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.. -*- coding: utf-8; mode: rst -*-
.. _audio_data_types:
****************
Audio Data Types
****************
This section describes the structures, data types and defines used when
talking to the audio device.
.. _audio-stream-source-t:
audio_stream_source_t
=====================
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.
.. _audio-play-state-t:
audio_play_state_t
==================
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;
.. _audio-channel-select-t:
audio_channel_select_t
======================
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;
.. _audio-status:
struct 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;
.. _audio-mixer:
struct 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
.. _audio-karaoke:
struct audio_karaoke
====================
The ioctl AUDIO_SET_KARAOKE uses the following format:
.. code-block:: c
typedef
struct audio_karaoke {
int vocal1;
int vocal2;
int melody;
} audio_karaoke_t;
If Vocal1 or Vocal2 are non-zero, they get mixed into left and right t
at 70% each. If both, Vocal1 and Vocal2 are non-zero, Vocal1 gets mixed
into the left channel and Vocal2 into the right channel at 100% each. Ff
Melody is non-zero, the melody channel gets mixed into left and right.
.. _audio-attributes-t:
audio attributes
================
The following attributes can be set by a call to AUDIO_SET_ATTRIBUTES:
.. code-block:: c
typedef uint16_t audio_attributes_t;
/* bits: descr. */
/* 15-13 audio coding mode (0=ac3, 2=mpeg1, 3=mpeg2ext, 4=LPCM, 6=DTS, */
/* 12 multichannel extension */
/* 11-10 audio type (0=not spec, 1=language included) */
/* 9- 8 audio application mode (0=not spec, 1=karaoke, 2=surround) */
/* 7- 6 Quantization / DRC (mpeg audio: 1=DRC exists)(lpcm: 0=16bit, */
/* 5- 4 Sample frequency fs (0=48kHz, 1=96kHz) */
/* 2- 0 number of audio channels (n+1 channels) */
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