Sync problem with mpeg4

[Radivoje Jovanovic]

I have following pipeline:
gst-launch-0.10 filesrc location=my_movie.mp4 ! qtdemux name=t ! queue  !
my_mpeg4_dec ! my_video_sink  t. ! queue ! faad ! alsasink.
I am using the same pipeline to play mpeg4 and h264 videos (different
decoder for h264). H264 works just fine but mpeg4 has sync problems. The
video is as twice as fast as it should be. If I provide sync=false into
my_mpeg4_dec line it all works fine but I do not want to do it this way. I
just read in the documentation that:

"Sometimes it is a parser element the one that knows the time, for instance
if a pipeline contains a
filesrc element connected to a MPEG decoder element, the former is the one
that knows the time of
each sample, because the knowledge of when to play each sample is embedded
in the MPEG format.
In this case this element will be regarded as the source element for this
discussion."

I am not sure how does ALSA gets the time stamp when it cannot see mpeg4
directly? Is mpeg4 supposed to update global clock upstream so ALSA can see
it or what?
Cheers,
Ogi
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