gstaudiometa

gstaudiometa — Buffer metadata for audio downmix matrix handling

Synopsis

#include <gst/audio/gstaudiometa.h>

struct              GstAudioDownmixMeta;
GstAudioDownmixMeta * gst_buffer_add_audio_downmix_meta (GstBuffer *buffer,
                                                         const GstAudioChannelPosition *from_position,
                                                         gint from_channels,
                                                         const GstAudioChannelPosition *to_position,
                                                         gint to_channels,
                                                         const gfloat **matrix);
#define             gst_buffer_get_audio_downmix_meta   (b)
GstAudioDownmixMeta * gst_buffer_get_audio_downmix_meta_for_channels
                                                        (GstBuffer *buffer,
                                                         const GstAudioChannelPosition *to_position,
                                                         gint to_channels);
struct              GstAudioClippingMeta;
GstAudioClippingMeta * gst_buffer_add_audio_clipping_meta
                                                        (GstBuffer *buffer,
                                                         GstFormat format,
                                                         guint64 start,
                                                         guint64 end);
#define             gst_buffer_get_audio_clipping_meta  (b)

Description

GstAudioDownmixMeta defines an audio downmix matrix to be send along with audio buffers. These functions in this module help to create and attach the meta as well as extracting it.

Details

struct GstAudioDownmixMeta

struct GstAudioDownmixMeta {
  GstMeta      meta;

  GstAudioChannelPosition *from_position;
  GstAudioChannelPosition *to_position;
  gint        from_channels, to_channels;
  gfloat       **matrix;
};

Extra buffer metadata describing audio downmixing matrix. This metadata is attached to audio buffers and contains a matrix to downmix the buffer number of channels to channels.

matrix is an two-dimensional array of to_channels times from_channels coefficients, i.e. the i-th output channels is constructed by multiplicating the input channels with the coefficients in matrix[i] and taking the sum of the results.

GstMeta meta;

parent GstMeta

GstAudioChannelPosition *from_position;

the channel positions of the source

GstAudioChannelPosition *to_position;

the channel positions of the destination

gint from_channels;

the number of channels of the source

gint to_channels;

the number of channels of the destination

gfloat **matrix;

the matrix coefficients.

gst_buffer_add_audio_downmix_meta ()

GstAudioDownmixMeta * gst_buffer_add_audio_downmix_meta (GstBuffer *buffer,
                                                         const GstAudioChannelPosition *from_position,
                                                         gint from_channels,
                                                         const GstAudioChannelPosition *to_position,
                                                         gint to_channels,
                                                         const gfloat **matrix);

Attaches GstAudioDownmixMeta metadata to buffer with the given parameters.

matrix is an two-dimensional array of to_channels times from_channels coefficients, i.e. the i-th output channels is constructed by multiplicating the input channels with the coefficients in matrix[i] and taking the sum of the results.

buffer :

a GstBuffer

from_position :

the channel positions of the source. [array length=from_channels]

from_channels :

The number of channels of the source

to_position :

the channel positions of the destination. [array length=to_channels]

to_channels :

The number of channels of the destination

matrix :

The matrix coefficients.

Returns :

the GstAudioDownmixMeta on buffer. [transfer none]

gst_buffer_get_audio_downmix_meta()

#define gst_buffer_get_audio_downmix_meta(b) ((GstAudioDownmixMeta*)gst_buffer_get_meta((b), GST_AUDIO_DOWNMIX_META_API_TYPE))

gst_buffer_get_audio_downmix_meta_for_channels ()

GstAudioDownmixMeta * gst_buffer_get_audio_downmix_meta_for_channels
                                                        (GstBuffer *buffer,
                                                         const GstAudioChannelPosition *to_position,
                                                         gint to_channels);

Find the GstAudioDownmixMeta on buffer for the given destination channel positions.

buffer :

a GstBuffer

to_position :

the channel positions of the destination. [array length=to_channels]

to_channels :

The number of channels of the destination

Returns :

the GstAudioDownmixMeta on buffer. [transfer none]

struct GstAudioClippingMeta

struct GstAudioClippingMeta {
  GstMeta   meta;

  GstFormat format;
  guint64   start;
  guint64   end;
};

Extra buffer metadata describing how much audio has to be clipped from the start or end of a buffer. This is used for compressed formats, where the first frame usually has some additional samples due to encoder and decoder delays, and the last frame usually has some additional samples to be able to fill the complete last frame.

This is used to ensure that decoded data in the end has the same amount of samples, and multiply decoded streams can be gaplessly concatenated.

Note: If clipping of the start is done by adjusting the segment, this meta has to be dropped from buffers as otherwise clipping could happen twice.

GstMeta meta;

parent GstMeta

GstFormat format;

GstFormat of start and stop, GST_FORMAT_DEFAULT is samples

guint64 start;

Amount of audio to clip from start of buffer

guint64 end;

Amount of to clip from end of buffer

Since 1.8


gst_buffer_add_audio_clipping_meta ()

GstAudioClippingMeta * gst_buffer_add_audio_clipping_meta
                                                        (GstBuffer *buffer,
                                                         GstFormat format,
                                                         guint64 start,
                                                         guint64 end);

Attaches GstAudioClippingMeta metadata to buffer with the given parameters.

buffer :

a GstBuffer

format :

GstFormat of start and stop, GST_FORMAT_DEFAULT is samples

start :

Amount of audio to clip from start of buffer

end :

Amount of to clip from end of buffer

Returns :

the GstAudioClippingMeta on buffer. [transfer none]

Since 1.8


gst_buffer_get_audio_clipping_meta()

#define gst_buffer_get_audio_clipping_meta(b) ((GstAudioClippingMeta*)gst_buffer_get_meta((b), GST_AUDIO_CLIPPING_META_API_TYPE))