On 5/19/05, Philip Nelson <[EMAIL PROTECTED]> wrote: > On Thu, 19 May 2005 19:09, Nick wrote: > > I'd also *never* recommend exporting a DVB file to mp4 (of which DivX, > > XVid etc all are) and then re-exporting to mp4 again. > > I was automatically transcoding all my recordings to mpeg4 to save disk space > while they were in mythtv, then later either deleted them or transcoding to > xvid to put on CD or something. I've done this for many other dvb recordings > and haven't had any problems before (and I was always very happy with the > quality of the xvid I ended up with).
I guess if the bitrate is high enough for the transcode, the reduction in quality may not be noticeable, especially on a TV screen. I have seen in the past that repeated re-encoding can introduce obvious artefacts in the picture, especially in higher motion scenes. > > You will lose a > > lot of quality in the process. The ideal process would be to take the > > DVB file, "fix" it if there are errors in the streams (there usually > > are in my UK recorded DVB files), make the cuts (using lossless GOP > > editing), and then export it to the final XVid file. This should > > ensure the highest quality output, and is likely to be much quicker > > also, as the intermediate mp4 is not used. > > This sounds good, as I've stopped the automatic myth transcoding now anyway. > So Program-X is what you use to "fix" the dvb file? Do you also use that for > the cuts? (I saw it has a cutlist feature) ProjectX! I actually use a program called Cuttermaran on my Win2K workstation for editing, and haven't looked into the ProjectX cutlist feature. I prob will now though, just to see how it goes. In either case, you want to be able to do GOP-accurate cutting, as this enables the MPEG2 stream to be broken up without needing to re-encode any of the video, and you may just lose a couple of frames if you can on non-I-frame boundaries. > I'm just wondering how myth is able to play the 'broken' transcoded mpeg4 file > so well - no a/v sync issues at all. If the file is still in the 'nuv' format (after the DVB is transcoded), that may go some way in explaining the sync still working. I think once the file is output into a non-nuv wrapped format, the sync issues may become obvious. I'm probably wrong though! Nick _______________________________________________ mythtv-users mailing list [email protected] http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
