.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
|
|
.. _audio_data_types:
|
|
****************
|
Audio Data Types
|
****************
|
|
This section describes the structures, data types and defines used when
|
talking to the audio device.
|
|
.. c:type:: audio_stream_source
|
|
The audio stream source is set through the AUDIO_SELECT_SOURCE call
|
and can take the following values, depending on whether we are replaying
|
from an internal (demux) or external (user write) source.
|
|
|
.. code-block:: c
|
|
typedef enum {
|
AUDIO_SOURCE_DEMUX,
|
AUDIO_SOURCE_MEMORY
|
} audio_stream_source_t;
|
|
AUDIO_SOURCE_DEMUX selects the demultiplexer (fed either by the
|
frontend or the DVR device) as the source of the video stream. If
|
AUDIO_SOURCE_MEMORY is selected the stream comes from the application
|
through the ``write()`` system call.
|
|
|
.. c:type:: audio_play_state
|
|
The following values can be returned by the AUDIO_GET_STATUS call
|
representing the state of audio playback.
|
|
|
.. code-block:: c
|
|
typedef enum {
|
AUDIO_STOPPED,
|
AUDIO_PLAYING,
|
AUDIO_PAUSED
|
} audio_play_state_t;
|
|
|
.. c:type:: audio_channel_select
|
|
The audio channel selected via AUDIO_CHANNEL_SELECT is determined by
|
the following values.
|
|
|
.. code-block:: c
|
|
typedef enum {
|
AUDIO_STEREO,
|
AUDIO_MONO_LEFT,
|
AUDIO_MONO_RIGHT,
|
AUDIO_MONO,
|
AUDIO_STEREO_SWAPPED
|
} audio_channel_select_t;
|
|
|
.. c:type:: audio_status
|
|
The AUDIO_GET_STATUS call returns the following structure informing
|
about various states of the playback operation.
|
|
|
.. code-block:: c
|
|
typedef struct audio_status {
|
boolean AV_sync_state;
|
boolean mute_state;
|
audio_play_state_t play_state;
|
audio_stream_source_t stream_source;
|
audio_channel_select_t channel_select;
|
boolean bypass_mode;
|
audio_mixer_t mixer_state;
|
} audio_status_t;
|
|
|
.. c:type:: audio_mixer
|
|
The following structure is used by the AUDIO_SET_MIXER call to set the
|
audio volume.
|
|
|
.. code-block:: c
|
|
typedef struct audio_mixer {
|
unsigned int volume_left;
|
unsigned int volume_right;
|
} audio_mixer_t;
|
|
|
.. _audio_encodings:
|
|
audio encodings
|
===============
|
|
A call to AUDIO_GET_CAPABILITIES returns an unsigned integer with the
|
following bits set according to the hardwares capabilities.
|
|
|
.. code-block:: c
|
|
#define AUDIO_CAP_DTS 1
|
#define AUDIO_CAP_LPCM 2
|
#define AUDIO_CAP_MP1 4
|
#define AUDIO_CAP_MP2 8
|
#define AUDIO_CAP_MP3 16
|
#define AUDIO_CAP_AAC 32
|
#define AUDIO_CAP_OGG 64
|
#define AUDIO_CAP_SDDS 128
|
#define AUDIO_CAP_AC3 256
|
