transcoding mpeg2 -> mpeg2 (was: RE: [mythtv] DVB, (new) recording profiles, and transcoding)

[Edward Wildgoose]

..snip...

Geoff.  How frequent are key frames in mpeg2? (I know I could look for myself, but I'm not near a suitable PC at the moment)

If they are pretty frequent then personally for the "non-re-encode" option I would be very happy if it just jumped to keyframes.  Probably you don't need to clip to keyframes though for the cut out, only the cut in again?

By keyframes I had assumed you meant GOP I-frames?  I was under the impression you didn't have these at regular intervals anyway, and could insert one for scene changes anyway?  

Hmm, sounds very complicated anyway.  I have a quick look at avidemux, but it says that it only does frameexact for mpeg4 (at least if there are backward referencing P-frames.)  

I did also find a reference to: http://gopchop.sourceforge.net/ which seems to do what we want (I haven't tested, just seen the website).

If I had a choice then I would envisage using transcode in one of two ways, a) either transcoding to mpeg4, possibly at a different resolution.  or b) not re-encoding, but just chopping commercials (I would have assumed that re-encoding to mpeg2 would only be for making svcd's and then a different and more manual interface would be appropriate)

Perhaps an appropriate interface would be to pop up a box with: "cut", or "re-encode" option when the user presses the "x" key?

Thanks Geoff

Ed W