On Tue, 30 Mar 2004, Jonathan Woithe wrote:
> Using mjpegtools 1.6.2 and dvdauthor 0.6.9 I have observed another odd effect
> when playing the resulting DVD on a hardware player. The DVD was made from
> a number of mpegs each encoded with identical parameters with mjpegtools.
It's not odd at all - but rather the same problem that's come up
whenever folks try to simply 'cat' MPEG-PS (mplex'd/ProgramStream)
files together.
> They were made into a DVD following the dvdauthor examples given in the
> package (one after the other, no fancy titles/menus).
I do not know how well that works. It seems that the reports of
anomalies/artifacts/problems out number the success stories when it
comes to trying to append multiple program streams together.
> Every so often during playback, our Pioneer DV-344 hardware player will
> freeze at the transition between two source mpegs. It happens at about 10%
Yep - that's the same problem that seems to come up often.
One theory/idea is that it's a timestamp discontinuity at the splice
point - there's a gap introduced I think (at least there was at one
time) to make sure the timestamps don't overlap.
> on this player, every join is associated with a very brief, high bitrate
> peak. This seems strange to me because all the joins I have occur with the
> video faded to black (and sound faded out) - in other words, all the...
> the sharp transisition between two noise fields doing this, but since the
> black was produced by the computer in cinelerra this seems unlikely.
Actually that is precisely where I would expect a huge rate spike...
Pure black compresses down to almost nothing bitrate-wise, then comes
the motion and wham - the rate has to shoot way up before settling
down.
> I wonder whether there's something associated with the joins which causes
> some players to behave strangely - either due to mjpegtools or the way
> dvdauthor joins mpegs?
It's not mjpegtools - of that I'm quite certain. In fact if you
were to take the .m2v files, rip off the headers you _could_ cat
the multiple files together, then do the same thing with the audio
and mplex two large files together into one program stream.
That's approximately the way other dvd authoring tools handle
multiple files in a single track - you import/catenate multiple
.m2v and .ac3 (or .mp2) files together, the authoring progam handles
the removal of the headers and then does the multiplexing run itself.
No timestamp issues, etc to deal with at all in that scenario.
> Any thoughts anyone?
Other than arranging (via whatever editing tools are available/needed)
to have a single continuous .m2v file and a single audio file that
are mplex'd there's not a lot that can be done. I've shown how to
arrange for a continuous YUV4MPEG2 feed into the encoder from multiple
sources - it's just a little bit of shell scripting.
One thing that _might_ work is to put each .mpg file into a separate
track and arrange for the "at end" function of one track to jump
to the next one. That might introduce a brief delay as the
DVD player seeks but it won't lock/pause
The next best thing would be to have a 'm2vcat' program that could
deal with ES (elementary streams) and catenate them into a single
file (audio too but that could probably be done by taking the .wav
files, removing headers, etc).
Cheers,
Steven Schultz
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