ext/alsa/: Use alsa trigger_tstamp to get the timestamp of the first sample in the buffer for more precise sync. Some...

Original commit message from CVS:
* ext/alsa/gstalsa.c: (gst_alsa_start), (gst_alsa_xrun_recovery):
* ext/alsa/gstalsa.h:
* ext/alsa/gstalsasrc.c: (gst_alsa_src_init),
(gst_alsa_src_update_avail), (gst_alsa_src_loop):
Use alsa trigger_tstamp to get the timestamp of the first
sample in the buffer for more precise sync. Some cleanups.

ChangeLog

@@ -1,3 +1,12 @@
+2004-06-24  Wim Taymans  <wim@fluendo.com>
+
+	* ext/alsa/gstalsa.c: (gst_alsa_start), (gst_alsa_xrun_recovery):
+	* ext/alsa/gstalsa.h:
+	* ext/alsa/gstalsasrc.c: (gst_alsa_src_init),
+	(gst_alsa_src_update_avail), (gst_alsa_src_loop):
+	Use alsa trigger_tstamp to get the timestamp of the first
+	sample in the buffer for more precise sync. Some cleanups.
+
 2004-06-24  Wim Taymans  <wim@fluendo.com>
 
 	* gst/audiorate/gstaudiorate.c: (gst_audiorate_link),

ext/alsa/gstalsa.c

@@ -1203,8 +1203,6 @@ gst_alsa_pcm_wait (GstAlsa * this)
 inline gboolean
 gst_alsa_start (GstAlsa * this)
 {
-  GstClockTime elemnow;
-
   GST_DEBUG ("Setting state to RUNNING");
 
   switch (snd_pcm_state (this->handle)) {
@@ -1215,13 +1213,7 @@ gst_alsa_start (GstAlsa * this)
       ERROR_CHECK (snd_pcm_prepare (this->handle), "error preparing: %s");
     case SND_PCM_STATE_SUSPENDED:
     case SND_PCM_STATE_PREPARED:
-      /* The strategy to recover the timestamps from the xrun is to take the
+      this->captured = 0;
-       * current element time and pretend we just sent all the samples up to
-       * that time. This will result in an offset discontinuity in the next
-       * buffer along with the correct timestamp on that buffer, we only
-       * update the capture timestamps */
-      elemnow = gst_element_get_time (GST_ELEMENT (this));
-      this->captured = gst_alsa_timestamp_to_samples (this, elemnow);
       ERROR_CHECK (snd_pcm_start (this->handle), "error starting playback: %s");
       break;
     case SND_PCM_STATE_PAUSED:
@@ -1254,6 +1246,11 @@ gst_alsa_xrun_recovery (GstAlsa * this)
     GST_ERROR_OBJECT (this, "status error: %s", snd_strerror (err));
 
   if (snd_pcm_status_get_state (status) == SND_PCM_STATE_XRUN) {
+    struct timeval now, diff, tstamp;
+
+    gettimeofday (&now, 0);
+    snd_pcm_status_get_trigger_tstamp (status, &tstamp);
+    timersub (&now, &tstamp, &diff);
 
     /* if we're allowed to recover, ... */
     if (this->autorecover) {
@@ -1269,8 +1266,12 @@ gst_alsa_xrun_recovery (GstAlsa * this)
     }
 
     /* prepare the device again */
-    if ((err = snd_pcm_prepare (this->handle)) < 0) {
+    if ((err = snd_pcm_drop (this->handle)) < 0) {
-      GST_ERROR_OBJECT (this, "prepare error: %s", snd_strerror (err));
+      GST_ERROR_OBJECT (this, "drop error: %s", snd_strerror (err));
+      return FALSE;
+    }
+    if ((err = snd_pcm_drain (this->handle)) < 0) {
+      GST_ERROR_OBJECT (this, "drop error: %s", snd_strerror (err));
       return FALSE;
     }
     if (!gst_alsa_start (this)) {
@@ -1278,8 +1279,10 @@ gst_alsa_xrun_recovery (GstAlsa * this)
           ("Error starting audio after xrun"));
       return FALSE;
     }
-    GST_DEBUG_OBJECT (this, "XRun!!!! pretending we captured %lld samples",
+
-        this->captured);
+    GST_DEBUG_OBJECT (this, "XRun!!!! of at least %.3f msecs, "
+        "pretending we captured %lld samples",
+        diff.tv_sec * 1000 + diff.tv_usec / 1000.0, this->captured);
   } else {
     if (!(gst_alsa_stop_audio (this) && gst_alsa_start_audio (this))) {
       GST_ELEMENT_ERROR (this, RESOURCE, FAILED, (NULL),

ext/alsa/gstalsa.h

@@ -156,7 +156,6 @@ struct _GstAlsa {
 
   /* clocking */
   GstAlsaClock *		clock;		/* our provided clock */
-  GstClockTime			clock_base;
   snd_pcm_uframes_t		played; 	/* samples transmitted since last sync 
 						   This thing actually is our master clock.
 						   We will event insert silent samples or

ext/alsa/gstalsasrc.c

@@ -363,13 +363,6 @@ gst_alsa_src_loop (GstElement * element)
       return;
     }
   }
-  if (this->clock_base == GST_CLOCK_TIME_NONE) {
-    GstClockTime now;
-
-    now = gst_element_get_time (element);
-    this->clock_base = gst_alsa_src_get_time (this);
-    this->captured = gst_alsa_timestamp_to_samples (this, now);
-  }
 
   /* the cast to long is explicitly needed;
    * with avail = -32 and period_size = 100, avail < period_size is false */
@@ -393,8 +386,18 @@ gst_alsa_src_loop (GstElement * element)
 
   {
     gint outsize;
-    GstClockTime outtime, outdur, outreal, outideal;
+    GstClockTime outtime, outdur, outreal, outideal, startalsa, outalsa;
-    gint64 diff;
+    gint64 diff, offset;
+    snd_pcm_status_t *status;
+    struct timeval tstamp;
+    int err;
+
+    snd_pcm_status_alloca (&status);
+
+    if ((err = snd_pcm_status (this->handle, status)) < 0)
+      GST_ERROR_OBJECT (this, "status error: %s", snd_strerror (err));
+
+    offset = this->captured;
 
     /* duration of buffer is just the time of the samples */
     outdur = gst_alsa_samples_to_timestamp (this, copied);
@@ -403,19 +406,25 @@ gst_alsa_src_loop (GstElement * element)
      * what is now in the buffer */
     outreal = gst_element_get_time (GST_ELEMENT (this)) - outdur;
     /* ideal time is counting samples */
-    outideal = gst_alsa_samples_to_timestamp (this, this->captured);
+    outideal = gst_alsa_samples_to_timestamp (this, offset);
+
+    snd_pcm_status_get_trigger_tstamp (status, &tstamp);
+    startalsa = GST_TIMEVAL_TO_TIME (tstamp) - element->base_time;
+    outalsa = startalsa + outideal;
 
     outsize = gst_alsa_samples_to_bytes (this, copied);
     outtime = GST_CLOCK_TIME_NONE;
 
     if (GST_ELEMENT_CLOCK (this)) {
       if (GST_CLOCK (GST_ALSA (this)->clock) == GST_ELEMENT_CLOCK (this)) {
-        outtime = outideal;
+        outtime = outalsa;
         diff = outideal - outreal;
         GST_DEBUG_OBJECT (this, "ideal %lld, real %lld, diff %lld\n", outideal,
             outreal, diff);
+        offset = gst_alsa_timestamp_to_samples (this, outtime);
       } else {
         outtime = outreal;
+        offset = gst_alsa_timestamp_to_samples (this, outtime);
       }
     }
 
@@ -430,8 +439,8 @@ gst_alsa_src_loop (GstElement * element)
 
       GST_BUFFER_TIMESTAMP (src->buf[i]) = outtime;
       GST_BUFFER_DURATION (src->buf[i]) = outdur;
-      GST_BUFFER_OFFSET (src->buf[i]) = this->captured;
+      GST_BUFFER_OFFSET (src->buf[i]) = offset;
-      GST_BUFFER_OFFSET_END (src->buf[i]) = this->captured + copied;
+      GST_BUFFER_OFFSET_END (src->buf[i]) = offset + copied;
 
       buf = src->buf[i];
       src->buf[i] = NULL;