[mythtv] MPEG2-MPEG2 transcoding: Illegal video stream
Thomas Börkel
thomas at boerkel.de
Thu Mar 2 08:48:32 UTC 2006
HI!
Geoffrey Hausheer wrote:
> On 3/1/06, Thomas Börkel wrote:
>> The resulting files all play OK in MythTV, but other programs report
>> illegal video streams for 2 out of 5.
> Can you play them with mplayer?
Yes.
> In general, you need to cut the 1st 10MB or so off the front of the
> stream, ensure that that smaller file is still broken, then send it to
> me.
Is download also OK?
http://www.boerkel.de/test.mpg
I can also provide the first 10 MB of the original file, if necessary.
Repro:
mpeg2desc -v0 < test.mpg > test.m2v
mpeg2desc -a0 < test.mpg > test.mp2
mplex -f 8 -o test2.mpg test.m2v test.mp2
mplex complains.
If you run "tcprobe -i test.m2v", it reports the wrong size and
framerate (NTSC instead of PAL).
Same problems with tcdemux/tcmplex.
>> When I try to demultiplex/multiplex them (I want to convert the audio
>> stream from mp2 to ac3), no multiplexer recognizes the video stream.
> This won't work with any tool I'm aware of (at least not reliably).
> The problem is that once you demux them, you lose the timestamp info,
> so there is no way to remux them and keep a/v sync when done. This is
> especially true if there are any issues with the input stream, or if
> you use the commercial-cut capability. There is some code in
> mpeg2parse to create streams that can be demuxed cleanly, but it is a
> nasty problem, and I never got it working reliably.
Yes, I know about the sync problem. Fortunately, this has not been a
problem for me in the past. ivtv recordings always have 79ms offset
(according to avidemux) and I provide that offset to mplex when muxing
them again after mp2->ac3. Even without that, I would not be able to
tell (79ms is small enough for my ears).
The cut recordings from MythTV 0.19 have even a smaller offset. With one
of those 3 that were OK, I demuxed, audio converted, requantized and
remuxed without sync problems.
Thomas
More information about the mythtv-dev
mailing list