[MPlayer-users] A/V sync problems
Andre Hinrichs
andre at gandalf.andre-hinrichs.de
Wed Oct 30 13:48:06 CET 2002
Hi!
I'm just saving some diskspace and want to convert several MPGs to DIVX.
In some cases I discovered some strange problems which I can not explain.
Example:
An MPG which is about 43:30 minutes long. Framerate is 25.0
I've made four tests with one or three passes and setting the framerate
explicitely or not.
Test 1: One pass encoding without fps
mencoder -forceidx -oac copy -ovc lavc -lavcopts vcodec=mpeg4:vhq:vbitrate=400
-o out.avi in.mpg
Result:
When simply playing the movie after 100 seconds the state line looks as
follows:
A: 103,1 V: 103,1 A-V: -0,000 ct: 0,010 2579/2579 9% 9% 1,3% 0 0 0%
OK! That's fine. But now look, what happens if I step 10 seconds back and play
it until the movie is at the same position:
A: 102,9 V: 102,9 A-V: -0,011 ct: 0,682 2574/2574 8% 9% 1,2% 0 0 0%
Shit! That's not OK. The A/V drift is 0,682 seconds. The drift falls back to
zero immediately after stepping but slowly increasing after that to the value
shown above. Here is the state line immediately after stepping:
A: 102,2 V: 101,6 A-V: 0,587 ct: 0,064 2542/2542 10% 9% 1,4% 0 0 0%
Test 2: Three pass encoding without fps
Test 3: One pass encoding without fps
Test 4: Three pass encoding with fps
All these tests have nearly the same results:
Simply playing is OK. Stepping through the movie results in the following:
A: 103,0 V: 103,0 A-V: 0,020 ct: 0,119 2575/2575 8% 9% 1,8% 0 0 0%
That's better as the one pass result, but still not OK.
Playing the original MPG results in the following state lines:
With stepping:
A: 103,2 V: 103,2 A-V: -0,003 ct: 0,081 451/451 7% 9% 1,4% 0 0 0%
Without stepping:
A: 103,3 V: 103,3 A-V: 0,016 ct: -0,017 2569/2569 7% 9% 3,7% 13 0 0%
Can I do something, that I can step through the movie without loosing the A/V
sync?
Oh yes, I of course do use the latest version MPlayer-0.90pre9
Greetings
Andre
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