[Bug 742979] adaptivedemux: Adaptive bitrate algorithm does not react fast enough to declining bitrate

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=742979
  GStreamer | gst-plugins-bad | git master

--- Comment #21 from Mathieu Duponchelle <mduponchelle1 at gmail.com> 2015-02-03 11:41:14 UTC ---
(In reply to comment #19)
> Review of attachment 295549 [details]:
> 
> > static void
> >+gst_adaptive_demux_set_property (GObject * object, guint prop_id,
> >+    const GValue * value, GParamSpec * pspec)
> >+{
> >+  GstAdaptiveDemux *demux = GST_ADAPTIVE_DEMUX (object);
> >+
> >+  switch (prop_id) {
> >+    case PROP_LOOKBACK_FRAGMENTS:
> >+      demux->num_lookback_fragments = g_value_get_uint (value);
> >+      break;
> >+    default:
> >+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
> >+      break;
> >+  }
> >+}
> >+
> 
> Probably should check if demux has already been started. Given the current
> code, increasing the buffer size after start will cause a buffer overflow.
> I think that either the property should not be changeable after start, or the
> buffer needs to re-allocated if the property is changed.

The propery is indeed declared as CONSTRUCT_ONLY

> > static guint64
> >-gst_adaptive_demux_stream_update_current_bitrate (GstAdaptiveDemuxStream *
> >-    stream)
> >+_update_average_bitrate (GstAdaptiveDemux * demux,
> >+    GstAdaptiveDemuxStream * stream, guint64 new_bitrate)
> >+{
> >+  gint index = stream->moving_index % demux->num_lookback_fragments;
> >+
> >+  stream->moving_bitrate -= stream->fragment_bitrates[index];
> >+  stream->fragment_bitrates[index] = new_bitrate;
> >+  stream->moving_bitrate += new_bitrate;
> >+
> >+  stream->moving_index += 1;
> >+
> >+  if (stream->moving_index > demux->num_lookback_fragments)
> >+    return stream->moving_bitrate / demux->num_lookback_fragments;
> >+  return stream->moving_bitrate / stream->moving_index;
> >+}
> 
> Should this be reset after a seek?

I would think this info is still significant after a seek.

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