[vlc-devel] [RFC] Android OpenSL ES audio output

Rémi Denis-Courmont remi at remlab.net
Wed Jun 1 16:21:25 CEST 2011


Inline
>
/*****************************************************************************
>  * opensles.c : audio output for android native code

OpenSL ES is a standard. As long as this file is Android-specific, it
probably should not be called opensles.c. Otherwise, we are screwed when
someone writes a plain standard OpenSL ES plugin.

> 
*****************************************************************************
>  * Copyright © 2011 VideoLAN
>  *
>  * Authors: Dominique Martinet <asmadeus at codewreck.org>
>  *          Hugo Beauzée-Luyssen <beauze.h at gmail.com>
>  *
>  * This program is free software; you can redistribute it and/or modify
>  * it under the terms of the GNU General Public License as published by
>  * the Free Software Foundation; either version 2 of the License, or
>  * (at your option) any later version.
>  *
>  * This program is distributed in the hope that it will be useful,
>  * but WITHOUT ANY WARRANTY; without even the implied warranty of
>  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>  * GNU General Public License for more details.
>  *
>  * You should have received a copy of the GNU General Public License
>  * along with this program; if not, write to the Free Software
Foundation,
>  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
> 
*****************************************************************************/
> 
>
/*****************************************************************************
>  * Preamble
> 
*****************************************************************************/
> 
> #ifdef HAVE_CONFIG_H
> # include "config.h"
> #endif
> 
> #include <vlc_common.h>
> #include <vlc_plugin.h>
> #include <vlc_aout.h>
> #include <assert.h>
> #include <dlfcn.h>
> 
> // For native audio
> #include <SLES/OpenSLES.h>
> #include <SLES/OpenSLES_Android.h>
> 
> #define BUFF_QUEUE  42

Undocumented magic number.

> 
>
/*****************************************************************************
>  * aout_sys_t: audio output method descriptor
> 
*****************************************************************************
>  * This structure is part of the audio output thread descriptor.
>  * It describes the direct sound specific properties of an audio device.
> 
*****************************************************************************/
> struct aout_sys_t
> {
>     SLObjectItf                     engineObject;
>     SLEngineItf                     engineEngine;
>     SLObjectItf                     outputMixObject;
>     SLAndroidSimpleBufferQueueItf   playerBufferQueue;
>     SLObjectItf                     playerObject;
>     SLPlayItf                       playerPlay;
>     aout_buffer_t                ** p_buffer_array;

Fixed-size array would be simpler. Or even linked list (aout_buffer_t has
->p_next).

>     int                             i_toclean_buffer;
>     int                             i_toappend_buffer;
>     SLInterfaceID                 * SL_IID_ENGINE;
>     SLInterfaceID                 * SL_IID_ANDROIDSIMPLEBUFFERQUEUE;
>     SLInterfaceID                 * SL_IID_VOLUME;
>     SLInterfaceID                 * SL_IID_PLAY;
>     void                          * p_so_handle;
> };
> 
> typedef SLresult (*slCreateEngine_t)(
>         SLObjectItf*, SLuint32, const SLEngineOption*, SLuint32,
>         const SLInterfaceID*, const SLboolean* );
> 
>
/*****************************************************************************
>  * Local prototypes.
> 
*****************************************************************************/
> static int  Open        ( vlc_object_t * );
> static void Close       ( vlc_object_t * );
> static void Play        ( aout_instance_t * );
> static void PlayedCallback ( SLAndroidSimpleBufferQueueItf caller,  void
*pContext);
> 
>
/*****************************************************************************
>  * Module descriptor
> 
*****************************************************************************/
> 
> vlc_module_begin ()
>     set_description( N_("OpenSLES audio output") )
>     set_shortname( N_("OpenSLES") )
>     set_category( CAT_AUDIO )
>     set_subcategory( SUBCAT_AUDIO_AOUT )
> 
>     set_capability( "audio output", 170 )
>     add_shortcut( "opensles", "android" )
>     set_callbacks( Open, Close )
> vlc_module_end ()
> 
> 
> #define CHECK_OPENSL_ERROR( res, msg )              \
>     if( unlikely( res != SL_RESULT_SUCCESS ) )      \
>     {                                               \
>         msg_Err( p_aout, msg" (%lu)", res );        \
>         goto error;                                 \
>     }                                               \
> 
> #define OPENSL_DLSYM( dest, handle, name )                  \
>     dest = (typeof(dest))dlsym( handle, name );             \

Fine with me here, but this is a GCCism.

>     if( dest == NULL )                                      \
>     {                                                       \
>         msg_Err( p_aout, "Failed to load symbol "name );    \

" %s", name would allow the compiler to reuse both strings.

>         goto error;                                         \
>     }                                                       \
> 
> static void Clear( aout_sys_t *p_sys )
> {
>     // Destroy buffer queue audio player object
>     // and invalidate all associated interfaces
>     if( p_sys->playerObject != NULL )
>         (*p_sys->playerObject)->Destroy( p_sys->playerObject );
> 
>     // destroy output mix object, and invalidate all associated
interfaces
>     if( p_sys->outputMixObject != NULL )
>         (*p_sys->outputMixObject)->Destroy( p_sys->outputMixObject );
> 
>     // destroy engine object, and invalidate all associated interfaces
>     if( p_sys->engineObject != NULL )
>         (*p_sys->engineObject)->Destroy( p_sys->engineObject );
> 
>     free( p_sys->p_buffer_array );
> 
>     if( p_sys->p_so_handle != NULL )
>         dlclose( p_sys->p_so_handle );
> 
>     free( p_sys );
> }
> 
>
/*****************************************************************************
>  * Open: open a dummy audio device
> 
*****************************************************************************/
> static int Open( vlc_object_t * p_this )
> {
>     aout_instance_t     *p_aout = (aout_instance_t *)p_this;
>     SLresult            result;
> 
>     /* Allocate structure */
>     p_aout->output.p_sys = malloc( sizeof( aout_sys_t ) );
>     if( unlikely( p_aout->output.p_sys == NULL ) )
>         return VLC_ENOMEM;
> 
>     p_aout->output.pf_play = Play;

You should only set callbacks when you are sure to not fail.

> 
>     aout_sys_t * p_sys = p_aout->output.p_sys;
> 
>     p_sys->playerObject     = NULL;
>     p_sys->engineObject     = NULL;
>     p_sys->outputMixObject  = NULL;
>     p_sys->i_toclean_buffer = 0;
>     p_sys->i_toappend_buffer= 0;
>     p_sys->p_buffer_array   = malloc( sizeof( **p_sys->p_buffer_array )
*
>                                     BUFF_QUEUE );

sizeof() parameter seems wrong, but see above.

>     if( unlikely( p_sys->p_buffer_array == NULL ) )
>     {
>         free( p_sys );
>         return VLC_ENOMEM;
>     }
>     p_sys->p_so_handle = NULL;

Unused value.

> 
>     //Acquiring LibOpenSLES symbols :
>     p_sys->p_so_handle = dlopen( "libOpenSLES.so", RTLD_NOW );
>     if( p_sys->p_so_handle == NULL )
>     {
>         msg_Err( p_aout, "Failed to load libOpenSLES" );
>         goto error;
>     }
> 
>     slCreateEngine_t    slCreateEnginePtr = NULL;
> 
>     OPENSL_DLSYM( slCreateEnginePtr, p_sys->p_so_handle,
"slCreateEngine" );
>     OPENSL_DLSYM( p_sys->SL_IID_ANDROIDSIMPLEBUFFERQUEUE,
p_sys->p_so_handle,
>                  "SL_IID_ANDROIDSIMPLEBUFFERQUEUE" );
>     OPENSL_DLSYM( p_sys->SL_IID_ENGINE, p_sys->p_so_handle,
"SL_IID_ENGINE" );
>     OPENSL_DLSYM( p_sys->SL_IID_PLAY, p_sys->p_so_handle, "SL_IID_PLAY"
);
>     OPENSL_DLSYM( p_sys->SL_IID_VOLUME, p_sys->p_so_handle,
"SL_IID_VOLUME" );
> 
>     // create engine
>     result = slCreateEnginePtr( &p_sys->engineObject, 0, NULL, 0, NULL,
NULL );
>     CHECK_OPENSL_ERROR( result, "Failed to create engine" );
> 
>     // realize the engine in synchronous mode
>     result = (*p_sys->engineObject)->Realize( p_sys->engineObject,
>                                              SL_BOOLEAN_FALSE );
>     CHECK_OPENSL_ERROR( result, "Failed to realize engine" );
> 
>     // get the engine interface, needed to create other objects
>     result = (*p_sys->engineObject)->GetInterface( p_sys->engineObject,
>                                         *p_sys->SL_IID_ENGINE,
&p_sys->engineEngine );
>     CHECK_OPENSL_ERROR( result, "Failed to get the engine interface" );
> 
>     // create output mix, with environmental reverb specified as a
non-required interface
>     const SLInterfaceID ids1[] = { *p_sys->SL_IID_VOLUME };
>     const SLboolean req1[] = { SL_BOOLEAN_FALSE };
>     result = (*p_sys->engineEngine)->CreateOutputMix(
p_sys->engineEngine,
>                                         &p_sys->outputMixObject, 1,
ids1, req1 );
>     CHECK_OPENSL_ERROR( result, "Failed to create output mix" );
> 
>     // realize the output mix in synchronous mode
>     result = (*p_sys->outputMixObject)->Realize( p_sys->outputMixObject,
>                                                  SL_BOOLEAN_FALSE );
>     CHECK_OPENSL_ERROR( result, "Failed to realize output mix" );
> 
> 
>     // configure audio source - this defines the number of samples you
can enqueue.
>     SLDataLocator_AndroidSimpleBufferQueue loc_bufq = {
>         SL_DATALOCATOR_ANDROIDSIMPLEBUFFERQUEUE,
>         BUFF_QUEUE
>     };
> 
>     SLDataFormat_PCM format_pcm;
>     format_pcm.formatType       = SL_DATAFORMAT_PCM;
>     format_pcm.numChannels      = 2;
>     format_pcm.samplesPerSec    = ((SLuint32)
p_aout->output.output.i_rate * 1000) ;
>     format_pcm.bitsPerSample    = SL_PCMSAMPLEFORMAT_FIXED_16;
>     format_pcm.containerSize    = SL_PCMSAMPLEFORMAT_FIXED_16;
>     format_pcm.channelMask      = SL_SPEAKER_FRONT_LEFT |
SL_SPEAKER_FRONT_RIGHT;
>     format_pcm.endianness       = SL_BYTEORDER_LITTLEENDIAN;
> 
>     SLDataSource audioSrc = {&loc_bufq, &format_pcm};
> 
>     // configure audio sink
>     SLDataLocator_OutputMix loc_outmix = {
>         SL_DATALOCATOR_OUTPUTMIX,
>         p_sys->outputMixObject
>     };
>     SLDataSink audioSnk = {&loc_outmix, NULL};
> 
>     //create audio player
>     const SLInterfaceID ids2[] = {
*p_sys->SL_IID_ANDROIDSIMPLEBUFFERQUEUE };
>     const SLboolean     req2[] = { SL_BOOLEAN_TRUE };
>     result = (*p_sys->engineEngine)->CreateAudioPlayer(
p_sys->engineEngine,
>                                     &p_sys->playerObject, &audioSrc,
>                                     &audioSnk, sizeof( ids2 ) / sizeof(
*ids2 ),
>                                     ids2, req2 );
>     CHECK_OPENSL_ERROR( result, "Failed to create audio player" );
> 
>     // realize the player
>     result = (*p_sys->playerObject)->Realize( p_sys->playerObject,
>                                               SL_BOOLEAN_FALSE );
>     CHECK_OPENSL_ERROR( result, "Failed to realize player object." );
> 
>     // get the play interface
>     result = (*p_sys->playerObject)->GetInterface( p_sys->playerObject,
>                                                   *p_sys->SL_IID_PLAY,
&p_sys->playerPlay );
>     CHECK_OPENSL_ERROR( result, "Failed to get player interface." );
> 
>     // get the buffer queue interface
>     result = (*p_sys->playerObject)->GetInterface( p_sys->playerObject,
>                                                  
*p_sys->SL_IID_ANDROIDSIMPLEBUFFERQUEUE,
>                                                  
&p_sys->playerBufferQueue );
>     CHECK_OPENSL_ERROR( result, "Failed to get buff queue interface" );
> 
>     result = (*p_sys->playerBufferQueue)->RegisterCallback(
p_sys->playerBufferQueue,
>                                                            
PlayedCallback,
>                                                            
(void*)p_sys);
>     CHECK_OPENSL_ERROR( result, "Failed to register buff queue
callback." );
> 
> 
>     // set the player's state to playing
>     result = (*p_sys->playerPlay)->SetPlayState( p_sys->playerPlay,
>                                                 SL_PLAYSTATE_PLAYING );
>     CHECK_OPENSL_ERROR( result, "Failed to switch to play state" );

I expect this should be inPlay.

> 
>     // we want 16bit signed data little endian.
>     p_aout->output.output.i_format              = VLC_CODEC_S16L;
>     p_aout->output.i_nb_samples                 = 2048;
>     p_aout->output.output.i_physical_channels   = AOUT_CHAN_LEFT |
AOUT_CHAN_RIGHT;
> 
>     aout_FormatPrepare( &p_aout->output.output );
> 
>     return VLC_SUCCESS;
> error:
>     Clear( p_sys );
>     return VLC_EGENERIC;
> }
> 
>
/*****************************************************************************
>  * Close: close our file
> 
*****************************************************************************/
> static void Close( vlc_object_t * p_this )
> {
>     aout_instance_t *p_aout = (aout_instance_t *)p_this;
>     aout_sys_t      *p_sys = p_aout->output.p_sys;
> 
>     msg_Dbg( p_aout, "Closing OpenSLES" );
> 
>     (*p_sys->playerPlay)->SetPlayState( p_sys->playerPlay,
SL_PLAYSTATE_STOPPED );
>     //Flush remaining buffers if any.
>     if( p_sys->playerBufferQueue != NULL )
>         (*p_sys->playerBufferQueue)->Clear( p_sys->playerBufferQueue );
>     Clear( p_sys );
> }
> 
>
/*****************************************************************************
>  * Play: play a sound
> 
*****************************************************************************/
> static void Play( aout_instance_t * p_aout )
> {
>     aout_sys_t * p_sys = p_aout->output.p_sys;
>     aout_buffer_t *p_buffer;
> 
>     SLresult result;
> 
>     p_buffer = aout_FifoPop(p_aout, &p_aout->output.fifo);
>     if( p_buffer != NULL )
>     {
>         for (;;)
>         {
>             result = (*p_sys->playerBufferQueue)->Enqueue(
>                             p_sys->playerBufferQueue,
p_buffer->p_buffer,
>                             p_buffer->i_buffer );
>             if( result == SL_RESULT_SUCCESS )
>                 break;
> 
>             msg_Err( p_aout, "write error (%lu)", result );
>         }
>         p_sys->p_buffer_array[p_sys->i_toappend_buffer] = p_buffer;
>         if( ++p_sys->i_toappend_buffer == BUFF_QUEUE )
>             p_sys->i_toappend_buffer = 0;

You will have some "problems" if toappend_buffer reaches toclean_buffer...

>     }
>     else
>         msg_Err( p_aout, "nothing to play?" );
> }
> 
> static void PlayedCallback (SLAndroidSimpleBufferQueueItf caller, void
*pContext )
> {
>     aout_sys_t *p_sys = (aout_sys_t*)pContext;
> 
>     assert (caller == p_sys->playerBufferQueue);
> 
>     aout_BufferFree( p_sys->p_buffer_array[p_sys->i_toclean_buffer] );
>     if( ++p_sys->i_toclean_buffer == BUFF_QUEUE )
>         p_sys->i_toclean_buffer = 0;
> }
> 

Trailing line.

-- 
Rémi Denis-Courmont
http://www.remlab.net/



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