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