.. 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