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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>Chapter 12. DVB Audio Device</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="LINUX MEDIA INFRASTRUCTURE API" /><link rel="up" href="pt02.html" title="Part II. LINUX DVB API" /><link rel="prev" href="ch11s02.html" title="Video Function Calls" /><link rel="next" href="ch12s02.html" title="Audio Function Calls" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 12. DVB Audio Device</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch11s02.html">Prev</a> </td><th width="60%" align="center">Part II. LINUX DVB API</th><td width="20%" align="right"> <a accesskey="n" href="ch12s02.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 12. DVB Audio Device"><div class="titlepage"><div><div><h2 class="title"><a id="dvb_audio"></a>Chapter 12. DVB Audio Device</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="ch12.html#audio_data_types">Audio Data Types</a></span></dt><dd><dl><dt><span class="section"><a href="ch12.html#audio_stream_source_t">audio_stream_source_t</a></span></dt><dt><span class="section"><a href="ch12.html#audio_play_state_t">audio_play_state_t</a></span></dt><dt><span class="section"><a href="ch12.html#audio_channel_select_t">audio_channel_select_t</a></span></dt><dt><span class="section"><a href="ch12.html#struct_audio_status">struct audio_status</a></span></dt><dt><span class="section"><a href="ch12.html#struct_audio_mixer">struct audio_mixer</a></span></dt><dt><span class="section"><a href="ch12.html#audio_encodings">audio encodings</a></span></dt><dt><span class="section"><a href="ch12.html#struct_audio_karaoke">struct audio_karaoke</a></span></dt><dt><span class="section"><a href="ch12.html#audio_attributes">audio attributes</a></span></dt></dl></dd><dt><span class="section"><a href="ch12s02.html">Audio Function Calls</a></span></dt><dd><dl><dt><span class="section"><a href="ch12s02.html#audio_fopen">open()</a></span></dt><dt><span class="section"><a href="ch12s02.html#audio_fclose">close()</a></span></dt><dt><span class="section"><a href="ch12s02.html#audio_fwrite">write()</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2864906">AUDIO_STOP</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2865047">AUDIO_PLAY</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2865188">AUDIO_PAUSE</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2865345">AUDIO_SELECT_SOURCE</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2865527">AUDIO_SET_MUTE</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2865734">AUDIO_SET_AV_SYNC</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2865942">AUDIO_SET_BYPASS_MODE</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2866154">AUDIO_CHANNEL_SELECT</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2866334">AUDIO_GET_STATUS</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2866514">AUDIO_GET_CAPABILITIES</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2866695">AUDIO_CLEAR_BUFFER</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2866837">AUDIO_SET_ID</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2867020">AUDIO_SET_MIXER</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2867199">AUDIO_SET_STREAMTYPE</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2867360">AUDIO_SET_EXT_ID</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2867521">AUDIO_SET_ATTRIBUTES</a></span></dt><dt><span class="section"><a href="ch12s02.html#id2867682">AUDIO_SET_KARAOKE</a></span></dt></dl></dd></dl></div><p>The DVB audio device controls the MPEG2 audio decoder of the DVB hardware. It
can be accessed through <span class="tt">/dev/dvb/adapter0/audio0</span>. Data types and and
ioctl definitions can be accessed by including <span class="tt">linux/dvb/video.h</span> in your
application.
</p><p>Please note that some DVB cards don’t have their own MPEG decoder, which results in
the omission of the audio and video device.
</p><div class="section" title="Audio Data Types"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="audio_data_types"></a>Audio Data Types</h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="ch12.html#audio_stream_source_t">audio_stream_source_t</a></span></dt><dt><span class="section"><a href="ch12.html#audio_play_state_t">audio_play_state_t</a></span></dt><dt><span class="section"><a href="ch12.html#audio_channel_select_t">audio_channel_select_t</a></span></dt><dt><span class="section"><a href="ch12.html#struct_audio_status">struct audio_status</a></span></dt><dt><span class="section"><a href="ch12.html#struct_audio_mixer">struct audio_mixer</a></span></dt><dt><span class="section"><a href="ch12.html#audio_encodings">audio encodings</a></span></dt><dt><span class="section"><a href="ch12.html#struct_audio_karaoke">struct audio_karaoke</a></span></dt><dt><span class="section"><a href="ch12.html#audio_attributes">audio attributes</a></span></dt></dl></div><p>This section describes the structures, data types and defines used when talking to the
audio device.
</p><div class="section" title="audio_stream_source_t"><div class="titlepage"><div><div><h3 class="title"><a id="audio_stream_source_t"></a>audio_stream_source_t</h3></div></div></div><p>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.
</p><pre class="programlisting">
typedef enum {
AUDIO_SOURCE_DEMUX,
AUDIO_SOURCE_MEMORY
} audio_stream_source_t;
</pre><p>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 <span class="tt">write()</span> system
call.
</p></div><div class="section" title="audio_play_state_t"><div class="titlepage"><div><div><h3 class="title"><a id="audio_play_state_t"></a>audio_play_state_t</h3></div></div></div><p>The following values can be returned by the AUDIO_GET_STATUS call representing the
state of audio playback.
</p><pre class="programlisting">
typedef enum {
AUDIO_STOPPED,
AUDIO_PLAYING,
AUDIO_PAUSED
} audio_play_state_t;
</pre></div><div class="section" title="audio_channel_select_t"><div class="titlepage"><div><div><h3 class="title"><a id="audio_channel_select_t"></a>audio_channel_select_t</h3></div></div></div><p>The audio channel selected via AUDIO_CHANNEL_SELECT is determined by the
following values.
</p><pre class="programlisting">
typedef enum {
AUDIO_STEREO,
AUDIO_MONO_LEFT,
AUDIO_MONO_RIGHT,
} audio_channel_select_t;
</pre></div><div class="section" title="struct audio_status"><div class="titlepage"><div><div><h3 class="title"><a id="struct_audio_status"></a>struct audio_status</h3></div></div></div><p>The AUDIO_GET_STATUS call returns the following structure informing about various
states of the playback operation.
</p><pre class="programlisting">
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_status_t;
</pre></div><div class="section" title="struct audio_mixer"><div class="titlepage"><div><div><h3 class="title"><a id="struct_audio_mixer"></a>struct audio_mixer</h3></div></div></div><p>The following structure is used by the AUDIO_SET_MIXER call to set the audio
volume.
</p><pre class="programlisting">
typedef struct audio_mixer {
unsigned int volume_left;
unsigned int volume_right;
} audio_mixer_t;
</pre></div><div class="section" title="audio encodings"><div class="titlepage"><div><div><h3 class="title"><a id="audio_encodings"></a>audio encodings</h3></div></div></div><p>A call to AUDIO_GET_CAPABILITIES returns an unsigned integer with the following
bits set according to the hardwares capabilities.
</p><pre class="programlisting">
#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
</pre></div><div class="section" title="struct audio_karaoke"><div class="titlepage"><div><div><h3 class="title"><a id="struct_audio_karaoke"></a>struct audio_karaoke</h3></div></div></div><p>The ioctl AUDIO_SET_KARAOKE uses the following format:
</p><pre class="programlisting">
typedef
struct audio_karaoke{
int vocal1;
int vocal2;
int melody;
} audio_karaoke_t;
</pre><p>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.
</p></div><div class="section" title="audio attributes"><div class="titlepage"><div><div><h3 class="title"><a id="audio_attributes"></a>audio attributes</h3></div></div></div><p>The following attributes can be set by a call to AUDIO_SET_ATTRIBUTES:
</p><pre class="programlisting">
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) ⋆/
</pre></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch11s02.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="pt02.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ch12s02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Video Function Calls </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Audio Function Calls</td></tr></table></div></body></html>
