Re: Fixing mpeg2enc

>>If we could only get the mpeg2enc guy to come in from the cold, and
>>fix the nasty bugs that I can reproduce easily, we could finally
>>have a bona fide good reason to release a new version of mjpegtools!
>
>Well...  you might just be in luck!  I've currently got some vacation
>to use up and may well be going freelance in a few months time.

Sweet!  Finally, I'll be able to nail down the last few flaws in my open-source video-processing pipeline!  I'm excited!

>However is really any role for mpeg2enc these days?  I thought ffmpeg
>did a pretty decent job these days.

I've been trying to use ffmpeg to encode DVD-grade video from analog sources, and no matter how hard I try to push the bitrate or the quantization level, or the other parameters that are supposed to increase quality, my scenes look blocky.  I've asked the mailing list for ideas, but no one seems to know.  (I ended up tangentially helping someone ELSE with their mpeg2enc problems. :-)

ffmpeg does transcoding really well, but stinks at analog-video encoding.  When I need to produce a non-MPEG1/2 format (e.g. Flash format, for YouTube), I encode the video with mpeg2enc, and then have ffmpeg transcode it to the format I want.  That's the only way I've been able to get good results out of ffmpeg.

>If there's really still a niche for mpeg2enc and you can sync me up
>on the bugs with some nice sample files I'll get it working ...
>promise!

I'll start working on demonstration files right now.  But just to get your mind working in the right direction:

[1] MPEG-1 encoding is really broken.  It looks like something's overflowing in the DCT conversion (or whatever that step is called).  I can produce a short clip that generates major artifacts.

[2] MPEG-2 encoding still has that overflow issue with "-q 1".  It doesn't happen often, just often enough to make my DVDs look unprofessional.  The strange thing is, it looks perfect when I view it on my computer -- it just artifacts when played on an actual DVD player.  I can provide you with short clips that reproduce the problem.

[3] The most-recent bitrate estimation code seriously undershoots the target.  The previous code (which, it looks like, I grabbed from CVS around March 15, 2005) does a much better job.

[4] The most-recent mplex code seems to have serious trouble with A/V sync.  It looks perfect when viewed on my computer, but gets out of sync when played on an actual DVD player.  It was especially bad on a PAL-format DVD I did a few years ago (most of my analog-video sources are NTSC, but I had a friend with a PAL tape that he wanted converted.)  Again, the mplex from CVS around March 15, 2005 did a better job, though it was still a little out of sync.  (I've been using what I call "mpeg2enc-170" and "mplex-170" for a long time now.)

There may be other problems, but those are the ones I can think of off the top of my head.  I'll find any others as I continue to convert my analog-video collection to DVD, which I've been doing lately in a big way.

Rest assured that I will test the heck out of your code, so your efforts won't be wasted nor unappreciated!

Steven Boswell

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