wrapper.
Shine is a fixed-point MP3 encoder. It has a far better performance on
platforms without an FPU, e.g. armel CPUs, and some phones and tablets.
However, as it is more targeted on performance than quality, it is not
on par with LAME and other production-grade encoders quality-wise.
Also, according to the project's homepage, this encoder may not be free
of bugs as the code was written a long time ago and the project was
dead for at least 5 years.
This encoder only supports stereo and mono input. This is also CBR-
only.
The original project (last updated in early 2007) is at
<http://sourceforge.net/projects/libshine-fxp/>. We only support the
updated fork by the Savonet/Liquidsoap project at
<https://github.com/savonet/shine>.
Requires the presence of the libshine headers and library during
configuration. You need to explicitly configure the build with
"--enable-libshine".
See also libmp3lame.
Options
The following options are supported by the libshine wrapper. The
shineenc-equivalent of the options are listed in parentheses.
b (-b)
Set bitrate expressed in bits/s for CBR. shineenc -b option is
expressed in kilobits/s.
libtwolame
TwoLAME MP2 encoder wrapper.
Requires the presence of the libtwolame headers and library during
configuration. You need to explicitly configure the build with
"--enable-libtwolame".
Options
The following options are supported by the libtwolame wrapper. The
twolame-equivalent options follow the FFmpeg ones and are in
parentheses.
b (-b)
Set bitrate expressed in bits/s for CBR. twolame b option is
expressed in kilobits/s. Default value is 128k.
q (-V)
Set quality for experimental VBR support. Maximum value range is
from -50 to 50, useful range is from -10 to 10. The higher the
value, the better the quality. This option is valid only using the
ffmpeg command-line tool. For library interface users, use
global_quality.
mode (--mode)
Set the mode of the resulting audio. Possible values:
auto
Choose mode automatically based on the input. This is the
default.
stereo
Stereo
joint_stereo
Joint stereo
dual_channel
Dual channel
mono
Mono
psymodel (--psyc-mode)
Set psychoacoustic model to use in encoding. The argument must be
an integer between -1 and 4, inclusive. The higher the value, the
better the quality. The default value is 3.
energy_levels (--energy)
Enable energy levels extensions when set to 1. The default value is
0 (disabled).
error_protection (--protect)
Enable CRC error protection when set to 1. The default value is 0
(disabled).
copyright (--copyright)
Set MPEG audio copyright flag when set to 1. The default value is 0
(disabled).
original (--original)
Set MPEG audio original flag when set to 1. The default value is 0
(disabled).
libvo-amrwbenc
VisualOn Adaptive Multi-Rate Wideband encoder.
Requires the presence of the libvo-amrwbenc headers and library during
configuration. You need to explicitly configure the build with
"--enable-libvo-amrwbenc --enable-version3".
This is a mono-only encoder. Officially it only supports 16000Hz sample
rate, but you can override it by setting strict to unofficial or lower.
Options
b Set bitrate in bits/s. Only the following bitrates are supported,
otherwise libavcodec will round to the nearest valid bitrate.
6600
8850
12650
14250
15850
18250
19850
23050
23850
dtx Allow discontinuous transmission (generate comfort noise) when set
to 1. The default value is 0 (disabled).
libvorbis
libvorbis encoder wrapper.
Requires the presence of the libvorbisenc headers and library during
configuration. You need to explicitly configure the build with
"--enable-libvorbis".
Options
The following options are supported by the libvorbis wrapper. The
oggenc-equivalent of the options are listed in parentheses.
To get a more accurate and extensive documentation of the libvorbis
options, consult the libvorbisenc's and oggenc's documentations. See
<http://xiph.org/vorbis/>, <http://wiki.xiph.org/Vorbis-tools>, and
oggenc(1).
b (-b)
Set bitrate expressed in bits/s for ABR. oggenc -b is expressed in
kilobits/s.
q (-q)
Set constant quality setting for VBR. The value should be a float
number in the range of -1.0 to 10.0. The higher the value, the
better the quality. The default value is 3.0.
This option is valid only using the ffmpeg command-line tool. For
library interface users, use global_quality.
cutoff (--advanced-encode-option lowpass_frequency=N)
Set cutoff bandwidth in Hz, a value of 0 disables cutoff. oggenc's
related option is expressed in kHz. The default value is 0 (cutoff
disabled).
minrate (-m)
Set minimum bitrate expressed in bits/s. oggenc -m is expressed in
kilobits/s.
maxrate (-M)
Set maximum bitrate expressed in bits/s. oggenc -M is expressed in
kilobits/s. This only has effect on ABR mode.
iblock (--advanced-encode-option impulse_noisetune=N)
Set noise floor bias for impulse blocks. The value is a float
number from -15.0 to 0.0. A negative bias instructs the encoder to
pay special attention to the crispness of transients in the encoded
audio. The tradeoff for better transient response is a higher
bitrate.
libwavpack
A wrapper providing WavPack encoding through libwavpack.
Only lossless mode using 32-bit integer samples is supported currently.
Requires the presence of the libwavpack headers and library during
configuration. You need to explicitly configure the build with
"--enable-libwavpack".
Note that a libavcodec-native encoder for the WavPack codec exists so
users can encode audios with this codec without using this encoder. See
wavpackenc.
Options
wavpack command line utility's corresponding options are listed in
parentheses, if any.
frame_size (--blocksize)
Default is 32768.
compression_level
Set speed vs. compression tradeoff. Acceptable arguments are listed
below:
0 (-f)
Fast mode.
1 Normal (default) settings.
2 (-h)
High quality.
3 (-hh)
Very high quality.
4-8 (-hh -xEXTRAPROC)
Same as 3, but with extra processing enabled.
4 is the same as -x2 and 8 is the same as -x6.
mjpeg
Motion JPEG encoder.
Options
huffman
Set the huffman encoding strategy. Possible values:
default
Use the default huffman tables. This is the default strategy.
optimal
Compute and use optimal huffman tables.
wavpack
WavPack lossless audio encoder.
This is a libavcodec-native WavPack encoder. There is also an encoder
based on libwavpack, but there is virtually no reason to use that
encoder.
See also libwavpack.
Options
The equivalent options for wavpack command line utility are listed in
parentheses.
Shared options
The following shared options are effective for this encoder. Only
special notes about this particular encoder will be documented here.
For the general meaning of the options, see the Codec Options chapter.
frame_size (--blocksize)
For this encoder, the range for this option is between 128 and
131072. Default is automatically decided based on sample rate and
number of channel.
For the complete formula of calculating default, see
libavcodec/wavpackenc.c.
compression_level (-f, -h, -hh, and -x)
This option's syntax is consistent with libwavpack's.
Private options
joint_stereo (-j)
Set whether to enable joint stereo. Valid values are:
on (1)
Force mid/side audio encoding.
off (0)
Force left/right audio encoding.
auto
Let the encoder decide automatically.
optimize_mono
Set whether to enable optimization for mono. This option is only
effective for non-mono streams. Available values:
on enabled
off disabled
VIDEO ENCODERS
A description of some of the currently available video encoders
follows.
Hap
Vidvox Hap video encoder.
Options
format integer
Specifies the Hap format to encode.
hap
hap_alpha
hap_q
Default value is hap.
chunks integer
Specifies the number of chunks to split frames into, between 1 and
64. This permits multithreaded decoding of large frames,
potentially at the cost of data-rate. The encoder may modify this
value to divide frames evenly.
Default value is 1.
compressor integer
Specifies the second-stage compressor to use. If set to none,
chunks will be limited to 1, as chunked uncompressed frames offer
no benefit.
none
snappy
Default value is snappy.
jpeg2000
The native jpeg 2000 encoder is lossy by default, the "-q:v" option can
be used to set the encoding quality. Lossless encoding can be selected
with "-pred 1".
Options
format
Can be set to either "j2k" or "jp2" (the default) that makes it
possible to store non-rgb pix_fmts.
libkvazaar
Kvazaar H.265/HEVC encoder.
Requires the presence of the libkvazaar headers and library during
configuration. You need to explicitly configure the build with
--enable-libkvazaar.
Options
b Set target video bitrate in bit/s and enable rate control.
kvazaar-params
Set kvazaar parameters as a list of name=value pairs separated by
commas (,). See kvazaar documentation for a list of options.
libopenh264
Cisco libopenh264 H.264/MPEG-4 AVC encoder wrapper.
This encoder requires the presence of the libopenh264 headers and
library during configuration. You need to explicitly configure the
build with "--enable-libopenh264". The library is detected using pkg-
config.
For more information about the library see <http://www.openh264.org>.
Options
The following FFmpeg global options affect the configurations of the
libopenh264 encoder.
b Set the bitrate (as a number of bits per second).
g Set the GOP size.
maxrate
Set the max bitrate (as a number of bits per second).
flags +global_header
Set global header in the bitstream.
slices
Set the number of slices, used in parallelized encoding. Default
value is 0. This is only used when slice_mode is set to fixed.
slice_mode
Set slice mode. Can assume one of the following possible values:
fixed
a fixed number of slices
rowmb
one slice per row of macroblocks
auto
automatic number of slices according to number of threads
dyn dynamic slicing
Default value is auto.
loopfilter
Enable loop filter, if set to 1 (automatically enabled). To disable
set a value of 0.
profile
Set profile restrictions. If set to the value of main enable CABAC
(set the "SEncParamExt.iEntropyCodingModeFlag" flag to 1).
max_nal_size
Set maximum NAL size in bytes.
allow_skip_frames
Allow skipping frames to hit the target bitrate if set to 1.
libtheora
libtheora Theora encoder wrapper.
Requires the presence of the libtheora headers and library during
configuration. You need to explicitly configure the build with
"--enable-libtheora".
For more information about the libtheora project see
<http://www.theora.org/>.
Options
The following global options are mapped to internal libtheora options
which affect the quality and the bitrate of the encoded stream.
b Set the video bitrate in bit/s for CBR (Constant Bit Rate) mode.
In case VBR (Variable Bit Rate) mode is enabled this option is
ignored.
flags
Used to enable constant quality mode (VBR) encoding through the
qscale flag, and to enable the "pass1" and "pass2" modes.
g Set the GOP size.
global_quality
Set the global quality as an integer in lambda units.
Only relevant when VBR mode is enabled with "flags +qscale". The
value is converted to QP units by dividing it by "FF_QP2LAMBDA",
clipped in the [0 - 10] range, and then multiplied by 6.3 to get a
value in the native libtheora range [0-63]. A higher value
corresponds to a higher quality.
q Enable VBR mode when set to a non-negative value, and set constant
quality value as a double floating point value in QP units.
The value is clipped in the [0-10] range, and then multiplied by
6.3 to get a value in the native libtheora range [0-63].
This option is valid only using the ffmpeg command-line tool. For
library interface users, use global_quality.
Examples
o Set maximum constant quality (VBR) encoding with ffmpeg:
ffmpeg -i INPUT -codec:v libtheora -q:v 10 OUTPUT.ogg
o Use ffmpeg to convert a CBR 1000 kbps Theora video stream:
ffmpeg -i INPUT -codec:v libtheora -b:v 1000k OUTPUT.ogg
libvpx
VP8/VP9 format supported through libvpx.
Requires the presence of the libvpx headers and library during
configuration. You need to explicitly configure the build with
"--enable-libvpx".
Options
The following options are supported by the libvpx wrapper. The
vpxenc-equivalent options or values are listed in parentheses for easy
migration.
To reduce the duplication of documentation, only the private options
and some others requiring special attention are documented here. For
the documentation of the undocumented generic options, see the Codec
Options chapter.
To get more documentation of the libvpx options, invoke the command
ffmpeg -h encoder=libvpx, ffmpeg -h encoder=libvpx-vp9 or vpxenc
--help. Further information is available in the libvpx API
documentation.
b (target-bitrate)
Set bitrate in bits/s. Note that FFmpeg's b option is expressed in
bits/s, while vpxenc's target-bitrate is in kilobits/s.
g (kf-max-dist)
keyint_min (kf-min-dist)
qmin (min-q)
qmax (max-q)
bufsize (buf-sz, buf-optimal-sz)
Set ratecontrol buffer size (in bits). Note vpxenc's options are
specified in milliseconds, the libvpx wrapper converts this value
as follows: "buf-sz = bufsize * 1000 / bitrate", "buf-optimal-sz =
bufsize * 1000 / bitrate * 5 / 6".
rc_init_occupancy (buf-initial-sz)
Set number of bits which should be loaded into the rc buffer before
decoding starts. Note vpxenc's option is specified in milliseconds,
the libvpx wrapper converts this value as follows:
"rc_init_occupancy * 1000 / bitrate".
undershoot-pct
Set datarate undershoot (min) percentage of the target bitrate.
overshoot-pct
Set datarate overshoot (max) percentage of the target bitrate.
skip_threshold (drop-frame)
qcomp (bias-pct)
maxrate (maxsection-pct)
Set GOP max bitrate in bits/s. Note vpxenc's option is specified as
a percentage of the target bitrate, the libvpx wrapper converts
this value as follows: "(maxrate * 100 / bitrate)".
minrate (minsection-pct)
Set GOP min bitrate in bits/s. Note vpxenc's option is specified as
a percentage of the target bitrate, the libvpx wrapper converts
this value as follows: "(minrate * 100 / bitrate)".
minrate, maxrate, b end-usage=cbr
"(minrate == maxrate == bitrate)".
crf (end-usage=cq, cq-level)
tune (tune)
psnr (psnr)
ssim (ssim)
quality, deadline (deadline)
best
Use best quality deadline. Poorly named and quite slow, this
option should be avoided as it may give worse quality output
than good.
good
Use good quality deadline. This is a good trade-off between
speed and quality when used with the cpu-used option.
realtime
Use realtime quality deadline.
speed, cpu-used (cpu-used)
Set quality/speed ratio modifier. Higher values speed up the encode
at the cost of quality.
nr (noise-sensitivity)
static-thresh
Set a change threshold on blocks below which they will be skipped
by the encoder.
slices (token-parts)
Note that FFmpeg's slices option gives the total number of
partitions, while vpxenc's token-parts is given as
"log2(partitions)".
max-intra-rate
Set maximum I-frame bitrate as a percentage of the target bitrate.
A value of 0 means unlimited.
force_key_frames
"VPX_EFLAG_FORCE_KF"
Alternate reference frame related
auto-alt-ref
Enable use of alternate reference frames (2-pass only).
arnr-max-frames
Set altref noise reduction max frame count.
arnr-type
Set altref noise reduction filter type: backward, forward,
centered.
arnr-strength
Set altref noise reduction filter strength.
rc-lookahead, lag-in-frames (lag-in-frames)
Set number of frames to look ahead for frametype and
ratecontrol.
error-resilient
Enable error resiliency features.
VP9-specific options
lossless
Enable lossless mode.
tile-columns
Set number of tile columns to use. Note this is given as
"log2(tile_columns)". For example, 8 tile columns would be
requested by setting the tile-columns option to 3.
tile-rows
Set number of tile rows to use. Note this is given as
"log2(tile_rows)". For example, 4 tile rows would be requested
by setting the tile-rows option to 2.
frame-parallel
Enable frame parallel decodability features.
aq-mode
Set adaptive quantization mode (0: off (default), 1: variance
2: complexity, 3: cyclic refresh, 4: equator360).
colorspace color-space
Set input color space. The VP9 bitstream supports signaling the
following colorspaces:
rgb sRGB
bt709 bt709
unspecified unknown
bt470bg bt601
smpte170m smpte170
smpte240m smpte240
bt2020_ncl bt2020
row-mt boolean
Enable row based multi-threading.
tune-content
Set content type: default (0), screen (1), film (2).
corpus-complexity
Corpus VBR mode is a variant of standard VBR where the
complexity distribution midpoint is passed in rather than
calculated for a specific clip or chunk.
The valid range is [0, 10000]. 0 (default) uses standard VBR.
For more information about libvpx see: <http://www.webmproject.org/>
libwebp
libwebp WebP Image encoder wrapper
libwebp is Google's official encoder for WebP images. It can encode in
either lossy or lossless mode. Lossy images are essentially a wrapper
around a VP8 frame. Lossless images are a separate codec developed by
Google.
Pixel Format
Currently, libwebp only supports YUV420 for lossy and RGB for lossless
due to limitations of the format and libwebp. Alpha is supported for
either mode. Because of API limitations, if RGB is passed in when
encoding lossy or YUV is passed in for encoding lossless, the pixel
format will automatically be converted using functions from libwebp.
This is not ideal and is done only for convenience.
Options
-lossless boolean
Enables/Disables use of lossless mode. Default is 0.
-compression_level integer
For lossy, this is a quality/speed tradeoff. Higher values give
better quality for a given size at the cost of increased encoding
time. For lossless, this is a size/speed tradeoff. Higher values
give smaller size at the cost of increased encoding time. More
specifically, it controls the number of extra algorithms and
compression tools used, and varies the combination of these tools.
This maps to the method option in libwebp. The valid range is 0 to
6. Default is 4.
-qscale float
For lossy encoding, this controls image quality, 0 to 100. For
lossless encoding, this controls the effort and time spent at
compressing more. The default value is 75. Note that for usage via
libavcodec, this option is called global_quality and must be
multiplied by FF_QP2LAMBDA.
-preset type
Configuration preset. This does some automatic settings based on
the general type of the image.
none
Do not use a preset.
default
Use the encoder default.
picture
Digital picture, like portrait, inner shot
photo
Outdoor photograph, with natural lighting
drawing
Hand or line drawing, with high-contrast details
icon
Small-sized colorful images
text
Text-like
libx264, libx264rgb
x264 H.264/MPEG-4 AVC encoder wrapper.
This encoder requires the presence of the libx264 headers and library
during configuration. You need to explicitly configure the build with
"--enable-libx264".
libx264 supports an impressive number of features, including 8x8 and
4x4 adaptive spatial transform, adaptive B-frame placement, CAVLC/CABAC
entropy coding, interlacing (MBAFF), lossless mode, psy optimizations
for detail retention (adaptive quantization, psy-RD, psy-trellis).
Many libx264 encoder options are mapped to FFmpeg global codec options,
while unique encoder options are provided through private options.
Additionally the x264opts and x264-params private options allows one to
pass a list of key=value tuples as accepted by the libx264
"x264_param_parse" function.
The x264 project website is at
<http://www.videolan.org/developers/x264.html>.
The libx264rgb encoder is the same as libx264, except it accepts packed
RGB pixel formats as input instead of YUV.
Supported Pixel Formats
x264 supports 8- to 10-bit color spaces. The exact bit depth is
controlled at x264's configure time. FFmpeg only supports one bit depth
in one particular build. In other words, it is not possible to build
one FFmpeg with multiple versions of x264 with different bit depths.
Options
The following options are supported by the libx264 wrapper. The
x264-equivalent options or values are listed in parentheses for easy
migration.
To reduce the duplication of documentation, only the private options
and some others requiring special attention are documented here. For
the documentation of the undocumented generic options, see the Codec
Options chapter.
To get a more accurate and extensive documentation of the libx264
options, invoke the command x264 --fullhelp or consult the libx264
documentation.
b (bitrate)
Set bitrate in bits/s. Note that FFmpeg's b option is expressed in
bits/s, while x264's bitrate is in kilobits/s.
bf (bframes)
g (keyint)
qmin (qpmin)
Minimum quantizer scale.
qmax (qpmax)
Maximum quantizer scale.
qdiff (qpstep)
Maximum difference between quantizer scales.
qblur (qblur)
Quantizer curve blur
qcomp (qcomp)
Quantizer curve compression factor
refs (ref)
Number of reference frames each P-frame can use. The range is from
0-16.
sc_threshold (scenecut)
Sets the threshold for the scene change detection.
trellis (trellis)
Performs Trellis quantization to increase efficiency. Enabled by
default.
nr (nr)
me_range (merange)
Maximum range of the motion search in pixels.
me_method (me)
Set motion estimation method. Possible values in the decreasing
order of speed:
dia (dia)
epzs (dia)
Diamond search with radius 1 (fastest). epzs is an alias for
dia.
hex (hex)
Hexagonal search with radius 2.
umh (umh)
Uneven multi-hexagon search.
esa (esa)
Exhaustive search.
tesa (tesa)
Hadamard exhaustive search (slowest).
forced-idr
Normally, when forcing a I-frame type, the encoder can select any
type of I-frame. This option forces it to choose an IDR-frame.
subq (subme)
Sub-pixel motion estimation method.
b_strategy (b-adapt)
Adaptive B-frame placement decision algorithm. Use only on first-
pass.
keyint_min (min-keyint)
Minimum GOP size.
coder
Set entropy encoder. Possible values:
ac Enable CABAC.
vlc Enable CAVLC and disable CABAC. It generates the same effect as
x264's --no-cabac option.
cmp Set full pixel motion estimation comparison algorithm. Possible
values:
chroma
Enable chroma in motion estimation.
sad Ignore chroma in motion estimation. It generates the same
effect as x264's --no-chroma-me option.
threads (threads)
Number of encoding threads.
thread_type
Set multithreading technique. Possible values:
slice
Slice-based multithreading. It generates the same effect as
x264's --sliced-threads option.
frame
Frame-based multithreading.
flags
Set encoding flags. It can be used to disable closed GOP and enable
open GOP by setting it to "-cgop". The result is similar to the
behavior of x264's --open-gop option.
rc_init_occupancy (vbv-init)
preset (preset)
Set the encoding preset.
tune (tune)
Set tuning of the encoding params.
profile (profile)
Set profile restrictions.
fastfirstpass
Enable fast settings when encoding first pass, when set to 1. When
set to 0, it has the same effect of x264's --slow-firstpass option.
crf (crf)
Set the quality for constant quality mode.
crf_max (crf-max)
In CRF mode, prevents VBV from lowering quality beyond this point.
qp (qp)
Set constant quantization rate control method parameter.
aq-mode (aq-mode)
Set AQ method. Possible values:
none (0)
Disabled.
variance (1)
Variance AQ (complexity mask).
autovariance (2)
Auto-variance AQ (experimental).
aq-strength (aq-strength)
Set AQ strength, reduce blocking and blurring in flat and textured
areas.
psy Use psychovisual optimizations when set to 1. When set to 0, it has
the same effect as x264's --no-psy option.
psy-rd (psy-rd)
Set strength of psychovisual optimization, in psy-rd:psy-trellis
format.
rc-lookahead (rc-lookahead)
Set number of frames to look ahead for frametype and ratecontrol.
weightb
Enable weighted prediction for B-frames when set to 1. When set to
0, it has the same effect as x264's --no-weightb option.
weightp (weightp)
Set weighted prediction method for P-frames. Possible values:
none (0)
Disabled
simple (1)
Enable only weighted refs
smart (2)
Enable both weighted refs and duplicates
ssim (ssim)
Enable calculation and printing SSIM stats after the encoding.
intra-refresh (intra-refresh)
Enable the use of Periodic Intra Refresh instead of IDR frames when
set to 1.
avcintra-class (class)
Configure the encoder to generate AVC-Intra. Valid values are
50,100 and 200
bluray-compat (bluray-compat)
Configure the encoder to be compatible with the bluray standard.
It is a shorthand for setting "bluray-compat=1 force-cfr=1".
b-bias (b-bias)
Set the influence on how often B-frames are used.
b-pyramid (b-pyramid)
Set method for keeping of some B-frames as references. Possible
values:
none (none)
Disabled.
strict (strict)
Strictly hierarchical pyramid.
normal (normal)
Non-strict (not Blu-ray compatible).
mixed-refs
Enable the use of one reference per partition, as opposed to one
reference per macroblock when set to 1. When set to 0, it has the
same effect as x264's --no-mixed-refs option.
8x8dct
Enable adaptive spatial transform (high profile 8x8 transform) when
set to 1. When set to 0, it has the same effect as x264's
--no-8x8dct option.
fast-pskip
Enable early SKIP detection on P-frames when set to 1. When set to
0, it has the same effect as x264's --no-fast-pskip option.
aud (aud)
Enable use of access unit delimiters when set to 1.
mbtree
Enable use macroblock tree ratecontrol when set to 1. When set to
0, it has the same effect as x264's --no-mbtree option.
deblock (deblock)
Set loop filter parameters, in alpha:beta form.
cplxblur (cplxblur)
Set fluctuations reduction in QP (before curve compression).
partitions (partitions)
Set partitions to consider as a comma-separated list of. Possible
values in the list:
p8x8
8x8 P-frame partition.
p4x4
4x4 P-frame partition.
b8x8
4x4 B-frame partition.
i8x8
8x8 I-frame partition.
i4x4
4x4 I-frame partition. (Enabling p4x4 requires p8x8 to be
enabled. Enabling i8x8 requires adaptive spatial transform
(8x8dct option) to be enabled.)
none (none)
Do not consider any partitions.
all (all)
Consider every partition.
direct-pred (direct)
Set direct MV prediction mode. Possible values:
none (none)
Disable MV prediction.
spatial (spatial)
Enable spatial predicting.
temporal (temporal)
Enable temporal predicting.
auto (auto)
Automatically decided.
slice-max-size (slice-max-size)
Set the limit of the size of each slice in bytes. If not specified
but RTP payload size (ps) is specified, that is used.
stats (stats)
Set the file name for multi-pass stats.
nal-hrd (nal-hrd)
Set signal HRD information (requires vbv-bufsize to be set).
Possible values:
none (none)
Disable HRD information signaling.
vbr (vbr)
Variable bit rate.
cbr (cbr)
Constant bit rate (not allowed in MP4 container).
x264opts (N.A.)
Set any x264 option, see x264 --fullhelp for a list.
Argument is a list of key=value couples separated by ":". In filter
and psy-rd options that use ":" as a separator themselves, use ","
instead. They accept it as well since long ago but this is kept
undocumented for some reason.
For example to specify libx264 encoding options with ffmpeg:
ffmpeg -i foo.mpg -c:v libx264 -x264opts keyint=123:min-keyint=20 -an out.mkv
a53cc boolean
Import closed captions (which must be ATSC compatible format) into
output. Only the mpeg2 and h264 decoders provide these. Default is
1 (on).
x264-params (N.A.)
Override the x264 configuration using a :-separated list of
key=value parameters.
This option is functionally the same as the x264opts, but is
duplicated for compatibility with the Libav fork.
For example to specify libx264 encoding options with ffmpeg:
ffmpeg -i INPUT -c:v libx264 -x264-params level=30:bframes=0:weightp=0:\
cabac=0:ref=1:vbv-maxrate=768:vbv-bufsize=2000:analyse=all:me=umh:\
no-fast-pskip=1:subq=6:8x8dct=0:trellis=0 OUTPUT
Encoding ffpresets for common usages are provided so they can be used
with the general presets system (e.g. passing the pre option).
libx265
x265 H.265/HEVC encoder wrapper.
This encoder requires the presence of the libx265 headers and library
during configuration. You need to explicitly configure the build with
--enable-libx265.
Options
preset
Set the x265 preset.
tune
Set the x265 tune parameter.
profile
Set profile restrictions.
crf Set the quality for constant quality mode.
forced-idr
Normally, when forcing a I-frame type, the encoder can select any
type of I-frame. This option forces it to choose an IDR-frame.
x265-params
Set x265 options using a list of key=value couples separated by
":". See x265 --help for a list of options.
For example to specify libx265 encoding options with -x265-params:
ffmpeg -i input -c:v libx265 -x265-params crf=26:psy-rd=1 output.mp4
libxvid
Xvid MPEG-4 Part 2 encoder wrapper.
This encoder requires the presence of the libxvidcore headers and
library during configuration. You need to explicitly configure the
build with "--enable-libxvid --enable-gpl".
The native "mpeg4" encoder supports the MPEG-4 Part 2 format, so users
can encode to this format without this library.
Options
The following options are supported by the libxvid wrapper. Some of the
following options are listed but are not documented, and correspond to
shared codec options. See the Codec Options chapter for their
documentation. The other shared options which are not listed have no
effect for the libxvid encoder.
b
g
qmin
qmax
mpeg_quant
threads
bf
b_qfactor
b_qoffset
flags
Set specific encoding flags. Possible values:
mv4 Use four motion vector by macroblock.
aic Enable high quality AC prediction.
gray
Only encode grayscale.
gmc Enable the use of global motion compensation (GMC).
qpel
Enable quarter-pixel motion compensation.
cgop
Enable closed GOP.
global_header
Place global headers in extradata instead of every keyframe.
trellis
me_method
Set motion estimation method. Possible values in decreasing order
of speed and increasing order of quality:
zero
Use no motion estimation (default).
phods
x1
log Enable advanced diamond zonal search for 16x16 blocks and half-
pixel refinement for 16x16 blocks. x1 and log are aliases for
phods.
epzs
Enable all of the things described above, plus advanced diamond
zonal search for 8x8 blocks, half-pixel refinement for 8x8
blocks, and motion estimation on chroma planes.
full
Enable all of the things described above, plus extended 16x16
and 8x8 blocks search.
mbd Set macroblock decision algorithm. Possible values in the
increasing order of quality:
simple
Use macroblock comparing function algorithm (default).
bits
Enable rate distortion-based half pixel and quarter pixel
refinement for 16x16 blocks.
rd Enable all of the things described above, plus rate distortion-
based half pixel and quarter pixel refinement for 8x8 blocks,
and rate distortion-based search using square pattern.
lumi_aq
Enable lumi masking adaptive quantization when set to 1. Default is
0 (disabled).
variance_aq
Enable variance adaptive quantization when set to 1. Default is 0
(disabled).
When combined with lumi_aq, the resulting quality will not be
better than any of the two specified individually. In other words,
the resulting quality will be the worse one of the two effects.
ssim
Set structural similarity (SSIM) displaying method. Possible
values:
off Disable displaying of SSIM information.
avg Output average SSIM at the end of encoding to stdout. The
format of showing the average SSIM is:
Average SSIM: %f
For users who are not familiar with C, %f means a float number,
or a decimal (e.g. 0.939232).
frame
Output both per-frame SSIM data during encoding and average
SSIM at the end of encoding to stdout. The format of per-frame
information is:
SSIM: avg: %1.3f min: %1.3f max: %1.3f
For users who are not familiar with C, %1.3f means a float
number rounded to 3 digits after the dot (e.g. 0.932).
ssim_acc
Set SSIM accuracy. Valid options are integers within the range of
0-4, while 0 gives the most accurate result and 4 computes the
fastest.
mpeg2
MPEG-2 video encoder.
Options
seq_disp_ext integer
Specifies if the encoder should write a sequence_display_extension
to the output.
-1
auto
Decide automatically to write it or not (this is the default)
by checking if the data to be written is different from the
default or unspecified values.
0
never
Never write it.
1
always
Always write it.
video_format integer
Specifies the video_format written into the sequence display
extension indicating the source of the video pictures. The default
is unspecified, can be component, pal, ntsc, secam or mac. For
maximum compatibility, use component.
png
PNG image encoder.
Private options
dpi integer
Set physical density of pixels, in dots per inch, unset by default
dpm integer
Set physical density of pixels, in dots per meter, unset by default
ProRes
Apple ProRes encoder.
FFmpeg contains 2 ProRes encoders, the prores-aw and prores-ks encoder.
The used encoder can be chosen with the "-vcodec" option.
Private Options for prores-ks
profile integer
Select the ProRes profile to encode
proxy
lt
standard
hq
4444
4444xq
quant_mat integer
Select quantization matrix.
auto
default
proxy
lt
standard
hq
If set to auto, the matrix matching the profile will be picked. If
not set, the matrix providing the highest quality, default, will be
picked.
bits_per_mb integer
How many bits to allot for coding one macroblock. Different
profiles use between 200 and 2400 bits per macroblock, the maximum
is 8000.
mbs_per_slice integer
Number of macroblocks in each slice (1-8); the default value (8)
should be good in almost all situations.
vendor string
Override the 4-byte vendor ID. A custom vendor ID like apl0 would
claim the stream was produced by the Apple encoder.
alpha_bits integer
Specify number of bits for alpha component. Possible values are 0,
8 and 16. Use 0 to disable alpha plane coding.
Speed considerations
In the default mode of operation the encoder has to honor frame
constraints (i.e. not produce frames with size bigger than requested)
while still making output picture as good as possible. A frame
containing a lot of small details is harder to compress and the encoder
would spend more time searching for appropriate quantizers for each
slice.
Setting a higher bits_per_mb limit will improve the speed.
For the fastest encoding speed set the qscale parameter (4 is the
recommended value) and do not set a size constraint.
QSV encoders
The family of Intel QuickSync Video encoders (MPEG-2, H.264 and HEVC)
The ratecontrol method is selected as follows:
o When global_quality is specified, a quality-based mode is used.
Specifically this means either
- CQP - constant quantizer scale, when the qscale codec flag is
also set (the -qscale ffmpeg option).
- LA_ICQ - intelligent constant quality with lookahead, when the
look_ahead option is also set.
- ICQ -- intelligent constant quality otherwise.
o Otherwise, a bitrate-based mode is used. For all of those, you
should specify at least the desired average bitrate with the b
option.
- LA - VBR with lookahead, when the look_ahead option is
specified.
- VCM - video conferencing mode, when the vcm option is set.
- CBR - constant bitrate, when maxrate is specified and equal to
the average bitrate.
- VBR - variable bitrate, when maxrate is specified, but is
higher than the average bitrate.
- AVBR - average VBR mode, when maxrate is not specified. This
mode is further configured by the avbr_accuracy and
avbr_convergence options.
Note that depending on your system, a different mode than the one you
specified may be selected by the encoder. Set the verbosity level to
verbose or higher to see the actual settings used by the QSV runtime.
Additional libavcodec global options are mapped to MSDK options as
follows:
o g/gop_size -> GopPicSize
o bf/max_b_frames+1 -> GopRefDist
o rc_init_occupancy/rc_initial_buffer_occupancy -> InitialDelayInKB
o slices -> NumSlice
o refs -> NumRefFrame
o b_strategy/b_frame_strategy -> BRefType
o cgop/CLOSED_GOP codec flag -> GopOptFlag
o For the CQP mode, the i_qfactor/i_qoffset and b_qfactor/b_qoffset
set the difference between QPP and QPI, and QPP and QPB
respectively.
o Setting the coder option to the value vlc will make the H.264
encoder use CAVLC instead of CABAC.
snow
Options
iterative_dia_size
dia size for the iterative motion estimation
VAAPI encoders
Wrappers for hardware encoders accessible via VAAPI.
These encoders only accept input in VAAPI hardware surfaces. If you
have input in software frames, use the hwupload filter to upload them
to the GPU.
The following standard libavcodec options are used:
o g / gop_size
o bf / max_b_frames
o profile
If not set, this will be determined automatically from the format
of the input frames and the profiles supported by the driver.
o level
o b / bit_rate
o maxrate / rc_max_rate
o bufsize / rc_buffer_size
o rc_init_occupancy / rc_initial_buffer_occupancy
o compression_level
Speed / quality tradeoff: higher values are faster / worse quality.
o q / global_quality
Size / quality tradeoff: higher values are smaller / worse quality.
o qmin
o qmax
o i_qfactor / i_quant_factor
o i_qoffset / i_quant_offset
o b_qfactor / b_quant_factor
o b_qoffset / b_quant_offset
o slices
All encoders support the following options:
o low_power
Some drivers/platforms offer a second encoder for some codecs
intended to use less power than the default encoder; setting this
option will attempt to use that encoder. Note that it may support
a reduced feature set, so some other options may not be available
in this mode.
Each encoder also has its own specific options:
h264_vaapi
profile sets the value of profile_idc and the
constraint_set*_flags. level sets the value of level_idc.
coder
Set entropy encoder (default is cabac). Possible values:
ac
cabac
Use CABAC.
vlc
cavlc
Use CAVLC.
aud Include access unit delimiters in the stream (not included by
default).
sei Set SEI message types to include. Some combination of the
following values:
identifier
Include a user_data_unregistered message containing
information about the encoder.
timing
Include picture timing parameters (buffering_period and
pic_timing messages).
recovery_point
Include recovery points where appropriate (recovery_point
messages).
hevc_vaapi
profile and level set the values of general_profile_idc and
general_level_idc respectively.
aud Include access unit delimiters in the stream (not included by
default).
tier
Set general_tier_flag. This may affect the level chosen for
the stream if it is not explicitly specified.
sei Set SEI message types to include. Some combination of the
following values:
hdr Include HDR metadata if the input frames have it
(mastering_display_colour_volume and content_light_level
messages).
mjpeg_vaapi
Only baseline DCT encoding is supported. The encoder always uses
the standard quantisation and huffman tables - global_quality
scales the standard quantisation table (range 1-100).
For YUV, 4:2:0, 4:2:2 and 4:4:4 subsampling modes are supported.
RGB is also supported, and will create an RGB JPEG.
jfif
Include JFIF header in each frame (not included by default).
huffman
Include standard huffman tables (on by default). Turning this
off will save a few hundred bytes in each output frame, but may
lose compatibility with some JPEG decoders which don't fully
handle MJPEG.
mpeg2_vaapi
profile and level set the value of profile_and_level_indication.
vp8_vaapi
B-frames are not supported.
global_quality sets the q_idx used for non-key frames (range
0-127).
loop_filter_level
loop_filter_sharpness
Manually set the loop filter parameters.
vp9_vaapi
global_quality sets the q_idx used for P-frames (range 0-255).
loop_filter_level
loop_filter_sharpness
Manually set the loop filter parameters.
B-frames are supported, but the output stream is always in encode
order rather than display order. If B-frames are enabled, it may
be necessary to use the vp9_raw_reorder bitstream filter to modify
the output stream to display frames in the correct order.
Only normal frames are produced - the vp9_superframe bitstream
filter may be required to produce a stream usable with all
decoders.
vc2
SMPTE VC-2 (previously BBC Dirac Pro). This codec was primarily aimed
at professional broadcasting but since it supports yuv420, yuv422 and
yuv444 at 8 (limited range or full range), 10 or 12 bits, this makes it
suitable for other tasks which require low overhead and low compression
(like screen recording).
Options
b Sets target video bitrate. Usually that's around 1:6 of the
uncompressed video bitrate (e.g. for 1920x1080 50fps yuv422p10
that's around 400Mbps). Higher values (close to the uncompressed
bitrate) turn on lossless compression mode.
field_order
Enables field coding when set (e.g. to tt - top field first) for
interlaced inputs. Should increase compression with interlaced
content as it splits the fields and encodes each separately.
wavelet_depth
Sets the total amount of wavelet transforms to apply, between 1 and
5 (default). Lower values reduce compression and quality. Less
capable decoders may not be able to handle values of wavelet_depth
over 3.
wavelet_type
Sets the transform type. Currently only 5_3 (LeGall) and 9_7
(Deslauriers-Dubuc) are implemented, with 9_7 being the one with
better compression and thus is the default.
slice_width
slice_height
Sets the slice size for each slice. Larger values result in better
compression. For compatibility with other more limited decoders
use slice_width of 32 and slice_height of 8.
tolerance
Sets the undershoot tolerance of the rate control system in
percent. This is to prevent an expensive search from being run.
qm Sets the quantization matrix preset to use by default or when
wavelet_depth is set to 5
- default Uses the default quantization matrix from the
specifications, extended with values for the fifth level. This
provides a good balance between keeping detail and omitting
artifacts.
- flat Use a completely zeroed out quantization matrix. This
increases PSNR but might reduce perception. Use in bogus
benchmarks.
- color Reduces detail but attempts to preserve color at
extremely low bitrates.
libxavs2
xavs2 AVS2-P2/IEEE1857.4 encoder wrapper.
This encoder requires the presence of the libxavs2 headers and library
during configuration. You need to explicitly configure the build with
--enable-libxavs2.
Options
lcu_row_threads
Set the number of parallel threads for rows from 1 to 8 (default
5).
initial_qp
Set the xavs2 quantization parameter from 1 to 63 (default 34).
This is used to set the initial qp for the first frame.
qp Set the xavs2 quantization parameter from 1 to 63 (default 34).
This is used to set the qp value under constant-QP mode.
max_qp
Set the max qp for rate control from 1 to 63 (default 55).
min_qp
Set the min qp for rate control from 1 to 63 (default 20).
speed_level
Set the Speed level from 0 to 9 (default 0). Higher is better but
slower.
log_level
Set the log level from -1 to 3 (default 0). -1: none, 0: error, 1:
warning, 2: info, 3: debug.
xavs2-params
Set xavs2 options using a list of key=value couples separated by
":".
For example to specify libxavs2 encoding options with
-xavs2-params:
ffmpeg -i input -c:v libxavs2 -xavs2-params preset_level=5 output.avs2
SUBTITLES ENCODERS
dvdsub
This codec encodes the bitmap subtitle format that is used in DVDs.
Typically they are stored in VOBSUB file pairs (*.idx + *.sub), and
they can also be used in Matroska files.
Options
even_rows_fix
When set to 1, enable a work-around that makes the number of pixel
rows even in all subtitles. This fixes a problem with some players
that cut off the bottom row if the number is odd. The work-around
just adds a fully transparent row if needed. The overhead is low,
typically one byte per subtitle on average.
By default, this work-around is disabled.
SEE ALSO
ffmpeg(1), ffplay(1), ffprobe(1), libavcodec(3)
AUTHORS
The FFmpeg developers.
For details about the authorship, see the Git history of the project
(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command git log in
the FFmpeg source directory, or browsing the online repository at
<http://source.ffmpeg.org>.
Maintainers for the specific components are listed in the file
MAINTAINERS in the source code tree.
ffmpeg-codecs(1)
ffmpeg 4.1 - Generated Thu Nov 8 18:44:02 CST 2018