[MPlayer-users] Many problems editing .AVI files

[Hugues Talbot]

Hello everybody,


First thanks to the mplayer/mencoder developers, this is currently the
most reliable tool for video on Linux! This e-mail is not so much a 
series of bug reports as a number of problems I've encountered and 
don't know how to deal with.

Here's what I want to do:

1- Capture TV shows
2- Edit commercials/TV adverts out of them.
3- Encode to some version of DivX

For (1) I've tried a great number of tools and use either vcr or nuvrec
(NuppelVideo)

For (3) I currently use mencoder, I found transcode much less reliable
on my setting (the sound in particular is horrible, probably a driver
problem).

I don't know what to do do for (2). Here's what I've tried with little
success:

(2)a : encode big .nuv files to some version of divx as avi files
(2)b : use the mencoder -ss and -endpos switches to obtain a great
many small .avi files which are commercial free.
(2)c : try several tricks to concatenate the small .avi files into
a larger one:

  (2)c-i   : avimerge -o big.avi -i small1.avi small2.avi etc
  (2)c-ii  : avicat small1.avi small2.avi ...  -o big.avi
  (2)c-iii : cat small1.avi small2.avi ... > temp.avi ; \
             mencoder -idx temp.avi -ovc copy -oac copy -forceidx  -o big.avi

OK, so the problems are:

 (A) mencoder can't cope with a 3-pass encoding from a .nuv file ; it
     seems to extract the audio fine but then crashes immediately at
     the first pass. However a 2-pass encoding works (one just has
     to encode the audio twice, not a big worry). Not a show-stopper.

 (B) The results from using the -ss and -endpos switch with mencoder 
     are not great. In particular when using -ss the resulting .avi
     shows some video artifacts for the first couple of seconds (probably
     because a clean reference frame was cut off). Maybe -ss should
     only allow cutting at the nearest safe points in the source .avi file? 
     Annoying but not a big problem.

 (C) The resulting small commercial-free .avi files can't be pasted 
     together without losing the audio sync by any of the methods
     outlined above (2)c-i to (2)c-iii. The first portion plays
     fine but the parts after the merge play increasingly worse,
     up to several seconds delay between A and V. I suspect this might
     be because -ss does not cut at a `safe' point in the .avi, if
     such a thing exists. BTW I can never fix the audio delay in
     mplayer with +/-. That never works for me (somehow mplayer seems
     to forget the correction after a few seconds, and anyway this
     is not a workable solution).


So at the moment I play my small files with `mplayer small*.avi' but this
is not great. In particular if I play full-screen with dga, say, mplayer
revert to X in between files and then reset the full-screen play again:
i.e two resolution changes per file, which is not nice. Even if I don't
play full screen, mplayer resets the window to the top-left corner of
the screen for each file.

I realize I can play  `cat small*.avi | mplayer -' which solves the
resolution switch problem but then I can't seek... I like to be able
to replay a bit of dialog from time to time.


Anyway, I wonder if someone has a solution for any of the outlined problems,
anything would be helpfull, thanks for reading so far!


PS: a tiny last point: I find the -endpos switch confusing: it indicates
a duration, not a position (the man page is clear on that). maybe
change it so -dur or -length of something like that.

Cheers.


--------
Hugues Talbot, CSIRO Mathematical & Information Sciences
Locked Bag 17, Building E6B, Macquarie University  North Ryde  
NSW  2113  Australia           Ph: 61 2 9325 3208 Fax: 61 2 9325 3200

Just because you do not take an interest in politics doesn't mean 
politics won't take an interest in you. -- Pericles, 430 B.C.