[MPlayer-users] AV-sync trouble/ RT streaming

Rainer Weikusat weikusat at students.uni-mainz.de
Sun Mar 23 16:04:59 CET 2003


I've written a small RFC2250 implementation to receive MPEG-ES (video
& audio) RTP-sessions and output their contents mulitplexed together
as PES-stream (to be used for some kind of RT-streaming in some
distant future. Don't tell me about live.com, I am targetting *small*
pentium-class systems and the data copies alone would kill
me). Currently, I am using mplayer (0.90rc5) as 'test-environment',
which works very nicely for an unpredictable period of time until the
player badly looses A-V-sync and will not even come close to it again
if dropping each & every videoframe it received (the audio-display-PTS
keeps raising rapidly while the other advances considerably slower. If
the video-PTS is ahead, a different problem occurs, but that doesn't
matter for the moment).

What (seemingly) happens is that the player processes audio in large
batches of several frames with different PTS, while it only reads one
video frame per batch, even if it already received all frames up to
the audio 'display pts'. This could be related to gaps (lost frames)
in the video stream, which might cause audio getting ahead of video
once and with this getting progressively worse, because the video
frames that should be displayed alongside it keep sitting in the queue
until they are also late (this is a guess, though).

Any ideas (references to particular parts of the source included)?

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