[MEncoder-users] Skipped and duplicate frames

The Wanderer inverseparadox at comcast.net
Tue Mar 31 13:05:26 CEST 2009

Peter wrote:

> Andrew Savchenko wrote:
>> If you will have some problems with filters or smooth playback, try
>> -vf softskip, -vf harddup -noskip, -skiplimit. But do not use them
>> carelessly! If everything is fine just let mencoder to do its job.
> Thanks for the answer; I tried all four options, but none removed the
> messages.

Of course not. Those options were not supposed to remove the messages;
they were supposed to fix problems which might be there in spite of or
as a side effect of those messages, and they can have negative side
effects of their own.

The messages just mean "in order to maintain A/V sync, MEncoder had to
duplicate or drop a frame". If you get rid of them without introducing
some other way of maintaining that, audio and video will be out of sync.

> I tried "-nosound" just for the hell of it, and it killed MOST (but
> not all) of them.

That's because, with no audio, there's no need to keep the video in sync
with it.

Just offhand, my guess as to the reason for there being some such
messages left would be that there is a difference in frame rate between
the input and the output, and so frames have to be added or dropped in
order to maintain the same effective playback rate at the new frame

> I have switched to ffmpeg, because for some reason, it does not give
> these errors.

This would be because either it uses a different method for maintaining
A/V sync, or (more likely), it simply doesn't tell you every time it
duplicates or drops a frame - in other words, it's still doing it, it's
just not telling you about it. I don't see how this would be better, but
if you prefer ffmpeg, that's certainly no skin off my nose...

       The Wanderer

Warning: Simply because I argue an issue does not mean I agree with any
side of it.

Secrecy is the beginning of tyranny.

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