154 lines
3.6 KiB
ReStructuredText
154 lines
3.6 KiB
ReStructuredText
.. -*- coding: utf-8; mode: rst -*-
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.. _audio_data_types:
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****************
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Audio Data Types
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****************
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This section describes the structures, data types and defines used when
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talking to the audio device.
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.. c:type:: audio_stream_source
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The audio stream source is set through the AUDIO_SELECT_SOURCE call
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and can take the following values, depending on whether we are replaying
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from an internal (demux) or external (user write) source.
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.. code-block:: c
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typedef enum {
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AUDIO_SOURCE_DEMUX,
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AUDIO_SOURCE_MEMORY
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} audio_stream_source_t;
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AUDIO_SOURCE_DEMUX selects the demultiplexer (fed either by the
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frontend or the DVR device) as the source of the video stream. If
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AUDIO_SOURCE_MEMORY is selected the stream comes from the application
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through the ``write()`` system call.
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.. c:type:: audio_play_state
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The following values can be returned by the AUDIO_GET_STATUS call
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representing the state of audio playback.
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.. code-block:: c
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typedef enum {
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AUDIO_STOPPED,
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AUDIO_PLAYING,
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AUDIO_PAUSED
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} audio_play_state_t;
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.. c:type:: audio_channel_select
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The audio channel selected via AUDIO_CHANNEL_SELECT is determined by
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the following values.
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.. code-block:: c
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typedef enum {
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AUDIO_STEREO,
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AUDIO_MONO_LEFT,
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AUDIO_MONO_RIGHT,
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AUDIO_MONO,
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AUDIO_STEREO_SWAPPED
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} audio_channel_select_t;
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.. c:type:: audio_status
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The AUDIO_GET_STATUS call returns the following structure informing
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about various states of the playback operation.
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.. code-block:: c
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typedef struct audio_status {
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boolean AV_sync_state;
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boolean mute_state;
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audio_play_state_t play_state;
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audio_stream_source_t stream_source;
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audio_channel_select_t channel_select;
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boolean bypass_mode;
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audio_mixer_t mixer_state;
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} audio_status_t;
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.. c:type:: audio_mixer
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The following structure is used by the AUDIO_SET_MIXER call to set the
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audio volume.
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.. code-block:: c
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typedef struct audio_mixer {
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unsigned int volume_left;
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unsigned int volume_right;
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} audio_mixer_t;
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.. _audio_encodings:
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audio encodings
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===============
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A call to AUDIO_GET_CAPABILITIES returns an unsigned integer with the
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following bits set according to the hardwares capabilities.
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.. code-block:: c
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#define AUDIO_CAP_DTS 1
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#define AUDIO_CAP_LPCM 2
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#define AUDIO_CAP_MP1 4
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#define AUDIO_CAP_MP2 8
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#define AUDIO_CAP_MP3 16
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#define AUDIO_CAP_AAC 32
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#define AUDIO_CAP_OGG 64
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#define AUDIO_CAP_SDDS 128
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#define AUDIO_CAP_AC3 256
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.. c:type:: audio_karaoke
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The ioctl AUDIO_SET_KARAOKE uses the following format:
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.. code-block:: c
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typedef
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struct audio_karaoke {
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int vocal1;
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int vocal2;
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int melody;
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} audio_karaoke_t;
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If Vocal1 or Vocal2 are non-zero, they get mixed into left and right t
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at 70% each. If both, Vocal1 and Vocal2 are non-zero, Vocal1 gets mixed
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into the left channel and Vocal2 into the right channel at 100% each. Ff
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Melody is non-zero, the melody channel gets mixed into left and right.
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.. c:type:: audio_attributes
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The following attributes can be set by a call to AUDIO_SET_ATTRIBUTES:
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.. code-block:: c
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typedef uint16_t audio_attributes_t;
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/* bits: descr. */
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/* 15-13 audio coding mode (0=ac3, 2=mpeg1, 3=mpeg2ext, 4=LPCM, 6=DTS, */
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/* 12 multichannel extension */
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/* 11-10 audio type (0=not spec, 1=language included) */
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/* 9- 8 audio application mode (0=not spec, 1=karaoke, 2=surround) */
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/* 7- 6 Quantization / DRC (mpeg audio: 1=DRC exists)(lpcm: 0=16bit, */
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/* 5- 4 Sample frequency fs (0=48kHz, 1=96kHz) */
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/* 2- 0 number of audio channels (n+1 channels) */
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