4) avidemux2 will split the MPEG2-PS contents of the .nuv files into component .m2v video and .mp2 audio, using the cutlist to clip out commercials (using Xvfb to hide the gui from you)
This step here needs to be avoided... this is where the sync issues are caused.
nuvexport
1) Use nuvexport's mpeg2 -> mpeg2 cut option to export and commercial-cut your shows from Mythtv into standalone .mpg files. (which is using the same avidemux index, split/cut, lvemux re-combine process as above, all with Xvfb to hide the gui)
Again, if avidemux2 is used directly on the mpeg2 .nuv files, glitches in the stream that cause a change in A/V offset will break sync. Avidemux does not handle changing sync... only a static offset from beginning to end (which 95% of ivtv recordings have so it works most of the time)
If recorded at a DVD-friendly resolution with enough bitrate, the quality should be OK. I've found in general you need a fair bit more bitrate than a commercial DVD since the noise in the signal does not compress well.Video Quality
Once you get one of these processes working, you still may not be satisfied with the results. For example, I don't have my PVR-350 TV-out working yet, so I'm using an nVidia GeForce 2mx S-video output to my TV for now. I'm reasonably happy with the video quality given that my analog cable input is pretty bad to start with.
My viewpoint is that there are a few underlying issues that need to be solved:
1. Correct lossless MPEG2->MPEG2 cutting. This one has not been successfully done yet with any tools that I have found (mythtv or otherwise). Tools like GOPchop are close, but they're a little rough around the cutpoints. The potentially-changing A/V offset makes demuxing and remuxing impossible (at least without adding padding frames or something to fix sync variations). The elementary streams have *no* sync information as I understand it. This would provide space savings on archived mythtv recordings by removing the commercials without taking the time or the quality hit of transcoding.
1a. MPEG2->MPEG2 transcoding. Not completely without merit. The hardware scaling in the PVR-[23]50 cards makes for lousy recordings below 480x480, but burning up 704x480 resolution for a broadcast tv signal is wasteful of the space. My personal archival process involves recording at something fairly high (640x480) with a high bitrate, and then two-pass transcoding (with some denoising) to 352x480. That final image is *much* better than recording at 352x480 directly on the PVR-250, and is quite adequate for archiving broadcast-quality to DVD. I get about 4 hours of video on a DVD at VHS-SP quality. If I were to cut it down to <4 hours, it'd be even better than VHS-SP.
2. DVD authoring. *ONLY* after #1 (or #1a) are solved should anyone even think of messing with a fancy DVD authoring GUI. It's rather complicated to do well, and especially complicated to have menus with buttons, graphics, etc. That's a completely separate animal from having correct, cut MPEG2 files to begin with.
-Cory
************************************************************************* * Cory Papenfuss * * Electrical Engineering candidate Ph.D. graduate student * * Virginia Polytechnic Institute and State University * *************************************************************************
_______________________________________________ mythtv-users mailing list [email protected] http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
