gst/matroska/matroska-demux.c: Don't calculate the default duration of a frame from...

gst/matroska/matroska-demux.c: Don't calculate the default duration of a frame from the audio sampling rate. This onl...

Original commit message from CVS:
* gst/matroska/matroska-demux.c: (gst_matroska_demux_add_stream):
Don't calculate the default duration of a frame from the audio sampling
rate. This only works for raw audio if every frame contains a single
sample and results in broken buffer durations for other formats
if no specified default duration is given or the blocks have no
duration. Fixes bug #548831.