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baseaudiosink: don't allow aligning behind the read-segment

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Given a large enough drift-tolerance, one could end up in a situation
where one would keep aligning the written buffers behind the current
read-segment position. The result for the reader would be complete
silence, possible preceded by very choppy audio.

By checking the available headroom, one can determine if there is
room to do alignment, or if one should resort to a resync instead to get
the pointers back on track.

Also refactor the alignment-logic out of the render function for cleaner
code.
This commit is contained in:
Havard Graff 2011-02-08 18:27:43 +01:00 committed by Sebastian Dröge
parent 12513a9537
commit 588ac0ae6f
1 changed files with 51 additions and 24 deletions
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75
gst-libs/gst/audio/gstbaseaudiosink.c
View file

@ -1319,6 +1319,56 @@ flushing:
}
}
static gint64
gst_base_audio_sink_get_alignment (GstBaseAudioSink * sink, GstClockTime sample_offset)
{
GstRingBuffer *ringbuf = sink->ringbuffer;
gint64 align;
gint64 diff;
gint64 maxdrift;
gint segdone = g_atomic_int_get (&ringbuf->segdone) - ringbuf->segbase;
gint64 samples_done = segdone * ringbuf->samples_per_seg;
gint64 headroom = sample_offset - samples_done;
gboolean allow_align = TRUE;
/* now try to align the sample to the previous one, first see how big the
* difference is. */
if (sample_offset >= sink->next_sample)
diff = sample_offset - sink->next_sample;
else
diff = sink->next_sample - sample_offset;
/* 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;
/* calc align with previous sample */
align = sink->next_sample - sample_offset;
/* don't align if it means writing behind the read-segment */
if (diff > headroom && align < 0)
allow_align = FALSE;
if (G_LIKELY (diff < maxdrift && allow_align)) {
GST_DEBUG_OBJECT (sink,
"align with prev sample, ABS (%" G_GINT64_FORMAT ") < %"
G_GINT64_FORMAT, align, maxdrift);
} else {
/* calculate sample diff in seconds for error message */
gint64 diff_s = 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_WARNING_OBJECT (sink,
"Unexpected discontinuity in audio timestamps of "
"%s%" GST_TIME_FORMAT ", resyncing",
sample_offset > sink->next_sample ? "+" : "-",
GST_TIME_ARGS (diff_s));
align = 0;
}
return align;
}
static GstFlowReturn
gst_base_audio_sink_render (GstBaseSink * bsink, GstBuffer * buf)
{
@ -1340,7 +1390,6 @@ 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);
@ -1574,29 +1623,7 @@ gst_base_audio_sink_render (GstBaseSink * bsink, GstBuffer * buf)
goto no_align;
}
/* now try to align the sample to the previous one, first see how big the
* difference is. */
if (sample_offset >= sink->next_sample)
diff = sample_offset - sink->next_sample;
else
diff = sink->next_sample - sample_offset;
/* 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 ") < %"
G_GINT64_FORMAT, align, maxdrift);
} else {
GST_DEBUG_OBJECT (sink,
"discont timestamp (%" G_GINT64_FORMAT ") >= %" G_GINT64_FORMAT, diff,
maxdrift);
align = 0;
}
align = gst_base_audio_sink_get_alignment (sink, sample_offset);
sink->priv->last_align = align;
/* apply alignment */