baseaudiosink: make drift tolerance configurable

Add drift-tolerance property (defaulting to 20ms) to handle resync after clock
drift or timestamp drift instead of relying on the latency-time value for clock
drift and 500ms for timestamp drift.
Remove warning about discont timestamp and simply resync. The warning is in some
cases not correct and is triggered more frequently now that we lower the
tolerance value.

diff --git a/gst-libs/gst/audio/gstbaseaudiosink.c b/gst-libs/gst/audio/gstbaseaudiosink.c
index 3b0ce56..d84c6f6 100644 (file)
--- a/gst-libs/gst/audio/gstbaseaudiosink.c
+++ b/gst-libs/gst/audio/gstbaseaudiosink.c
@@ -58,6 +58,9 @@ struct _GstBaseAudioSinkPrivate
   GstClockTime eos_time;
 
   gboolean do_time_offset;
+  /* number of microseconds we alow timestamps or clock slaving to drift
+   * before resyncing */
+  guint64 drift_tolerance;
 };
 
 /* BaseAudioSink signals and args */
@@ -85,14 +88,22 @@ enum
 /* FIXME, enable pull mode when clock slaving and trick modes are figured out */
 #define DEFAULT_CAN_ACTIVATE_PULL FALSE
 
+/* when timestamps or clock slaving drift for more than 10ms we resync. This is
+ * a reasonable default */
+#define DEFAULT_DRIFT_TOLERANCE   ((20 * GST_MSECOND) / GST_USECOND)
+
 enum
 {
   PROP_0,
+
   PROP_BUFFER_TIME,
   PROP_LATENCY_TIME,
   PROP_PROVIDE_CLOCK,
   PROP_SLAVE_METHOD,
-  PROP_CAN_ACTIVATE_PULL
+  PROP_CAN_ACTIVATE_PULL,
+  PROP_DRIFT_TOLERANCE,
+
+  PROP_LAST
 };
 
 GType
@@ -208,6 +219,19 @@ gst_base_audio_sink_class_init (GstBaseAudioSinkClass * klass)
       g_param_spec_boolean ("can-activate-pull", "Allow Pull Scheduling",
           "Allow pull-based scheduling", DEFAULT_CAN_ACTIVATE_PULL,
           G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+  /**
+   * GstBaseAudioSink:drift-tolerance
+   *
+   * Controls the amount of time in milliseconds that timestamps or clocks are allowed
+   * to drift before resynchronisation happens.
+   *
+   * Since: 0.10.26
+   */
+  g_object_class_install_property (gobject_class, PROP_DRIFT_TOLERANCE,
+      g_param_spec_int64 ("drift-tolerance", "Drift Tolerance",
+          "Tolerance for timestamp and clock drift in microseconds", 1,
+          G_MAXINT64, DEFAULT_DRIFT_TOLERANCE,
+          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
 
   gstelement_class->change_state =
       GST_DEBUG_FUNCPTR (gst_base_audio_sink_change_state);
@@ -252,6 +276,7 @@ gst_base_audio_sink_init (GstBaseAudioSink * baseaudiosink,
 
   GST_BASE_SINK (baseaudiosink)->can_activate_push = TRUE;
   GST_BASE_SINK (baseaudiosink)->can_activate_pull = DEFAULT_CAN_ACTIVATE_PULL;
+  baseaudiosink->priv->drift_tolerance = DEFAULT_DRIFT_TOLERANCE;
 
   /* install some custom pad_query functions */
   gst_pad_set_query_function (GST_BASE_SINK_PAD (baseaudiosink),
@@ -605,6 +630,9 @@ gst_base_audio_sink_set_property (GObject * object, guint prop_id,
     case PROP_CAN_ACTIVATE_PULL:
       GST_BASE_SINK (sink)->can_activate_pull = g_value_get_boolean (value);
       break;
+    case PROP_DRIFT_TOLERANCE:
+      sink->priv->drift_tolerance = g_value_get_int64 (value);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -635,6 +663,9 @@ gst_base_audio_sink_get_property (GObject * object, guint prop_id,
     case PROP_CAN_ACTIVATE_PULL:
       g_value_set_boolean (value, GST_BASE_SINK (sink)->can_activate_pull);
       break;
+    case PROP_DRIFT_TOLERANCE:
+      g_value_set_int64 (value, sink->priv->drift_tolerance);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -952,8 +983,8 @@ gst_base_audio_sink_skew_slaving (GstBaseAudioSink * sink,
 {
   GstClockTime cinternal, cexternal, crate_num, crate_denom;
   GstClockTime etime, itime;
-  GstClockTimeDiff skew, segtime, segtime2;
-  gint segsamples;
+  GstClockTimeDiff skew, mdrift, mdrift2;
+  gint driftsamples;
   gint64 last_align;
 
   /* get calibration parameters to compensate for offsets */
@@ -990,56 +1021,52 @@ gst_base_audio_sink_skew_slaving (GstBaseAudioSink * sink,
       GST_TIME_FORMAT " skew %" G_GINT64_FORMAT " avg %" G_GINT64_FORMAT,
       GST_TIME_ARGS (itime), GST_TIME_ARGS (etime), skew, sink->priv->avg_skew);
 
-  /* the max drift we allow is the length of a segment */
-  segtime = sink->ringbuffer->spec.latency_time * 1000;
-  segtime2 = segtime / 2;
+  /* the max drift we allow */
+  mdrift = sink->priv->drift_tolerance * 1000;
+  mdrift2 = mdrift / 2;
 
   /* adjust playout pointer based on skew */
-  if (sink->priv->avg_skew > segtime2) {
+  if (sink->priv->avg_skew > mdrift2) {
     /* master is running slower, move internal time forward */
     GST_WARNING_OBJECT (sink,
         "correct clock skew %" G_GINT64_FORMAT " > %" G_GINT64_FORMAT,
-        sink->priv->avg_skew, segtime2);
-    cexternal = cexternal > segtime ? cexternal - segtime : 0;
-    sink->priv->avg_skew -= segtime;
+        sink->priv->avg_skew, mdrift2);
+    cexternal = cexternal > mdrift ? cexternal - mdrift : 0;
+    sink->priv->avg_skew -= mdrift;
 
-    segsamples =
-        sink->ringbuffer->spec.segsize /
-        sink->ringbuffer->spec.bytes_per_sample;
+    driftsamples = (sink->ringbuffer->spec.rate * mdrift) / GST_SECOND;
     last_align = sink->priv->last_align;
 
     /* if we were aligning in the wrong direction or we aligned more than what we
      * will correct, resync */
-    if (last_align < 0 || last_align > segsamples)
+    if (last_align < 0 || last_align > driftsamples)
       sink->next_sample = -1;
 
     GST_DEBUG_OBJECT (sink,
-        "last_align %" G_GINT64_FORMAT " segsamples %u, next %"
-        G_GUINT64_FORMAT, last_align, segsamples, sink->next_sample);
+        "last_align %" G_GINT64_FORMAT " driftsamples %u, next %"
+        G_GUINT64_FORMAT, last_align, driftsamples, sink->next_sample);
 
     gst_clock_set_calibration (sink->provided_clock, cinternal, cexternal,
         crate_num, crate_denom);
-  } else if (sink->priv->avg_skew < -segtime2) {
+  } else if (sink->priv->avg_skew < -mdrift2) {
     /* master is running faster, move external time forwards */
     GST_WARNING_OBJECT (sink,
         "correct clock skew %" G_GINT64_FORMAT " < %" G_GINT64_FORMAT,
-        sink->priv->avg_skew, -segtime2);
-    cexternal += segtime;
-    sink->priv->avg_skew += segtime;
+        sink->priv->avg_skew, -mdrift2);
+    cexternal += mdrift;
+    sink->priv->avg_skew += mdrift;
 
-    segsamples =
-        sink->ringbuffer->spec.segsize /
-        sink->ringbuffer->spec.bytes_per_sample;
+    driftsamples = (sink->ringbuffer->spec.rate * mdrift) / GST_SECOND;
     last_align = sink->priv->last_align;
 
     /* if we were aligning in the wrong direction or we aligned more than what we
      * will correct, resync */
-    if (last_align > 0 || -last_align > segsamples)
+    if (last_align > 0 || -last_align > driftsamples)
       sink->next_sample = -1;
 
     GST_DEBUG_OBJECT (sink,
-        "last_align %" G_GINT64_FORMAT " segsamples %u, next %"
-        G_GUINT64_FORMAT, last_align, segsamples, sink->next_sample);
+        "last_align %" G_GINT64_FORMAT " driftsamples %u, next %"
+        G_GUINT64_FORMAT, last_align, driftsamples, sink->next_sample);
 
     gst_clock_set_calibration (sink->provided_clock, cinternal, cexternal,
         crate_num, crate_denom);
@@ -1248,6 +1275,7 @@ gst_base_audio_sink_render (GstBaseSink * bsink, GstBuffer * buf)
   GstFlowReturn ret;
   GstSegment clip_seg;
   gint64 time_offset;
+  gint64 maxdrift;
 
   sink = GST_BASE_AUDIO_SINK (bsink);
 
@@ -1482,26 +1510,20 @@ gst_base_audio_sink_render (GstBaseSink * bsink, GstBuffer * buf)
   else
     diff = sink->next_sample - sample_offset;
 
-  /* we tollerate half a second diff before we start resyncing. This
-   * should be enough to compensate for various rounding errors in the timestamp
-   * and sample offset position. We always resync if we got a discont anyway and
-   * non-discont should be aligned by definition. */
-  if (G_LIKELY (diff < ringbuf->spec.rate / DIFF_TOLERANCE)) {
+  /* calculate the max allowed drift in units of samples. By default this is
+   * 20ms and should be anough to compensate for timestamp rounding errors. */
+  maxdrift = (ringbuf->spec.rate * sink->priv->drift_tolerance) / GST_MSECOND;
+
+  if (G_LIKELY (diff < maxdrift)) {
     /* calc align with previous sample */
     align = sink->next_sample - sample_offset;
     GST_DEBUG_OBJECT (sink,
-        "align with prev sample, ABS (%" G_GINT64_FORMAT ") < %d", align,
-        ringbuf->spec.rate / DIFF_TOLERANCE);
+        "align with prev sample, ABS (%" G_GINT64_FORMAT ") < %"
+        G_GINT64_FORMAT, align, maxdrift);
   } else {
-    /* bring sample diff to seconds for error message */
-    diff = gst_util_uint64_scale_int (diff, GST_SECOND, ringbuf->spec.rate);
-    /* timestamps drifted apart from previous samples too much, we need to
-     * resync. We log this as an element warning. */
-    GST_ELEMENT_WARNING (sink, CORE, CLOCK,
-        ("Compensating for audio synchronisation problems"),
-        ("Unexpected discontinuity in audio timestamps of more "
-            "than half a second (%" GST_TIME_FORMAT "), resyncing",
-            GST_TIME_ARGS (diff)));
+    GST_DEBUG_OBJECT (sink,
+        "discont timestamp (%" G_GINT64_FORMAT ") >= %" G_GINT64_FORMAT, diff,
+        maxdrift);
     align = 0;
   }
   sink->priv->last_align = align;