[mythtv-users] transcoding perfect dvd rips to xvid

Mike Schiller mdschiller.mythtv at gmail.com
Wed Feb 21 02:04:06 UTC 2007


Thanks for your help.  I tried the command...

date; \
mencoder dvdRip.vob -ovc lavc -lavcopts vcodec=mpeg4:vpass=1 \
       -oac copy -o /dev/null; \
mencoder dvdRip.vob -ovc lavc -lavcopts \
       vcodec=mpeg4:mbd=2:trell:vpass=2 -oac copy -o dvdRip.avi; \
date

... and got good looking video and audio.  Unfortunately, I didn't
include the autoaspect=1 flag, so I got 3:2 letterbox as my output.
I'm re-running the encoding with the flag.  Is it safe to assume that
I need the autoaspect flag for both passes?  The command line I'm
using is....

date; \
mencoder dvdRip.vob -ovc lavc -lavcopts vcodec=mpeg4:vpass=1:autoaspect=1 \
       -oac copy -o /dev/null; \
mencoder dvdRip.vob -ovc lavc -lavcopts \
       vcodec=mpeg4:mbd=2:trell:vpass=2:autoaspect=1 -oac copy -o dvdRip.avi; \
date

There does seem to be one glitch in the process.  Both with and
without the autoaspect flag, every 4 frames I get an error:

   1 duplicate frame(s)!

Is this normal?

Thanks,
Mike


On 2/19/07, David Brodbeck <gull at gull.us> wrote:
> Mike Schiller wrote:
> > Thanks, David.  I'm definitely open to non-ffmpeg solutions, I guess I
> > shouldn't have been so restrictive in my posting.  Your mencoder
> > solution look like an excellent solution to my problem.  I do have a
> > couple of quick follow-up questions:
> >
> > I take it that I just replace dvd://2 with the input file name?
> >
>
> Yup.  If you find you're not happy with the quality, you might want to
> take a look at the stuff in this section:
> http://www.mplayerhq.hu/DOCS/HTML/en/encoding-guide.html
> There's a *lot* of info there about how to get the best quality when
> transcoding DVDs, including deinterlacing and inverse telecine.
>
> Oh, I just remembered...for transcoding MythTV files, I found I needed
> to add "autoaspect" to the list of vcodec options.  This preserves the
> aspect ratio encoded in the original file.
>
> > Since it can handle anything mplayer can play, then is it safe to
> > assume that it will automatically handle the number of input audio
> > channels properly?
> >
>
> The first example they give copies the existing audio stream without
> making any changes.  That's what "-oac copy" means.  So if you start
> with (say) 5.1 AC3 audio, that's what you'll get in the final file, as
> well.
>
> > Does encoding the audio to MP3 preserve the number of input audio channels?
> >
>
> That I'm not sure about.  I haven't tried MP3 encoding.  I like keeping
> the AC3 audio around in case I ever switch to using SPDIF audio out.
> Also, MP3 audio seems to carry with it a higher risk that the video and
> audio will get out of sync.
>
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