[MEncoder-users] Re: MEncoder-users Digest, Vol 27, Issue 20

[pfile at pacbell.net]

On Nov 21, 2006, at 3:00 AM, RC wrote:

>
> On Mon, 20 Nov 2006 19:56:04 -0800
> pfile at pacbell.net wrote:
>
>> in this situation, why does mencoder have to insert duplicate frames
>> to maintain the proper framerate? are the extra frames required
>> solely due to rounding error in the frame display time?
>
> Skip/Dupe frames are usually to maintain proper A/V sync.

right. so my question is, if in theory the video still has the same  
length as it did before, why would there be the need to change the A/ 
V sync?
is it only because you can't match the exact required frame display  
time and after a while you need to add or delete a frame because of  
this?

i tried -mc 0 -noskip to avoid duped frames and somewhat predictably  
the audio is drifting against the video. again, i'm trying to  
understand how these release groups manage to transcode atsc shows  
with perfect a/v sync and pretty much perfect decimation. i know they  
are probably not using mencoder, but if virtualdub/etc. can do this  
then there's no reason mencoder cant (given enough code :) it seems  
to me that the only way to fix this is to scale the audio, but i want  
to make sure that's really the case before i go down that rathole.

thanks

rob