[mythtv-users] Cutting commercials without expensive transcoding

[Preston Crow]

On Fri, 2004-03-12 at 00:58, Scott Nicholson wrote:
> I'm not a video expert by any means, but I'm pretty sure that this doesn't
> work due to the nature of MPEG video. MPEG isn't encoded as a bunch of
> single frames, but rather as "groups of pictures" (GOP), and if you try to
> cut a video file in the middle of a GOP you'll most likely lose sync with
> the audio.
> 
> If you only cut between GOPs the audio will sync better but you don't get
> frame-accurate cuts (i.e. the last 1/2 second of a commercial would still be
> there).
> 
> Now the video experts can jump in and correct me.

Yeah, you have to recompress a tiny fraction of your video, at least in
theory.  In practice, you have a scene change at the points where you
want to cut, so you should be able to get a perfect cut almost every
time.

As to Myth, I expect we all have a picture in our heads of a neat user
interface where we can define and adjust cut points (with the aid of
multiple commercial-detection algorithms), and then use those cut points
to watch the show, shrink the file, transcode if desired, and export the
file.

I would love to be able to clip a two-minute section of some show and
email it to a friend.

--PC