[MEncoder-users] -ss and -endpos cutting creates very visible h264 artifacts

[Marc MERLIN]

On Tue, Mar 02, 2010 at 07:54:36AM +0100, Martijn van Beurden wrote:
> >mkvmerge -o out.mkv 491_Keystone2_treerun_fall.avi 
> >mencoder -ss 0:1:20 -endpos 0:0:30 -oac copy -ovc copy out.mkv -o out2.mkv 
> >
> >And it's the same problem, out2.mkv still seems to be missing a keyframe
> >and the video only looks ok after about 10 seconds.
>
> I think he meant copy the whole video (without ss and endpos) to another 
> container, which rebuilds the index, 

isn't it what I did with the first mkvmerge line?

> and then trying to transcode with ss and endpos.                          

I thought this is what I did too :)

> You could try it with an EDL and -hr-edl-seek too, as 
> that decodes the whole video, but encodes just the parts you need. As 
> this looks like a decode problem, that should work.

Aaah, another great option I knew nothing about. Thanks :)

Actually a simple
mencoder -edl cuts -oac copy -ovc copy 491_Keystone2_treerun_fall.avi -o out3.avi
worked fine

Interestingly the man page says
       -hr-edl-seek
              Use  a  more precise, but much slower method for skipping areas.
              Areas marked for skipping  are  not  seeked  over,  instead  all
              frames  are  decoded, but only the necessary frames are encoded.
              This allows starting at non-keyframe boundaries.
              NOTE: Not guaranteed to work right with '-ovc copy'.

I tried without it and it 'just worked', but it seems to work fine with it too.

Veel bedankt,
Marc
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