flac(1) Free Lossless Audio Codec conversion tool flac(1)
NAME
flac - Free Lossless Audio Codec
SYNOPSIS
flac [ OPTIONS ] [ infile.wav | infile.rf64 | infile.aiff | infile.raw |
infile.flac | infile.oga | infile.ogg | - ... ]
flac [ -d | --decode | -t | --test | -a | --analyze ] [ OPTIONS ] [
infile.flac | infile.oga | infile.ogg | - ... ]
DESCRIPTION
flac is a command-line tool for encoding, decoding, testing and analyzing
FLAC streams.
GENERAL USAGE
flac supports as input RIFF WAVE, Wave64, RF64, AIFF, FLAC or Ogg FLAC
format, or raw interleaved samples. The decoder currently can output to
RIFF WAVE, Wave64, RF64, or AIFF format, or raw interleaved samples.
flac only supports linear PCM samples (in other words, no A-LAW, uLAW,
etc.), and the input must be between 4 and 32 bits per sample.
flac assumes that files ending in ".wav" or that have the RIFF WAVE
header present are WAVE files, files ending in ".w64" or have the Wave64
header present are Wave64 files, files ending in ".rf64" or have the RF64
header present are RF64 files, files ending in ".aif" or ".aiff" or have
the AIFF header present are AIFF files, files ending in ".flac" or have
the FLAC header present are FLAC files and files ending in ".oga" or
".ogg" or have the Ogg FLAC header present are Ogg FLAC files.
Other than this, flac makes no assumptions about file extensions, though
the convention is that FLAC files have the extension ".flac" (or ".fla"
on ancient "8.3" file systems like FAT-16).
Before going into the full command-line description, a few other things
help to sort it out: 1. flac encodes by default, so you must use -d to
decode 2. the options -0 .. -8 (or -fast and -best) that control the
compression level actually are just synonyms for different groups of
specific encoding options (described later) and you can get the same
effect by using the same options. When specific options are specified
they take priority over the compression level no matter the order 3.
flac behaves similarly to gzip in the way it handles input and output
files 4. the order in which options are specified is generally not
important
Skip to the examples below for examples of some common tasks.
flac will be invoked one of four ways, depending on whether you are
encoding, decoding, testing, or analyzing. Encoding is the default
invocation, but can be switch to decoding with -d, analysis with -a or
testing with -t. Depending on which way is chosen, encoding, decoding,
analysis or testing options can be used, see section OPTIONS for details.
General options can be used for all.
If only one inputfile is specified, it may be "-" for stdin. When stdin
is used as input, flac will write to stdout. Otherwise flac will perform
the desired operation on each input file to similarly named output files
(meaning for encoding, the extension will be replaced with ".flac", or
appended with ".flac" if the input file has no extension, and for
decoding, the extension will be ".wav" for WAVE output and ".raw" for raw
output). The original file is not deleted unless -delete-input-file is
specified.
If you are encoding/decoding from stdin to a file, you should use the -o
option like so:
flac [options] -o outputfile
flac -d [options] -o outputfile
which are better than:
flac [options] > outputfile
flac -d [options] > outputfile
since the former allows flac to seek backwards to write the STREAMINFO or
RIFF WAVE header contents when necessary.
Also, you can force output data to go to stdout using -c.
To encode or decode files that start with a dash, use - to signal the end
of options, to keep the filenames themselves from being treated as
options:
flac -V -- -01-filename.wav
The encoding options affect the compression ratio and encoding speed.
The format options are used to tell flac the arrangement of samples if
the input file (or output file when decoding) is a raw file. If it is a
RIFF WAVE, Wave64, RF64, or AIFF file the format options are not needed
since they are read from the file's header.
In test mode, flac acts just like in decode mode, except no output file
is written. Both decode and test modes detect errors in the stream, but
they also detect when the MD5 signature of the decoded audio does not
match the stored MD5 signature, even when the bitstream is valid.
flac can also re-encode FLAC files. In other words, you can specify a
FLAC or Ogg FLAC file as an input to the encoder and it will decoder it
and re-encode it according to the options you specify. It will also
preserve all the metadata unless you override it with other options (e.g.
specifying new tags, seekpoints, cuesheet, padding, etc.).
flac has been tuned so that the default settings yield a good speed vs.
compression tradeoff for many kinds of input. However, if you are
looking to maximize the compression rate or speed, or want to use the
full power of FLAC's metadata system, see the page titled `About the FLAC
Format' on the FLAC website.
EXAMPLES
Some common encoding tasks using flac:
flac abc.wav
Encode abc.wav to abc.flac using the default compression setting.
abc.wav is not deleted.
flac --delete-input-file abc.wav
Like above, except abc.wav is deleted if there were no errors.
flac --delete-input-file -w abc.wav
Like above, except abc.wav is deleted if there were no errors or
warnings.
flac --best abc.wav
Encode abc.wav to abc.flac using the highest compression setting.
flac --verify abc.wav
Encode abc.wav to abc.flac and internally decode abc.flac to make
sure it matches abc.wav.
flac -o my.flac abc.wav
Encode abc.wav to my.flac.
flac -T "TITLE=Bohemian Rhapsody" -T "ARTIST=Queen" abc.wav
Encode abc.wav and add some tags at the same time to abc.flac.
flac *.wav
Encode all .wav files in the current directory.
flac abc.aiff
Encode abc.aiff to abc.flac.
flac abc.rf64
Encode abc.rf64 to abc.flac.
flac abc.w64
Encode abc.w64 to abc.flac.
flac abc.flac --force
This one's a little tricky: notice that flac is in encode mode by
default (you have to specify -d to decode) so this command
actually recompresses abc.flac back to abc.flac. -force is needed
to make sure you really want to overwrite abc.flac with a new
version. Why would you want to do this? It allows you to
recompress an existing FLAC file with (usually) higher compression
options or a newer version of FLAC and preserve all the metadata
like tags too.
Some common decoding tasks using flac:
flac -d abc.flac
Decode abc.flac to abc.wav. abc.flac is not deleted. NOTE:
Without -d it means re-encode abc.flac to abc.flac (see above).
flac -d --force-aiff-format abc.flac
flac -d -o abc.aiff abc.flac : Two different ways of decoding abc.flac to
abc.aiff (AIFF format). abc.flac is not deleted.
flac -d --force-rf64-format abc.flac
flac -d -o abc.rf64 abc.flac : Two different ways of decoding abc.flac to
abc.rf64 (RF64 format). abc.flac is not deleted.
flac -d --force-wave64-format abc.flac
flac -d -o abc.w64 abc.flac : Two different ways of decoding abc.flac to
abc.w64 (Wave64 format). abc.flac is not deleted.
flac -d -F abc.flac
Decode abc.flac to abc.wav and don't abort if errors are found
(useful for recovering as much as possible from corrupted files).
OPTIONS
A summary of options is included below. For a complete description, see
the HTML documentation.
GENERAL OPTIONS
-v, --version
Show the flac version number
-h, --help
Show basic usage and a list of all options
-H, --explain
Show detailed explanation of usage and all options
-d, --decode
Decode (the default behavior is to encode)
-t, --test
Test a flac encoded file (same as -d except no decoded file is
written)
-a, --analyze
Analyze a FLAC encoded file (same as -d except an analysis file is
written)
-c, --stdout
Write output to stdout
-s, --silent
Silent mode (do not write runtime encode/decode statistics to
stderr)
--totally-silent
Do not print anything of any kind, including warnings or errors.
The exit code will be the only way to determine successful
completion.
--no-utf8-convert
Do not convert tags from local charset to UTF-8. This is useful
for scripts, and setting tags in situations where the locale is
wrong. This option must appear before any tag options!
-w, --warnings-as-errors
Treat all warnings as errors (which cause flac to terminate with a
non-zero exit code).
-f, --force
Force overwriting of output files. By default, flac warns that
the output file already exists and continues to the next file.
-o filename, --output-name=filename
Force the output file name (usually flac just changes the
extension). May only be used when encoding a single file. May
not be used in conjunction with --output-prefix.
--output-prefix=string
Prefix each output file name with the given string. This can be
useful for encoding or decoding files to a different directory.
Make sure if your string is a path name that it ends with a
trailing `/' (slash).
--delete-input-file
Automatically delete the input file after a successful encode or
decode. If there was an error (including a verify error) the
input file is left intact.
--preserve-modtime
Output files have their timestamps/permissions set to match those
of their inputs (this is default). Use --no-preserve-modtime to
make output files have the current time and default permissions.
--keep-foreign-metadata
If encoding, save WAVE, RF64, or AIFF non-audio chunks in FLAC
metadata. If decoding, restore any saved non-audio chunks from
FLAC metadata when writing the decoded file. Foreign metadata
cannot be transcoded, e.g. WAVE chunks saved in a FLAC file cannot
be restored when decoding to AIFF. Input and output must be
regular files (not stdin or stdout).
--keep-foreign-metadata-if-present
Like --keep-foreign-metadata, but without throwing an error if
foreign metadata cannot be found or restored, instead printing a
warning.
--skip={#|mm:ss.ss}
Skip over the first number of samples of the input. This works
for both encoding and decoding, but not testing. The alternative
form mm:ss.ss can be used to specify minutes, seconds, and
fractions of a second.
--until={#|[+|-]mm:ss.ss}
Stop at the given sample number for each input file. This works
for both encoding and decoding, but not testing. The given sample
number is not included in the decoded output. The alternative
form mm:ss.ss can be used to specify minutes, seconds, and
fractions of a second. If a `+' (plus) sign is at the beginning,
the --until point is relative to the --skip point. If a `-'
(minus) sign is at the beginning, the --until point is relative to
end of the audio.
--ogg When encoding, generate Ogg FLAC output instead of native FLAC.
Ogg FLAC streams are FLAC streams wrapped in an Ogg transport
layer. The resulting file should have an `.oga' extension and
will still be decodable by flac. When decoding, force the input
to be treated as Ogg FLAC. This is useful when piping input from
stdin or when the filename does not end in `.oga' or `.ogg'.
--serial-number=#
When used with --ogg, specifies the serial number to use for the
first Ogg FLAC stream, which is then incremented for each
additional stream. When encoding and no serial number is given,
flac uses a random number for the first stream, then increments it
for each additional stream. When decoding and no number is given,
flac uses the serial number of the first page.
ANALYSIS OPTIONS
--residual-text
Includes the residual signal in the analysis file. This will make
the file very big, much larger than even the decoded file.
--residual-gnuplot
Generates a gnuplot file for every subframe; each file will
contain the residual distribution of the subframe. This will
create a lot of files.
DECODING OPTIONS
--cue=[#.#][-[#.#]]
Set the beginning and ending cuepoints to decode. The optional
first #.# is the track and index point at which decoding will
start; the default is the beginning of the stream. The optional
second #.# is the track and index point at which decoding will
end; the default is the end of the stream. If the cuepoint does
not exist, the closest one before it (for the start point) or
after it (for the end point) will be used. If those don't exist,
the start of the stream (for the start point) or end of the stream
(for the end point) will be used. The cuepoints are merely
translated into sample numbers then used as --skip and --until. A
CD track can always be cued by, for example, --cue=9.1-10.1 for
track 9, even if the CD has no 10th track.
-F, --decode-through-errors
By default flac stops decoding with an error and removes the
partially decoded file if it encounters a bitstream error. With
-F, errors are still printed but flac will continue decoding to
completion. Note that errors may cause the decoded audio to be
missing some samples or have silent sections.
--apply-replaygain-which-is-not-lossless[=<specification>]
Applies ReplayGain values while decoding. WARNING: THIS IS NOT
LOSSLESS. DECODED AUDIO WILL NOT BE IDENTICAL TO THE ORIGINAL
WITH THIS OPTION. This option is useful for example in transcoding
media servers, where the client does not support ReplayGain. For
details on the use of this option, see the section ReplayGain
application specification.
ENCODING OPTIONS
-V, --verify
Verify a correct encoding by decoding the output in parallel and
comparing to the original
--lax Allow encoder to generate non-Subset files. The resulting FLAC
file may not be streamable or might have trouble being played in
all players (especially hardware devices), so you should only use
this option in combination with custom encoding options meant for
archival.
--replay-gain
Calculate ReplayGain values and store them as FLAC tags, similar
to vorbisgain. Title gains/peaks will be computed for each input
file, and an album gain/peak will be computed for all files. All
input files must have the same resolution, sample rate, and number
of channels. Only mono and stereo files are allowed, and the
sample rate must be one of 8, 11.025, 12, 16, 22.05, 24, 32, 44.1,
or 48 kHz. Also note that this option may leave a few extra bytes
in a PADDING block as the exact size of the tags is not known
until all files are processed. Note that this option cannot be
used when encoding to standard output (stdout).
--cuesheet=filename
Import the given cuesheet file and store it in a CUESHEET metadata
block. This option may only be used when encoding a single file.
A seekpoint will be added for each index point in the cuesheet to
the SEEKTABLE unless --no-cued-seekpoints is specified.
--picture={FILENAME|SPECIFICATION}
Import a picture and store it in a PICTURE metadata block. More
than one --picture option can be specified. Either a filename for
the picture file or a more complete specification form can be
used. The SPECIFICATION is a string whose parts are separated by
| (pipe) characters. Some parts may be left empty to invoke
default values. FILENAME is just shorthand for "||||FILENAME".
For the format of SPECIFICATION, see the section picture
specification.
--sector-align
Align encoding of multiple CD format files on sector boundaries.
See the HTML documentation for more information. This option is
DEPRECATED and may not exist in future versions of flac.
--ignore-chunk-sizes
When encoding to flac, ignore the file size headers in WAV and
AIFF files to attempt to work around problems with over-sized or
malformed files. WAV and AIFF files both have an unsigned 32 bit
numbers in the file header which specifes the length of audio
data. Since this number is unsigned 32 bits, that limits the size
of a valid file to being just over 4 Gigabytes. Files larger than
this are mal-formed, but should be read correctly using this
option.
-S {#|X|#x|#s}, --seekpoint={#|X|#x|#s}
Include a point or points in a SEEKTABLE. Using #, a seek point
at that sample number is added. Using X, a placeholder point is
added at the end of a the table. Using #x, # evenly spaced seek
points will be added, the first being at sample 0. Using #s, a
seekpoint will be added every # seconds (# does not have to be a
whole number; it can be, for example, 9.5, meaning a seekpoint
every 9.5 seconds). You may use many -S options; the resulting
SEEKTABLE will be the unique-ified union of all such values. With
no -S options, flac defaults to `-S 10s'. Use --no-seektable for
no SEEKTABLE. Note: `-S #x' and `-S #s' will not work if the
encoder can't determine the input size before starting. Note: if
you use `-S #' and # is >= samples in the input, there will be
either no seek point entered (if the input size is determinable
before encoding starts) or a placeholder point (if input size is
not determinable).
-P #, --padding=#
Tell the encoder to write a PADDING metadata block of the given
length (in bytes) after the STREAMINFO block. This is useful if
you plan to tag the file later with an APPLICATION block; instead
of having to rewrite the entire file later just to insert your
block, you can write directly over the PADDING block. Note that
the total length of the PADDING block will be 4 bytes longer than
the length given because of the 4 metadata block header bytes.
You can force no PADDING block at all to be written with --no-
padding. The encoder writes a PADDING block of 8192 bytes by
default (or 65536 bytes if the input audio stream is more that 20
minutes long).
-T FIELD=VALUE, --tag=FIELD=VALUE
Add a FLAC tag. The comment must adhere to the Vorbis comment
spec; i.e. the FIELD must contain only legal characters,
terminated by an `equals' sign. Make sure to quote the comment if
necessary. This option may appear more than once to add several
comments. NOTE: all tags will be added to all encoded files.
--tag-from-file=FIELD=FILENAME
Like --tag, except FILENAME is a file whose contents will be read
verbatim to set the tag value. The contents will be converted to
UTF-8 from the local charset. This can be used to store a
cuesheet in a tag (e.g. --tag-from-file="CUESHEET=image.cue"). Do
not try to store binary data in tag fields! Use APPLICATION
blocks for that.
-b #, --blocksize=#
Specify the blocksize in samples. The default is 1152 for -l 0,
else 4096. For subset streams this must be <= 4608 if the
samplerate <= 48kHz, for subset streams with higher samplerates it
must be <= 16384.
-m, --mid-side
Try mid-side coding for each frame (stereo input only)
-M, --adaptive-mid-side
Adaptive mid-side coding for all frames (stereo input only)
-0..-8, --compression-level-0..--compression-level-8
Fastest compression..highest compression (default is -5). These
are synonyms for other options:
-0, --compression-level-0
Synonymous with -l 0 -b 1152 -r 3 --no-mid-side
-1, --compression-level-1
Synonymous with -l 0 -b 1152 -M -r 3
-2, --compression-level-2
Synonymous with -l 0 -b 1152 -m -r 3
-3, --compression-level-3
Synonymous with -l 6 -b 4096 -r 4 --no-mid-side
-4, --compression-level-4
Synonymous with -l 8 -b 4096 -M -r 4
-5, --compression-level-5
Synonymous with -l 8 -b 4096 -m -r 5
-6, --compression-level-6
Synonymous with -l 8 -b 4096 -m -r 6 -A subdivide_tukey(2)
-7, --compression-level-7
Synonymous with -l 12 -b 4096 -m -r 6 -A subdivide_tukey(2)
-8, --compression-level-8
Synonymous with -l 12 -b 4096 -m -r 6 -A subdivide_tukey(3)
--fast Fastest compression. Currently synonymous with -0.
--best Highest compression. Currently synonymous with -8.
-e, --exhaustive-model-search
Do exhaustive model search (expensive!)
-A function, --apodization=function
Window audio data with given the apodization function. See
section Apodization functions for details.
-l #, --max-lpc-order=#
Specifies the maximum LPC order. This number must be <= 32. For
subset streams, it must be <=12 if the sample rate is <=48kHz. If
0, the encoder will not attempt generic linear prediction, and use
only fixed predictors. Using fixed predictors is faster but
usually results in files being 5-10% larger.
-p, --qlp-coeff-precision-search
Do exhaustive search of LP coefficient quantization (expensive!).
Overrides -q; does nothing if using -l 0
-q #, --qlp-coeff-precision=#
Precision of the quantized linear-predictor coefficients, 0 => let
encoder decide (min is 5, default is 0)
-r [#,]#, --rice-partition-order=[#,]#
Set the [min,]max residual partition order (0..15). min defaults
to 0 if unspecified. Default is -r 5.
FORMAT OPTIONS
--endian={big|little}
Set the byte order for samples
--channels=#
Set number of channels.
--bps=#
Set bits per sample.
--sample-rate=#
Set sample rate (in Hz).
--sign={signed|unsigned}
Set the sign of samples (the default is signed).
--input-size=#
Specify the size of the raw input in bytes. If you are encoding
raw samples from stdin, you must set this option in order to be
able to use --skip, --until, --cuesheet, or other options that
need to know the size of the input beforehand. If the size given
is greater than what is found in the input stream, the encoder
will complain about an unexpected end-of-file. If the size given
is less, samples will be truncated.
--force-raw-format
Force input (when encoding) or output (when decoding) to be
treated as raw samples (even if filename ends in .wav).
--force-aiff-format
Force the decoder to output AIFF format. This option is not
needed if the output filename (as set by -o) ends with .aif or
.aiff. Also, this option has no effect when encoding since input
AIFF is auto-detected.
--force-rf64-format
Force the decoder to output RF64 format. This option is not
needed if the output filename (as set by -o) ends with .rf64.
Also, this option has no effect when encoding since input RF64 is
auto-detected.
--force-wave64-format
Force the decoder to output Wave64 format. This option is not
needed if the output filename (as set by -o) ends with .w64.
Also, this option has no effect when encoding since input Wave64
is auto-detected.
NEGATIVE OPTIONS
--no-adaptive-mid-side
--no-cued-seekpoints
--no-decode-through-errors
--no-delete-input-file
--no-preserve-modtime
--no-keep-foreign-metadata
--no-exhaustive-model-search
--no-force
--no-lax
--no-mid-side
--no-ogg
--no-padding
--no-qlp-coeff-prec-search
--no-replay-gain
--no-residual-gnuplot
--no-residual-text
--no-sector-align
--no-seektable
--no-silent
--no-verify
--no-warnings-as-errors
These flags can be used to invert the sense of the corresponding normal
option.
ReplayGain application specification
The option --apply-replaygain-which-is-not-lossless[=<specification>]
applies ReplayGain values while decoding. WARNING: THIS IS NOT LOSSLESS.
DECODED AUDIO WILL NOT BE IDENTICAL TO THE ORIGINAL WITH THIS OPTION.**
This option is useful for example in transcoding media servers, where the
client does not support ReplayGain.
The equals sign and <specification> is optional. If omitted, the default
specification is 0aLn1.
The <specification> is a shorthand notation for describing how to apply
ReplayGain. All components are optional but order is important. `[]'
means `optional'. `|' means `or'. `{}' means required. The format is:
[<preamp>][a|t][l|L][n{0|1|2|3}]
In which the following parameters are used:
o preamp: A floating point number in dB. This is added to the existing
gain value.
o a|t: Specify `a' to use the album gain, or `t' to use the track gain.
If tags for the preferred kind (album/track) do not exist but tags for
the other (track/album) do, those will be used instead.
o l|L: Specify `l' to peak-limit the output, so that the ReplayGain peak
value is full-scale. Specify `L' to use a 6dB hard limiter that kicks
in when the signal approaches full-scale.
o n{0|1|2|3}: Specify the amount of noise shaping. ReplayGain synthesis
happens in floating point; the result is dithered before converting
back to integer. This quantization adds noise. Noise shaping tries to
move the noise where you won't hear it as much. 0 means no noise
shaping, 1 means `low', 2 means `medium', 3 means `high'.
For example, the default of 0aLn1 means 0dB preamp, use album gain, 6dB
hard limit, low noise shaping. --apply-replaygain-which-is-not-
lossless=3 means 3dB preamp, use album gain, no limiting, no noise
shaping.
flac uses the ReplayGain tags for the calculation. If a stream does not
have the required tags or they can't be parsed, decoding will continue
with a warning, and no ReplayGain is applied to that stream.
Picture specification
This described the specification used for the --picture option.
[TYPE]|[MIME-TYPE]|[DESCRIPTION]|[WIDTHxHEIGHTxDEPTH[/COLORS]]|FILE
TYPE is optional; it is a number from one of:
0. Other
1. 32x32 pixels `file icon' (PNG only)
2. Other file icon
3. Cover (front)
4. Cover (back)
5. Leaflet page
6. Media (e.g. label side of CD)
7. Lead artist/lead performer/soloist
8. Artist/performer
9. Conductor
10. Band/Orchestra
11. Composer
12. Lyricist/text writer
13. Recording Location
14. During recording
15. During performance
16. Movie/video screen capture
17. A bright coloured fish
18. Illustration
19. Band/artist logotype
20. Publisher/Studio logotype
The default is 3 (front cover). There may only be one picture each of
type 1 and 2 in a file.
MIME-TYPE is optional; if left blank, it will be detected from the file.
For best compatibility with players, use pictures with MIME type
image/jpeg or image/png. The MIME type can also be --> to mean that FILE
is actually a URL to an image, though this use is discouraged.
DESCRIPTION is optional; the default is an empty string.
The next part specifies the resolution and color information. If the
MIME-TYPE is image/jpeg, image/png, or image/gif, you can usually leave
this empty and they can be detected from the file. Otherwise, you must
specify the width in pixels, height in pixels, and color depth in bits-
per-pixel. If the image has indexed colors you should also specify the
number of colors used. When manually specified, it is not checked
against the file for accuracy.
FILE is the path to the picture file to be imported, or the URL if MIME
type is -->
For example, "|image/jpeg|||../cover.jpg" will embed the JPEG file at
../cover.jpg, defaulting to type 3 (front cover) and an empty
description. The resolution and color info will be retrieved from the
file itself.
The specification
"4|-->|CD|320x300x24/173|http://blah.blah/backcover.tiff" will embed the
given URL, with type 4 (back cover), description "CD", and a manually
specified resolution of 320x300, 24 bits-per-pixel, and 173 colors. The
file at the URL will not be fetched; the URL itself is stored in the
PICTURE metadata block.
Apodization functions
To improve LPC analysis, audio data is windowed . The window can be
selected with one or more -A options. Possible functions are: bartlett,
bartlett_hann, blackman, blackman_harris_4term_92db, connes, flattop,
gauss(STDDEV), hamming, hann, kaiser_bessel, nuttall, rectangle,
triangle, tukey(P), partial_tukey(n[/ov[/P]]),
punchout_tukey(n[/ov[/P]]), subdivide_tukey(n[/P]) welch.
o For gauss(STDDEV), STDDEV is the standard deviation (0<STDDEV<=0.5).
o For tukey(P), P specifies the fraction of the window that is tapered
(0<=P<=1; P=0 corresponds to "rectangle" and P=1 corresponds to
"hann").
o For partial_tukey(n) and punchout_tukey(n), n apodization functions are
added that span different parts of each block. Values of 2 to 6 seem
to yield sane results. If necessary, an overlap can be specified, as
can be the taper parameter, for example partial_tukey(2/0.2) or
partial_tukey(2/0.2/0.5). ov should be smaller than 1 and can be
negative. The use of this is that different parts of a block are
ignored as the might contain transients which are hard to predict
anyway. The encoder will try each different added apodization (each
covering a different part of the block) to see which resulting
predictor results in the smallest representation.
o subdivide_tukey(n) is a more efficient reimplementation of
partial_tukey and punchout_tukey taken together, recycling as much data
as possible. It combines all possible non-redundant partial_tukey(n)
and punchout_tukey(n) up to the n specified. Specifying
subdivide_tukey(3) is equivalent to specifying tukey, partial_tukey(2),
partial_tukey(3) and punchout_tukey(3), specifying subdivide_tukey(5)
equivalently adds partial_tukey(4), punchout_tukey(4), partial_tukey(5)
and punchout_tukey(5). To be able to reuse data as much as possible,
the tukey taper is taken equal for all windows, and the P specified is
applied for the smallest used window. In other words,
subdivide_tukey(2/0.5) results in a taper equal to that of tukey(0.25)
and subdivide_tukey(5) in a taper equal to that of tukey(0.1). The
default P for subdivide_tukey when none is specified is 0.5.
Note that P, STDDEV and ov are locale specific, so a comma as decimal
separator might be required instead of a dot. Use scientific notation
for a locale-independent specification, for example tukey(5e-1) instead
of tukey(0.5) or tukey(0,5).
More than one -A option (up to 32) may be used. Any function that is
specified erroneously is silently dropped. The encoder chooses suitable
defaults in the absence of any -A options; any -A option specified
replaces the default(s).
When more than one function is specified, then for every subframe the
encoder will try each of them separately and choose the window that
results in the smallest compressed subframe. Multiple functions can
greatly increase the encoding time.
SEE ALSO
flac(1)
AUTHOR
This manual page was initially written by Matt Zimmerman <mdz@debian.org>
for the Debian GNU/Linux system (but may be used by others). It has been
kept up-to-date by the Xiph.org Foundation.
Version 1.4.2 flac(1)
flac 1.4.2 - Generated Sat Jan 7 08:21:25 CST 2023