[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

A Ashley <bugzilla> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
 Attachment #295549|none                        |needs-work
             status|                            |

--- Comment #19 from A Ashley <bugzilla at ashley-family.net> 2015-02-03 11:04:38 UTC ---
Review of attachment 295549:
 --> (https://bugzilla.gnome.org/review?bug=742979&attachment=295549)

> 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.

> 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?

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