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Old 05-09-07, 05:09 PM   #4
Carina Denkmann
Registered User
Join Date: May 2007
Posts: 2
Default Re: possible sync issue with 1080i content @ 1080i


It is not your TV that is unusal. The TV should adapt to any speed the
video card supplies (within the tolerated range).

The problem is that there is no internal communication in mplayer regarding synchronization with the video card.

For smooth playback to work, either
- the video card would have to swap frames when requested to do so
by mplayer (kind of internal genlocking), which is not possible with
nvidia hardware (s.o. correct me if I'm wrong), or
- mplayer would have to listen to Vertical Retrace Interrupts from the
nvidia hardware, and adjust its playback speed, which it doesn't do.
Instead, it listens to the audio hardware, to provide gapless audio

I don't know who is the culprit for the inaccuracy on my system, but
either of the quartzes of the video card, audio card, or mainboard has
a tolerance of more then 0.2% (which is 1 frame in about 20 seconds,
similar to your experience, if my math is correct).

The problem gets worse when displaying live feeds, such as DVB
streams, because both audio and video hardware would have to be
sync'ed to the input speed. If you don't force mplayer to play
SLIGHTLY slower than input speed, you will sooner or later run into
buffer underruns.

Complicated topic. The best solution is to use a de-interlacer with full
progressive frame interpolation, so out-of-sync fields don't show up as
jagged movements. But the -vf=yadif filter is too slow on my machine
for 1080i content, I use it for 576i (PAL) content though.
Carina Denkmann is offline   Reply With Quote