[mythtv] mythtranscode MPEG2->MPEG2 issues

[Jay Love]

Based on that thread you referred to, it sounds like Geoff is struggling
with the ffmpeg muxer.  There doesn't seem to be much interest from the
ffmpeg team in muxing (very little cvs activity).  However, the
mjpeg-tools group actively works on their's and it seems to be the best
working muxer out there right now.

Is there any chance we can use the mjpeg-tools muxer instead of
libavformat?

Jay



On Tue, 2004-02-10 at 17:17, Paul Koster wrote:
> Based on some recent threads (e.g.
> http://www.gossamer-threads.com/perl/mailarc/gforum.cgi?post=102099;search_string=;guest=2272713&t=search_engine#102099 )
> I decided to dive a bit into mythtranscode to transcode from MPEG2->MPEG2 .
> 
> First of all I made a bunch of fixes related to the handling of (wrong)
> input parameters. I'll make up a patch in a few days for this.
> 
> Second, I did a number of tests transcoding a number of recordings without
> cutlists and one transcoding with cutlist. The results:
> - 4 files completed the transcoding without any problems (for details see
> below)
> - 1 file failed the transcoding because it encountered a block type of 0xba
> indicating a pack header
> - 2 files failed the transcoding because mythtranscode encountered a block
> type of 0xf4 (I've not been able to find out what kind of object this is)
> 
> For one of the files that completed the initial transcoding successfullly I
> repeated it with a cutlist (cutting of the end of a show) and tested the
> resulting file in a number of players:
> - it seems that the cutlist works okay, except that the last (few) frame(s)
> are still in there just at the end of the resulting file
> - the resulting file plays okay in the internal MythTV 'watch recording'
> option without noticable problems
> - the resulting file suffers from many artifacts at certain points
> (unrelated to the cutpoints ) when playing in Windows Media Player with the
> Elegard MPEG2 decoder (compared to the original)
> - the resulting file suffers from minor artifacts at certain points
> (unrelated to the cutpoints ) when playing in PowerDVD (compared to the
> original)
> 
> For the 3 files that failed:
> - the loop in mythtrans.cpp can't handle unknown object types and will get
> into an endless loop because it does not increase framelen, etc.
> - I tried to include support for type 0xba, but it seems that just skipping
> 12 (or 16?) bytes in the stream does not solve the problem as I've seen in
> comparable demuxers. I'll try to get a hand on some decent documentation to
> see if my PVR 250 outputs valid streams anyway.
> - should program streams work or is it just luck that they worked and is the
> current code still aimed at transport streams (as mentioned somewhere in a
> very old thread)?
> 
> All recordings were made with my PVR 250 ivtv 0.19 576x576 MPEG2 Program
> Stream 5000 kbps video, 384 kbps audio (mp2). To do the transcoding I used
> mythtranscode -i filename.nuv .
> 
> Are more people working on this issue beside Geoff (who has no time until
> march I read)? It would be so nice to have this feature working :)
> 
> --
> Paul
> 
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-- 
Jay Love <jsliv at jslove.org>