yet another sync method: probe sound card buffer size on startup

(experimental). sound cards usually have a fixed buffer (in bytes),
therefore it's delay cannot be corrected for all sample rates using some
latency setting. also this method doesn't suffer from the drift problem
as softsync.

CVS patchset: 1758
CVS date: 2002/04/23 01:06:32

1 files changed, 46 insertions, 3 deletions

diff --git a/src/audio_out/audio_oss_out.c b/src/audio_out/audio_oss_out.c
index 3fcc7942f..e624afe88 100644
--- a/src/audio_out/audio_oss_out.c
+++ b/src/audio_out/audio_oss_out.c
@@ -17,7 +17,7 @@
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA
  *
- * $Id: audio_oss_out.c,v 1.59 2002/03/11 19:58:00 jkeil Exp $
+ * $Id: audio_oss_out.c,v 1.60 2002/04/23 01:06:32 miguelfreitas Exp $
  *
  * 20-8-2001 First implementation of Audio sync and Audio driver separation.
  * Copyright (C) 2001 James Courtier-Dutton James@superbug.demon.co.uk
@@ -94,6 +94,7 @@
 #define OSS_SYNC_GETODELAY    1
 #define OSS_SYNC_GETOPTR      2
 #define OSS_SYNC_SOFTSYNC     3
+#define OSS_SYNC_PROBEBUFFER  4
 
 #ifdef CONFIG_DEVFS_FS
 #define DSP_TEMPLATE "/dev/sound/dsp%d"
@@ -121,6 +122,7 @@ typedef struct oss_driver_s {
   int              audio_started;
   int              sync_method;
   int              latency;
+  int              buffer_size;
 
   struct {
     char          *name;
@@ -333,6 +335,12 @@ static int ao_oss_delay(ao_driver_t *this_gen) {
   struct        timeval tv;
 
   switch (this->sync_method) {
+  case OSS_SYNC_PROBEBUFFER:
+    if( this->bytes_in_buffer < this->buffer_size )
+      bytes_left = this->bytes_in_buffer;
+    else
+      bytes_left = this->buffer_size;
+    break;
 
   case OSS_SYNC_SOFTSYNC:
     /* use system real-time clock to get pseudo audio frame position */
@@ -562,7 +570,7 @@ static int ao_oss_set_property (ao_driver_t *this_gen, int property, int value)
 }
 
 static int ao_oss_ctrl(ao_driver_t *this_gen, int cmd, ...) {
-  oss_driver_t *this = (oss_driver_t *) this_gen;
+  /*oss_driver_t *this = (oss_driver_t *) this_gen;*/
 
   switch (cmd) {
 
@@ -593,7 +601,7 @@ ao_driver_t *init_audio_out_plugin (config_values_t *config) {
   int              devnum;
   int              audio_fd;
   int              num_channels, status, arg;
-  static char     *sync_methods[] = {"auto", "getodelay", "getoptr", "softsync", NULL};
+  static char     *sync_methods[] = {"auto", "getodelay", "getoptr", "softsync", "probebuffer", NULL};
   
   this = (oss_driver_t *) malloc (sizeof (oss_driver_t));
 
@@ -710,6 +718,41 @@ ao_driver_t *init_audio_out_plugin (config_values_t *config) {
 
     gettimeofday(&this->start_time, NULL);
   }
+  
+  if (this->sync_method == OSS_SYNC_PROBEBUFFER) {
+    char *buf;
+    int c;
+  
+    printf ("audio_oss_out: Audio driver realtime sync disabled...\n");
+    printf ("audio_oss_out: ...probing output buffer size: ");
+    this->buffer_size = 0;
+    
+    if( (buf=malloc(1024)) != NULL ) {
+      memset(buf,0,1024);
+     
+      do {
+        c = write(audio_fd,buf,1024);
+        if( c != -1 )
+          this->buffer_size += c;
+      } while( c == 1024 );
+      
+      free(buf);
+    }
+    close(audio_fd);
+    printf ("%d bytes\n", this->buffer_size );
+    printf ("audio_oss_out: ...there may be audio/video synchronization issues\n");
+  
+    audio_fd=open(this->audio_dev, O_WRONLY|O_NONBLOCK);
+
+    if(audio_fd < 0) 
+    {
+      printf("audio_oss_out: opening audio device %s failed:\n%s\n",
+	   this->audio_dev, strerror(errno));
+
+      free (this);
+      return NULL;
+    }
+  }
 
   this->latency = config->register_range (config, "audio.oss_latency", 0,
 					  -3000, 3000,