[MEncoder-users] Skipping frame! and duplicate frame(s)! problems

[Corey Hickey]

Jonathan wrote:
>>>  While trying to encode some of my DVDs for portability purposes
>>>I've run into problems with a lot of skipped and duplicated frames.
>>
>>
>>I see that you've got a few duplicate frames, and skiped frames,
>>but I don't see a problem.
> 
> 
> In the areas where this happens the output is horribly 
> interlaced/telecined and farther into the source it starts skipping 
> frames every 5-10 frames and went on doing so for over 500 frames before 
> I killed the encode.
> 

Try using filmdint. In my experience it does better than pullup (and
ivtc) with regard to skipped frames in telecined video. If your video
isn't telecined, though, the skipping is pretty much unavoidable.

NTSC DVD video can have either 24000/1001 fps or 30000/1001, and is
allowed to switch at any time. This usually happens during the DVD
mastering process when sections of video with different framerates are
spliced together.

For a television set, the DVD player is supposed to telecine the
24000/1001 parts so the the entire video is 60000/1001 fields per second.

For a computer, the video can be displayed at either framerate,
30000/1001 fps material looks ugly ("combing"/"mice teeth") because it's
either interlaced or has been telecined already.

When encoding a mixed-framerate dvd to a single-framerate container such
as avi, 30000/1001 fps video must be reduced to 24000/1001 somehow.
Pullup and filmdint inverse-telecine telecined video, thus reducing the
framerate as desired. If the 30000/1001 fps material is not telecined,
however, the only way to get 24000/1001 fps out of it is by skipping a
frame now and then. Mencoder can't just slow it down because then the
video would lag behind the audio.

>>mencoder doesn't really change the framerate per-se, it's just informing
>>you that the framerate of the source video has changed.
>>
> 
> Is that hardcoded into the video stream or is it just something mencoder 
> figures out?
> 

Yes, the different fps values are within the video stream. When
mencoder/mplayer notices a change it prints a message.

> Of course I feel rather stupid for not checking the effects on the 
> actual playback before sending an email but I guess thats what I get for 
> sending mail when tired :P  I still have not checked the effects on 
> encoded material but thats partly a time issue, H.264 is *really* nice 
> but a bit slow!

Just for fun, try out snow. On my tests, it retains considerably more
detail than x264. Snow is not finished yet, but I like it already.

-Corey