[mythtv-users] MPEG4 NUV to AVI (Solved?)

Steve Smith st3v3.sm1th at gmail.com
Wed Jan 9 14:40:00 UTC 2008


After much experimentation and many CPU hours I think I've found a formula
that works for
converting mpeg4 nuv files e.g. transcoded from mpeg2 originals to save
space into MPEG4 (DIVX) avi files WITHOUT reencoding.

(If you don't mind re-encoding the video, and the attendant time and loss of
quality, then "nuvexport" as recommended by many on this list is the easiest
solution I've found).

My magic spell is:

     1) Use    nuv2avi -i FILE.nuv -o OUT1.avi
      to get the mpeg4 video and audio from the nuv into an avi file.

  Unfortunately I found that after this process the sound is corrupted when
I play in mplayer and vlc on Windows (Myth's Internal player has no problems

       Split off the sound from OUT1.avi and re-multiplex....
             ffmpeg -i OUT1.avi -vn -acodec copy OUT.mp3
             ffmpeg -i OUT1.avi -map 0:0 -i OUT.mp3 -map 1:0 -acodec copy
-vcodec copy   FINAL.avi

This didn't always work though so you could try:

      METHOD B
           nuvexport --mode mp3 -i FILE.nuv           (Use nuvexport to get
the soundtrack via mythtranscode)
           ffmpeg -i OUT1.avi -map 0:0 -i NUVEXPORTOUTPUT.mp3 -map 1:0
-acodec copy -vcodec copy   FINAL.avi

       METHOD A uses the original soundtrack in the NUV and just re
multiplexes it.
       METHOD B gets mythtranscode to "play" the file into lame to reencode
it into mp3 again. I suspect this might have been needed because the files I
used it on were transcoded with an audio bit rate of 32000 rather than
48000. I'm not sure if nuv2avi was able to handle this.

(For links to nuv2avi search the mail archives).


Aspect Ratio: For 4:3 files e.g. from a PVR-150 this process works well.
       For other aspect ratios it all depends on what you are using to play
the file back.
Software players like myth and mplayer are very flexible in how they display
the avi.
Hardware players usually are not, this can mean that in order to get the
picture right on your TV you need to reencode to the right size. It's
probably easier to use nuvexport for this.

I hope this helps someone in the future....

and in future I'll probably be transcoding into avi in the first place...


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