On Fri, 28 Nov 2003, Andras Kadinger wrote:
> And what about joining the encoded elementary streams _before_ multiplexing?
>
> Obviously my assumption is that mpeg2enc emits elementary streams, which
> contain no timestamps (please correct me if I'm wrong - I'm just
That should work ok.
However don't forget the audio.
> That would allow for independent per-chapter quality settings as
> requested, yet allow for multiplexing a single, seamless program stream.
Ah, ok - now I understand why someone might want to do that. The most
I have done along that line is to apply different filtering settings
to various portions of the stream but the settings to mpeg2enc
were "global" (same for the entire stream of all chapters) and only a
single large .m2v file was the output. That type of control can be
achieved with a small amount of shell script programming and using
'smil2yuv -c N".
What about the audio? You can't encode each chapter's audio
into a separate .mp2 (or .ac3) file and then catenate those together
without causing A/V sync problems (and possibly audible clicks/glitches
at the transition point).
Why? Because the last frame of the audio file will be padded to a
audio frame boundary. Effectively the audio is very slightly lengthened
at the end of the file. After a few chapter breaks the A/V sync
slip might become too high (the threshold depends on the viewer of
course).
Keeping the audio and video in sync during editing is a complex
task - catenating files together is just the beginning ;)
Of course if you're not using the audio from the camcoder because
you're adding a different soundtrack or just adding background music
without need for "lip sync" then the issues above do not become a
problem.
Cheers,
Steven Schultz
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