Thanks for your response. I am pasting below the contents of oss.c code for information. I would appreciate your help in modifying/tweaking this code so that I also get 5.1 surround sound in VLC using OSS4.
oss.c
/*****************************************************************************
* oss.c : OSS /dev/dsp module for vlc
*****************************************************************************
* Copyright (C) 2000-2002 the VideoLAN team
* $Id: 14d91ca1c0efa9a3d196006d4bea70f2742708fe $
*
* Authors: Michel Kaempf <
maxx@via.ecp.fr>
* Sam Hocevar <
sam@zoy.org>
* Christophe Massiot <
massiot@via.ecp.fr>
*
* 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 <fcntl.h> /* open(), O_WRONLY */
#include <sys/ioctl.h> /* ioctl() */
#include <unistd.h> /* write(), close() */
#include <vlc_common.h>
#include <vlc_plugin.h>
#include <vlc_fs.h>
#include <vlc_aout.h>
/* SNDCTL_DSP_RESET, SNDCTL_DSP_SETFMT, SNDCTL_DSP_STEREO, SNDCTL_DSP_SPEED,
* SNDCTL_DSP_GETOSPACE */
#ifdef HAVE_SOUNDCARD_H
# include <soundcard.h>
#elif defined( HAVE_SYS_SOUNDCARD_H )
# include <sys/soundcard.h>
#endif
/* Patches for ignorant OSS versions */
#ifndef AFMT_AC3
# define AFMT_AC3 0x00000400 /* Dolby Digital AC3 */
#endif
#ifndef AFMT_S16_NE
# ifdef WORDS_BIGENDIAN
# define AFMT_S16_NE AFMT_S16_BE
# else
# define AFMT_S16_NE AFMT_S16_LE
# endif
#endif
/*****************************************************************************
* aout_sys_t: OSS audio output method descriptor
*****************************************************************************
* This structure is part of the audio output thread descriptor.
* It describes the DSP specific properties of an audio device.
*****************************************************************************/
struct aout_sys_t
{
int i_fd;
int b_workaround_buggy_driver;
int i_fragstotal;
mtime_t max_buffer_duration;
};
/* This must be a power of 2. */
#define FRAME_SIZE 1024
#define FRAME_COUNT 32
/*****************************************************************************
* Local prototypes
*****************************************************************************/
static int Open ( vlc_object_t * );
static void Close ( vlc_object_t * );
static void Play ( aout_instance_t * );
static void* OSSThread ( vlc_object_t * );
static mtime_t BufferDuration( aout_instance_t * p_aout );
/*****************************************************************************
* Module descriptor
*****************************************************************************/
#define BUGGY_TEXT N_("Try to work around buggy OSS drivers")
#define BUGGY_LONGTEXT N_( \
"Some buggy OSS drivers just don't like when their internal buffers " \
"are completely filled (the sound gets heavily hashed). If you have one " \
"of these drivers, then you need to enable this option." )
vlc_module_begin ()
set_shortname( "OSS" )
set_description( N_("UNIX OSS audio output") )
set_category( CAT_AUDIO )
set_subcategory( SUBCAT_AUDIO_AOUT )
add_file( "oss-audio-device", "/dev/dsp", aout_FindAndRestart,
N_("OSS DSP device"), NULL, false )
add_deprecated_alias( "dspdev" ) /* deprecated since 0.9.3 */
add_bool( "oss-buggy", false, NULL, BUGGY_TEXT, BUGGY_LONGTEXT, true )
set_capability( "audio output", 100 )
add_shortcut( "oss" )
set_callbacks( Open, Close )
vlc_module_end ()
/*****************************************************************************
* Probe: probe the audio device for available formats and channels
*****************************************************************************/
static void Probe( aout_instance_t * p_aout )
{
struct aout_sys_t * p_sys = p_aout->output.p_sys;
vlc_value_t val, text;
int i_format, i_nb_channels;
var_Create( p_aout, "audio-device", VLC_VAR_INTEGER | VLC_VAR_HASCHOICE );
text.psz_string = _("Audio Device");
var_Change( p_aout, "audio-device", VLC_VAR_SETTEXT, &text, NULL );
/* Test for multi-channel. */
#ifdef SNDCTL_DSP_GETCHANNELMASK
if ( aout_FormatNbChannels( &p_aout->output.output ) > 2 )
{
/* Check that the device supports this. */
int i_chanmask;
/* Reset all. */
i_format = AFMT_S16_NE;
if( ioctl( p_sys->i_fd, SNDCTL_DSP_RESET, NULL ) < 0 ||
ioctl( p_sys->i_fd, SNDCTL_DSP_SETFMT, &i_format ) < 0 )
{
msg_Err( p_aout, "cannot reset OSS audio device" );
var_Destroy( p_aout, "audio-device" );
return;
}
if ( ioctl( p_sys->i_fd, SNDCTL_DSP_GETCHANNELMASK,
&i_chanmask ) == 0 )
{
if ( !(i_chanmask & DSP_BIND_FRONT) )
{
msg_Err( p_aout, "no front channels! (%x)",
i_chanmask );
return;
}
if ( (i_chanmask & (DSP_BIND_SURR | DSP_BIND_CENTER_LFE))
&& (p_aout->output.output.i_physical_channels ==
(AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
| AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT
| AOUT_CHAN_LFE)) )
{
val.i_int = AOUT_VAR_5_1;
text.psz_string = (char*) "5.1";
var_Change( p_aout, "audio-device",
VLC_VAR_ADDCHOICE, &val, &text );
}
if ( (i_chanmask & DSP_BIND_SURR)
&& (p_aout->output.output.i_physical_channels &
(AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
| AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT)) )
{
val.i_int = AOUT_VAR_2F2R;
text.psz_string = _("2 Front 2 Rear");
var_Change( p_aout, "audio-device",
VLC_VAR_ADDCHOICE, &val, &text );
}
}
}
#endif
/* Reset all. */
i_format = AFMT_S16_NE;
if( ioctl( p_sys->i_fd, SNDCTL_DSP_RESET, NULL ) < 0 ||
ioctl( p_sys->i_fd, SNDCTL_DSP_SETFMT, &i_format ) < 0 )
{
msg_Err( p_aout, "cannot reset OSS audio device" );
var_Destroy( p_aout, "audio-device" );
return;
}
/* Test for stereo. */
i_nb_channels = 2;
if( ioctl( p_sys->i_fd, SNDCTL_DSP_CHANNELS, &i_nb_channels ) >= 0
&& i_nb_channels == 2 )
{
val.i_int = AOUT_VAR_STEREO;
text.psz_string = _("Stereo");
var_Change( p_aout, "audio-device", VLC_VAR_ADDCHOICE, &val, &text );
}
/* Reset all. */
i_format = AFMT_S16_NE;
if( ioctl( p_sys->i_fd, SNDCTL_DSP_RESET, NULL ) < 0 ||
ioctl( p_sys->i_fd, SNDCTL_DSP_SETFMT, &i_format ) < 0 )
{
msg_Err( p_aout, "cannot reset OSS audio device" );
var_Destroy( p_aout, "audio-device" );
return;
}
/* Test for mono. */
i_nb_channels = 1;
if( ioctl( p_sys->i_fd, SNDCTL_DSP_CHANNELS, &i_nb_channels ) >= 0
&& i_nb_channels == 1 )
{
val.i_int = AOUT_VAR_MONO;
text.psz_string = _("Mono");
var_Change( p_aout, "audio-device", VLC_VAR_ADDCHOICE, &val, &text );
if ( p_aout->output.output.i_physical_channels == AOUT_CHAN_CENTER )
{
var_Set( p_aout, "audio-device", val );
}
}
if( ioctl( p_sys->i_fd, SNDCTL_DSP_RESET, NULL ) < 0 )
{
msg_Err( p_aout, "cannot reset OSS audio device" );
var_Destroy( p_aout, "audio-device" );
return;
}
/* Test for
spdif. */
if ( AOUT_FMT_NON_LINEAR( &p_aout->output.output ) )
{
i_format = AFMT_AC3;
if( ioctl( p_sys->i_fd, SNDCTL_DSP_SETFMT, &i_format ) >= 0
&& i_format == AFMT_AC3 )
{
val.i_int = AOUT_VAR_SPDIF;
text.psz_string = _("A/52 over S/PDIF");
var_Change( p_aout, "audio-device",
VLC_VAR_ADDCHOICE, &val, &text );
if( var_InheritBool( p_aout, "
spdif" ) )
var_Set( p_aout, "audio-device", val );
}
else if( var_InheritBool( p_aout, "
spdif" ) )
{
msg_Warn( p_aout, "S/PDIF not supported by card" );
}
}
var_AddCallback( p_aout, "audio-device", aout_ChannelsRestart,
NULL );
}
/*****************************************************************************
* Open: open the audio device (the digital sound processor)
*****************************************************************************
* This function opens the DSP as a usual non-blocking write-only file, and
* modifies the p_aout->p_sys->i_fd with the file's descriptor.
*****************************************************************************/
static int Open( vlc_object_t *p_this )
{
aout_instance_t * p_aout = (aout_instance_t *)p_this;
struct aout_sys_t * p_sys;
char * psz_device;
vlc_value_t val;
/* Allocate structure */
p_aout->output.p_sys = p_sys = malloc( sizeof( aout_sys_t ) );
if( p_sys == NULL )
return VLC_ENOMEM;
/* Get device name */
if( (psz_device = var_InheritString( p_aout, "oss-audio-device" )) == NULL )
{
msg_Err( p_aout, "no audio device specified (maybe /dev/dsp?)" );
free( p_sys );
return VLC_EGENERIC;
}
/* Open the sound device in non-blocking mode, because ALSA's OSS
* emulation and some broken OSS drivers would make a blocking call
* wait forever until the device is available. Since this breaks the
* OSS spec, we immediately put it back to blocking mode if the
* operation was successful. */
p_sys->i_fd = vlc_open( psz_device, O_WRONLY | O_NDELAY );
if( p_sys->i_fd < 0 )
{
msg_Err( p_aout, "cannot open audio device (%s)", psz_device );
free( psz_device );
free( p_sys );
return VLC_EGENERIC;
}
/* if the opening was ok, put the device back in blocking mode */
fcntl( p_sys->i_fd, F_SETFL,
fcntl( p_sys->i_fd, F_GETFL ) &~ FNDELAY );
free( psz_device );
p_aout->output.pf_play = Play;
if ( var_Type( p_aout, "audio-device" ) == 0 )
{
Probe( p_aout );
}
if ( var_Get( p_aout, "audio-device", &val ) < 0 )
{
/* Probe() has failed. */
close( p_sys->i_fd );
free( p_sys );
return VLC_EGENERIC;
}
if ( val.i_int == AOUT_VAR_SPDIF )
{
p_aout->output.output.i_format = VLC_CODEC_SPDIFL;
}
else if ( val.i_int == AOUT_VAR_5_1 )
{
p_aout->output.output.i_format = VLC_CODEC_S16N;
p_aout->output.output.i_physical_channels
= AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT | AOUT_CHAN_CENTER
| AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT
| AOUT_CHAN_LFE;
}
else if ( val.i_int == AOUT_VAR_2F2R )
{
p_aout->output.output.i_format = VLC_CODEC_S16N;
p_aout->output.output.i_physical_channels
= AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT
| AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT;
}
else if ( val.i_int == AOUT_VAR_STEREO )
{
p_aout->output.output.i_format = VLC_CODEC_S16N;
p_aout->output.output.i_physical_channels
= AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT;
}
else if ( val.i_int == AOUT_VAR_MONO )
{
p_aout->output.output.i_format = VLC_CODEC_S16N;
p_aout->output.output.i_physical_channels = AOUT_CHAN_CENTER;
}
else
{
/* This should not happen ! */
msg_Err( p_aout, "internal: can't find audio-device (%i)", val.i_int );
close( p_sys->i_fd );
free( p_sys );
return VLC_EGENERIC;
}
var_SetBool( p_aout, "intf-change", true );
/* Reset the DSP device */
if( ioctl( p_sys->i_fd, SNDCTL_DSP_RESET, NULL ) < 0 )
{
msg_Err( p_aout, "cannot reset OSS audio device" );
close( p_sys->i_fd );
free( p_sys );
return VLC_EGENERIC;
}
/* Set the output format */
if ( AOUT_FMT_NON_LINEAR( &p_aout->output.output ) )
{
int i_format = AFMT_AC3;
if( ioctl( p_sys->i_fd, SNDCTL_DSP_SETFMT, &i_format ) < 0
|| i_format != AFMT_AC3 )
{
msg_Err( p_aout, "cannot reset OSS audio device" );
close( p_sys->i_fd );
free( p_sys );
return VLC_EGENERIC;
}
p_aout->output.output.i_format = VLC_CODEC_SPDIFL;
p_aout->output.i_nb_samples = A52_FRAME_NB;
p_aout->output.output.i_bytes_per_frame = AOUT_SPDIF_SIZE;
p_aout->output.output.i_frame_length = A52_FRAME_NB;
aout_VolumeNoneInit( p_aout );
}
if ( !AOUT_FMT_NON_LINEAR( &p_aout->output.output ) )
{
unsigned int i_format = AFMT_S16_NE;
unsigned int i_frame_size, i_fragments;
unsigned int i_rate;
unsigned int i_nb_channels;
audio_buf_info audio_buf;
if( ioctl( p_sys->i_fd, SNDCTL_DSP_SETFMT, &i_format ) < 0 )
{
msg_Err( p_aout, "cannot set audio output format" );
close( p_sys->i_fd );
free( p_sys );
return VLC_EGENERIC;
}
switch ( i_format )
{
case AFMT_U8:
p_aout->output.output.i_format = VLC_CODEC_U8;
break;
case AFMT_S8:
p_aout->output.output.i_format = VLC_CODEC_S8;
break;
case AFMT_U16_LE:
p_aout->output.output.i_format = VLC_CODEC_U16L;
break;
case AFMT_S16_LE:
p_aout->output.output.i_format = VLC_CODEC_S16L;
break;
case AFMT_U16_BE:
p_aout->output.output.i_format = VLC_CODEC_U16B;
break;
case AFMT_S16_BE:
p_aout->output.output.i_format = VLC_CODEC_S16B;
break;
default:
msg_Err( p_aout, "OSS fell back to an unknown format (%d)",
i_format );
close( p_sys->i_fd );
free( p_sys );
return VLC_EGENERIC;
}
i_nb_channels = aout_FormatNbChannels( &p_aout->output.output );
/* Set the number of channels */
if( ioctl( p_sys->i_fd, SNDCTL_DSP_CHANNELS, &i_nb_channels ) < 0 ||
i_nb_channels != aout_FormatNbChannels( &p_aout->output.output ) )
{
msg_Err( p_aout, "cannot set number of audio channels (%s)",
aout_FormatPrintChannels( &p_aout->output.output) );
close( p_sys->i_fd );
free( p_sys );
return VLC_EGENERIC;
}
/* Set the output rate */
i_rate = p_aout->output.output.i_rate;
if( ioctl( p_sys->i_fd, SNDCTL_DSP_SPEED, &i_rate ) < 0 )
{
msg_Err( p_aout, "cannot set audio output rate (%i)",
p_aout->output.output.i_rate );
close( p_sys->i_fd );
free( p_sys );
return VLC_EGENERIC;
}
if( i_rate != p_aout->output.output.i_rate )
{
p_aout->output.output.i_rate = i_rate;
}
/* Set the fragment size */
aout_FormatPrepare( &p_aout->output.output );
/* i_fragment = xxxxyyyy where: xxxx is fragtotal
* 1 << yyyy is fragsize */
i_frame_size = ((uint64_t)p_aout->output.output.i_bytes_per_frame * p_aout->output.output.i_rate * 65536) / (48000 * 2 * 2) / FRAME_COUNT;
i_fragments = 4;
while( i_fragments < 12 && (1U << i_fragments) < i_frame_size )
{
++i_fragments;
}
i_fragments |= FRAME_COUNT << 16;
if( ioctl( p_sys->i_fd, SNDCTL_DSP_SETFRAGMENT, &i_fragments ) < 0 )
{
msg_Warn( p_aout, "cannot set fragment size (%.8x)", i_fragments );
}
if( ioctl( p_sys->i_fd, SNDCTL_DSP_GETOSPACE, &audio_buf ) < 0 )
{
msg_Err( p_aout, "cannot get fragment size" );
close( p_sys->i_fd );
free( p_sys );
return VLC_EGENERIC;
}
else
{
/* Number of fragments actually allocated */
p_aout->output.p_sys->i_fragstotal = audio_buf.fragstotal;
/* Maximum duration the soundcard's buffer can hold */
p_aout->output.p_sys->max_buffer_duration =
(mtime_t)audio_buf.fragstotal * audio_buf.fragsize * 1000000
/ p_aout->output.output.i_bytes_per_frame
/ p_aout->output.output.i_rate
* p_aout->output.output.i_frame_length;
p_aout->output.i_nb_samples = audio_buf.fragsize /
p_aout->output.output.i_bytes_per_frame;
}
aout_VolumeSoftInit( p_aout );
}
p_aout->output.p_sys->b_workaround_buggy_driver =
var_InheritBool( p_aout, "oss-buggy" );
/* Create OSS thread and wait for its readiness. */
if( vlc_thread_create( p_aout, "aout", OSSThread,
VLC_THREAD_PRIORITY_OUTPUT ) )
{
msg_Err( p_aout, "cannot create OSS thread (%m)" );
close( p_sys->i_fd );
free( p_sys );
return VLC_ENOMEM;
}
return VLC_SUCCESS;
}
/*****************************************************************************
* Play: nothing to do
*****************************************************************************/
static void Play( aout_instance_t *p_aout )
{
VLC_UNUSED(p_aout);
}
/*****************************************************************************
* Close: close the DSP audio device
*****************************************************************************/
static void Close( vlc_object_t * p_this )
{
aout_instance_t *p_aout = (aout_instance_t *)p_this;
struct aout_sys_t * p_sys = p_aout->output.p_sys;
vlc_object_kill( p_aout );
vlc_thread_join( p_aout );
p_aout->b_die = false;
ioctl( p_sys->i_fd, SNDCTL_DSP_RESET, NULL );
close( p_sys->i_fd );
free( p_sys );
}
/*****************************************************************************
* BufferDuration: buffer status query
*****************************************************************************
* This function returns the duration in microseconds of the current buffer.
*****************************************************************************/
static mtime_t BufferDuration( aout_instance_t * p_aout )
{
struct aout_sys_t * p_sys = p_aout->output.p_sys;
audio_buf_info audio_buf;
int i_bytes;
/* Fill the audio_buf_info structure:
* - fragstotal: total number of fragments allocated
* - fragsize: size of a fragment in bytes
* - bytes: available space in bytes (includes partially used fragments)
* Note! 'bytes' could be more than fragments*fragsize */
ioctl( p_sys->i_fd, SNDCTL_DSP_GETOSPACE, &audio_buf );
/* calculate number of available fragments (not partially used ones) */
i_bytes = (audio_buf.fragstotal * audio_buf.fragsize) - audio_buf.bytes;
/* Return the fragment duration */
return (mtime_t)i_bytes * 1000000
/ p_aout->output.output.i_bytes_per_frame
/ p_aout->output.output.i_rate
* p_aout->output.output.i_frame_length;
}
/*****************************************************************************
* OSSThread: asynchronous thread used to DMA the data to the device
*****************************************************************************/
static void* OSSThread( vlc_object_t *p_this )
{
aout_instance_t * p_aout = (aout_instance_t*)p_this;
struct aout_sys_t * p_sys = p_aout->output.p_sys;
mtime_t next_date = 0;
int canc = vlc_savecancel ();
while ( vlc_object_alive (p_aout) )
{
aout_buffer_t * p_buffer = NULL;
int i_tmp, i_size;
uint8_t * p_bytes;
if ( p_aout->output.output.i_format != VLC_CODEC_SPDIFL )
{
mtime_t buffered = BufferDuration( p_aout );
if( p_aout->output.p_sys->b_workaround_buggy_driver )
{
#define i_fragstotal p_aout->output.p_sys->i_fragstotal
/* Wait a bit - we don't want our buffer to be full */
if( buffered > (p_aout->output.p_sys->max_buffer_duration
/ i_fragstotal * (i_fragstotal - 1)) )
{
msleep((p_aout->output.p_sys->max_buffer_duration
/ i_fragstotal ));
buffered = BufferDuration( p_aout );
}
#undef i_fragstotal
}
/* Next buffer will be played at mdate() + buffered */
p_buffer = aout_OutputNextBuffer( p_aout, mdate() + buffered,
false );
if( p_buffer == NULL &&
buffered > ( p_aout->output.p_sys->max_buffer_duration
/ p_aout->output.p_sys->i_fragstotal ) )
{
/* If we have at least a fragment full, then we can wait a
* little and retry to get a new audio buffer instead of
* playing a blank sample */
msleep( ( p_aout->output.p_sys->max_buffer_duration
/ p_aout->output.p_sys->i_fragstotal / 2 ) );
continue;
}
}
else
{
/* emu10k1 driver does not report Buffer Duration correctly in
* passthrough mode so we have to cheat */
if( !next_date )
{
next_date = mdate();
}
else
{
mtime_t delay = next_date - mdate();
if( delay > AOUT_PTS_TOLERANCE )
{
msleep( delay / 2 );
}
}
while( vlc_object_alive (p_aout) && ! ( p_buffer =
aout_OutputNextBuffer( p_aout, next_date, true ) ) )
{
msleep( VLC_HARD_MIN_SLEEP );
next_date = mdate();
}
}
if ( p_buffer != NULL )
{
p_bytes = p_buffer->p_buffer;
i_size = p_buffer->i_buffer;
/* This is theoretical ... we'll see next iteration whether
* we're drifting */
next_date += p_buffer->i_length;
}
else
{
i_size = FRAME_SIZE / p_aout->output.output.i_frame_length
* p_aout->output.output.i_bytes_per_frame;
p_bytes = malloc( i_size );
memset( p_bytes, 0, i_size );
next_date = 0;
}
i_tmp = write( p_sys->i_fd, p_bytes, i_size );
if( i_tmp < 0 )
{
msg_Err( p_aout, "write failed (%m)" );
}
if ( p_buffer != NULL )
{
aout_BufferFree( p_buffer );
}
else
{
free( p_bytes );
}
}
vlc_restorecancel (canc);
return NULL;
}
