[mythtv-users] Cutting commercials without expensive transcoding

[James L. Paul]

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On Saturday 13 March 2004 6:23 pm, Anthony wrote:
> Is there anyway to pass a cutlist to avidemux2? I have looked at the
> commandline parameters in the docs but it doesn't appear that there is a
> way?

I don't think so, but avidemux2 does have a commandline interface. It should 
be possible to script specific cuts from a script that reads a cutfile and 
invokes avidemux2 for each cut. I think somebody on this list actually had 
that automated, although if I remember correctly it was unwieldy because 
avidemux2 doesn't provide any way to hide the GUI when called from a 
commandline.

FWIW, I haven't tried it.

> --Anthony
>
> > -----Original Message-----
> > From: mythtv-users-bounces at mythtv.org [mailto:mythtv-users-
> > bounces at mythtv.org] On Behalf Of James L. Paul
> > Sent: Saturday, March 13, 2004 1:12 PM
> > To: Discussion about mythtv
> > Subject: Re: [mythtv-users] Cutting commercials without expensive
> > transcoding
> >
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> > On Thursday 11 March 2004 6:22 pm, Len Reed wrote:
> > > Hi,
> > >
> > > I'm no video expert, so maybe I misunderstand the problem.  Or maybe
> > > I'm missing a simple answer that's already there.
> > >
> > > I have a PVR250, so my .nuv files are mpeg2 with video and audio
> > > multiplexed in them.  After I've marked the commercials (i.e., started
> > > with myth's guesses and tweaked them using the built-in cut editor),
> > > I'd like to do two things:
> > >
> > > 1. Remove the dreaded commercials in order to shrink the file.
> >
> > I also use PVR250 output. I still remove commecials manually with
> > avidemux2
> > when I want to archive to CVD or DVD. I only cut on keyframe boundaries.
> >
> > > and optionally
> > >
> > > 2. convert to a plain mpeg2 for use in burning a DVD.  (The issue here
> > > may be my poor DVD authoring s/w.  mplayer plays the unmolested .nuv
> > > files.  OTOH, mplayer will play almost anything.)
> >
> > This has been discussed on this list, with specific steps. It's very
> > easy. The
> > output of the PVR250 will work fine on a DVD with no transcoding. I just
> > cut
> > out the commercials with avidemux2, remultiplex with DVD nav headers and
> > pass
> > it to dvdauthor. I have burned many DVDs and CVDs from non-transcoded
> > PVR250
> > output captured from my MythTV box. The video format is fine, the audio
> > format seems to work on most DVD players also. (Technically, I think
> > standard
> > players aren't required to play MPEG audio is AC3 audio isn't present,
> > but I
> > haven't heard of a case yet where it doesn't work anyway.)
> >
> > > I've tried using various methods to accomplish #1: the built-in
> > > transcoding (press 'x'), nuvexport, etc.  The problem with all of them
> > > is that they do time-consuming transcoding.
> >
> > I'm not aware that anybody has a fully automated process for this from
> > within
> > myth. There are people working on it though.
> >
> > > I don't want to change the bit rate or the format, I just want to lift
> > > the parts that have the actual program, leaving behind the ads.  It
> > > seems that that should take, in theory, about as much time as it takes
> > > to read the parts of the original file that I care about and write them
> > > out.  No serious computation, though maybe a bit of knitting around the
> > > edges.
> >
> > The basic key to this is to capture in a DVD-compliant stream format in
> > the
> > first place. You should only need to transcode if your captured stream is
> > the
> > wrong resolution or bitrate.
> >
> > > So,
> > >
> > > a. Am I missing something that this makes this far more computationally
> > > intensive than I think?
> >
> > Nope. It's more a matter of automation. We need a tool that can
> > accurately do
> > keyframe edits based on the cutlist, remultiplex the results for
> > dvdauthor,
> > then create and burn a DVD image.
> >
> > > b. Am I missing an existing tool that does what I want?
> >
> > We all are. ;) As is common for open source tools, the building blocks
> > all exist. We simply need to build something polished with them. MythTV
> > is a shining example of this process, and it's still relatively young
> > yet.
> >
> > > Thanks,
> > > Len
> >
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