[MPlayer-users] Digitizing VHS tapes with mencoder

[Josef Wolf]

On Sat, Apr 24, 2010 at 09:50:38PM -0700, RC wrote:
> On Sat, 24 Apr 2010 13:48:49 +0200
> Josef Wolf <jw at raven.inka.de> wrote:
> 
> > So now I capture with
> > 
> >   sudo ionice -c 1 nice -n -20 mencoder tv:// -tv
> >   driver=v4l2:mjpeg:width=768:height=576:input=1:fps=50:quality=100:n
> >   orm=pal:buffersize=100:forceaudio:alsa:adevice=hw.0,0,0:amode=1:imm
> >   ediatemode=0:outfmt=yuy2 -forceidx -oac copy -ovc copy -of avi
> >   -endpos 4:10:00 -o outfile.avi
> 
> Does yv12 work in place of yuy2? It should save you some space.

Yeah, this reduces to about 1GB per minute.

> Other than that, you can reduce quality if necessary, but you're pretty well
> at the mercy of the hardware...

I'd rather not reduce quality. Maybe there's a way to encode lossless? AFAIK,
the above command stores every frame as a full mjpeg picture. So simply
convert them to P/I-frame sequences without further encoding techniques
should save some space without reducing quality. Any hints?

Then there's the problem that -ss option don't work if combined with the
-forceidx option. So I tried to "mencoder -ovc copy -oac copy -forceidx ..."
after the encoding pass. But this gives me a broken file. When I jump
backwards or forwards with mplayer in this file, I get this error message:

  number of reference frames exceeds max (probably corrupt input), discarding one

and the video is garbled as if there are no key frames at all in it.
Any ideas on that?