[MPlayer-users] mencoder a-v sync and DVDs (again)

[christopher j bottaro]

this is hard for me to explain, but lemmie try.  i wrote a perl script that 
examines mencoder's output and counts consective frames who's abs(A-V) value 
is greater than 0.03.

so consider the following mencoder output:
Pos:5662.8s 135773f (81%)   5fps Trem:  91min 750mb  A-V:0.023 [811:93]]]
Pos:5662.8s 135774f (81%)   5fps Trem:  91min 750mb  A-V:0.013 [811:93]]]
Pos:5662.8s 135775f (81%)   5fps Trem:  91min 750mb  A-V:0.033 [811:93]]]
Pos:5662.8s 135776f (81%)   5fps Trem:  91min 750mb  A-V:0.043 [811:93]]]
Pos:5662.8s 135777f (81%)   5fps Trem:  91min 750mb  A-V:0.043 [811:93]]]
Pos:5662.8s 135778f (81%)   5fps Trem:  91min 750mb  A-V:0.013 [811:93]]]

the perl script would spit out something like:
frames 135775-135777, count 3, avg (0.033+0.043+0.043)/3
where the avg would the value of that expression.

well, i've noticed some weirdness.  if i use a recent version of mencoder, 
then pretty much the whole thing would be outta sync...like frames 
100-end_frame, and when playing the divx, the audio would be noticibly off.

if i use the dec 10, 2002 snapshot of mencoder, i still get lots and lots of 
chunks of frames that are off (by pretty high avgs also, like > 0.05), but 
the resulting divx would playback fine........

i honesty don't know if this means anything significant, its just something 
i've noticed.

another weird thing i've noticed is that if i use mplayer -dvd 1 (dec 10th 
snapshot) to play certain dvds, the audio would be waaaay off.  but if i 
encode the same dvd to divx using mencoder, the audio isn't off at all in the 
resulting divx...

thanks for looking into this, i think mplayer/mencoder is great, i just wish i 
could upgrade from the dec 10th snapshot...=)

-- christopher

P.S.  here is some output from my script.  note that the divx that was created 
from this plays back with no AV sync problems...despite all the "AV desync" 
messages my script spits out...

first pass
mencoder -oac mp3lame -lameopts abr:br=96 -ovc frameno -o frameno.avi -ofps 
23.976 -dvd 1 -aid 128
 0% done,    0 mins remaining
AV desync detected: range 11-38, count 27, avg 0.0540740740740741
 0% done,    0 mins remaining
AV desync detected: range 56-61, count 5, avg 0.0384
 5% done,   12 mins remaining
AV desync detected: range 85-9155, count 9070, avg 0.0483592061742018
 6% done,   11 mins remaining
AV desync detected: range 9158-10872, count 1714, avg 0.0480793465577597
11% done,   11 mins remaining
AV desync detected: range 10876-18885, count 8009, avg 0.0478329379448131
13% done,   11 mins remaining
AV desync detected: range 18899-21515, count 2616, avg 0.047663226299695
17% done,   10 mins remaining
AV desync detected: range 21529-26598, count 5069, avg 0.0475241665022688
21% done,    9 mins remaining
AV desync detected: range 26600-32936, count 6336, avg 0.0472250631313132
27% done,    9 mins remaining
AV desync detected: range 32939-42492, count 9553, avg 0.0467689730974575
30% done,    8 mins remaining
AV desync detected: range 42509-47392, count 4883, avg 0.0631484742985865
34% done,    8 mins remaining
AV desync detected: range 47403-53501, count 6098, avg 0.0632100688750407
72% done,    3 mins remaining
AV desync detected: range 111107-111110, count 3, avg 0.032
75% done,    3 mins remaining
AV desync detected: range 114361-114374, count 13, avg 0.0418461538461538
100% done,    0 mins remaining
AV desync detected: range 155903-155908, count 6, avg 0.04
100% done, 0 mins remaining
this pass recommended a vbitrate of 801

On Tuesday 11 February 2003 01:58 am, Corey Hickey wrote:
> No, the problem is that when mencoding, a typical output status line
> looks like this:
> Pos:5662.8s 135773f (81%)   5fps Trem:  91min 750mb  A-V:0.073 [811:93]]]
>
> Where A-V is constantly near a certain value somewhere between 0.000 and
> 0.100 (but that value is always between +- 0.030 and +- 0.080). Within a
> single movie, the A-V drifts around by about 0.015 (which isn't a
> problem) but is always consistantly near that certain value. For
> instance, as I watch the above movie get encoded, it is always between
> 0.065 and 0.075, which is definitely perceptible. Playing the encoded
> movie with -delay 0.070 looks just fine.
>
> Different movies have different values about which the A-V centers. Some
> are 0.030, some are 0.080, etc.
>
> Sorry, I have a hard time explaining this. Christopher might be able
> to describe the problem better. Also, take a look here:
> http://www.mplayerhq.hu/pipermail/mplayer-users/2003-February/029156.html
>
> Thanks again,
> Corey
>
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