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GstAudioCdSrc

GstAudioCdSrc — Base class for Audio CD sources

Properties

gchar * device Read / Write
GstAudioCdSrcMode mode Read / Write
guint track Read / Write

Types and Values

Object Hierarchy

    GObject
    ╰── GInitiallyUnowned
        ╰── GstObject
            ╰── GstElement
                ╰── GstBaseSrc
                    ╰── GstPushSrc
                        ╰── GstAudioCdSrc

Implemented Interfaces

GstAudioCdSrc implements GstURIHandler.

Includes

#include <gst/audio/gstaudiocdsrc.h>

Description

Provides a base class for CD digital audio (CDDA) sources, which handles things like seeking, querying, discid calculation, tags, and buffer timestamping.

Using GstAudioCdSrc-based elements in applications

GstAudioCdSrc registers two GstFormats of its own, namely the "track" format and the "sector" format. Applications will usually only find the "track" format interesting. You can retrieve that GstFormat for use in seek events or queries with gst_format_get_by_nick("track").

In order to query the number of tracks, for example, an application would set the CDDA source element to READY or PAUSED state and then query the the number of tracks via gst_element_query_duration() using the track format acquired above. Applications can query the currently playing track in the same way.

Alternatively, applications may retrieve the currently playing track and the total number of tracks from the taglist that will posted on the bus whenever the CD is opened or the currently playing track changes. The taglist will contain GST_TAG_TRACK_NUMBER and GST_TAG_TRACK_COUNT tags.

Applications playing back CD audio using playbin and cdda://n URIs should issue a seek command in track format to change between tracks, rather than setting a new cdda://n+1 URI on playbin (as setting a new URI on playbin involves closing and re-opening the CD device, which is much much slower).

Tags and meta-information

CDDA sources will automatically emit a number of tags, details about which can be found in the libgsttag documentation. Those tags are: GST_TAG_CDDA_CDDB_DISCID, GST_TAG_CDDA_CDDB_DISCID_FULL, GST_TAG_CDDA_MUSICBRAINZ_DISCID, GST_TAG_CDDA_MUSICBRAINZ_DISCID_FULL, among others.

Tracks and Table of Contents (TOC)

Applications will be informed of the available tracks via a TOC message on the pipeline's GstBus. The GstToc will contain a GstTocEntry for each track, with information about each track. The duration for each track can be retrieved via the GST_TAG_DURATION tag from each entry's tag list, or calculated via gst_toc_entry_get_start_stop_times(). The track entries in the TOC will be sorted by track number.

Functions

gst_audio_cd_src_add_track ()

gboolean
gst_audio_cd_src_add_track (GstAudioCdSrc *src,
                            GstAudioCdSrcTrack *track);

CDDA sources use this function from their start vfunc to announce the available data and audio tracks to the base source class. The caller should allocate track on the stack, the base source will do a shallow copy of the structure (and take ownership of the taglist if there is one).

Parameters

src

a GstAudioCdSrc

 

track

address of GstAudioCdSrcTrack to add

 

Returns

FALSE on error, otherwise TRUE.

Types and Values

struct GstAudioCdSrc

struct GstAudioCdSrc;

struct GstAudioCdSrcClass

struct GstAudioCdSrcClass {
  GstPushSrcClass pushsrc_class;

  /* open/close the CD device */
  gboolean    (*open)               (GstAudioCdSrc *src, const gchar *device);
  void        (*close)              (GstAudioCdSrc *src);

  /* read one sector (LBA) */
  GstBuffer * (*read_sector)        (GstAudioCdSrc *src, gint sector);

#if 0
  /* return default device or NULL (optional) */
  gchar *     (*get_default_device) (GstAudioCdSrc *src);

  /* return NULL-terminated string array of CD devices, or NULL (optional) */
  /* FIXME 0.11: reconsider for new probing/device discovery API, remove if in doubt */
  gchar **    (*probe_devices)      (GstAudioCdSrc *src);
#endif
};

Audio CD source base class.

Members

GstPushSrcClass pushsrc_class;

the parent class

 

open ()

opening the device

 

close ()

closing the device

 

read_sector ()

reading a sector

 

get_default_device ()

getting the default device

 

probe_devices ()

probing possible devices

 

struct GstAudioCdSrcTrack

struct GstAudioCdSrcTrack {
  gboolean     is_audio;      /* TRUE if this is an audio track             */
  guint        num;           /* real track number (usually starts from 1)  */
  guint        start;         /* first sector of track (LBA, not LSN!)      */
  guint        end;           /* last sector of track  (LBA, not LSN!)      */
  GstTagList  *tags;          /* NULL or tags for track (e.g. from cd-text) */
};

CD track abstraction to communicate TOC entries to the base class.

This structure is only for use by sub-classed in connection with gst_audio_cd_src_add_track().

Applications will be informed of the available tracks via a TOC message on the pipeline's GstBus instead.

Members

gboolean is_audio;

Whether this is an audio track

 

guint num;

Track number in TOC (usually starts from 1, but not always)

 

guint start;

The first sector of this track (LBA)

 

guint end;

The last sector of this track (LBA)

 

GstTagList *tags;

Track-specific tags (e.g. from cd-text information), or NULL

 

enum GstAudioCdSrcMode

Mode in which the CD audio source operates. Influences timestamping, EOS handling and seeking.

Members

GST_AUDIO_CD_SRC_MODE_NORMAL

each single track is a stream

 

GST_AUDIO_CD_SRC_MODE_CONTINUOUS

the entire disc is a single stream

 

Property Details

The “device” property

  “device”                   gchar *

CD device location.

Flags: Read / Write

Default value: NULL


The “mode” property

  “mode”                     GstAudioCdSrcMode

Mode.

Flags: Read / Write

Default value: GST_AUDIO_CD_SRC_MODE_NORMAL


The “track” property

  “track”                    guint

Track.

Flags: Read / Write

Allowed values: [1,99]

Default value: 1

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