[MPlayer-users] A/V sync problems

[Andre Hinrichs]

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