Re: [Mjpeg-users] Creating a loop?

2004-01-27 Thread Andrew Stevens
Hi Steven,

  cat video.m2v  video2.m2v ; cat video.m2v  video2.m2v
  mv video2.m2v video.m2v
  mplex -f 8 audio.m2a video.m2v -o output.mpg

   I think if I see cat used with MPEG-2 files one more time I'll
   scream.

Actually, contactenating a MPEG-2 video elementary stream (an .m2v)  is 
*almost* concatenatable.  You need to strip the sequence end markers but 
thats about it (provided the sequences match in encoding parameters!!).

Obviously, for a multiplexed program stream: cat - forget it ;-)

cheers,

Andrew



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Re: [Mjpeg-users] Creating a loop?

2004-01-26 Thread Steven M. Schultz

On Mon, 26 Jan 2004, Lehmeier Michael wrote:

 I have created a menu-video for a dvd.
 It is only four seconds long, so when I use dvd options to loop it, the
 menu resets every four seconds, not enough to navigate.
 
 So I want to loop it before authoring it. Ten times should be enough.
 What I do now is something like that:
 
 cat video.m2v  video2.m2v ; cat video.m2v  video2.m2v
 mv video2.m2v video.m2v
 mplex -f 8 audio.m2a video.m2v -o output.mpg

I think if I see cat used with MPEG-2 files one more time I'll
scream.

EEK! 

:)

 The problem is that mplex now wants to split the output file at the end
 of every part I joined.
 
 Can I prevent this somehow?

Yes.

 Is there an other, easier way to create a loop?

Yes - and it was shown recently, but in case it has not made it into
the archives here's the basics:

Create a SINGLE continuous input of YUV4MPEG2 data into the encoder
and create a single .m2v file of the desired length.

The same principle applies to the audio as well because splicing 
.mp2 files together can result in A/V sync problems and/or clickspops
at the splice points.

Basically it goes like this:

#!/bin/sh

skip1()
{
read junk
cat
return 0
}

( \
 YUV4MPEG-producer#1; \
 YUV4MPEG-producer#2 | skip1; \
 YUV4MPEG-producer#3 | skip1; \
 YUV4MPEG-producer#4 | skip1; \
 ...
 YUV4MPEG-producer#10 | skip1;
) | mpeg2enc -f 8 -o video2.m2v

The only problem that needs to be dealt with is the extra YUV4MPEG2
headers that are produced by the additional Y4M producers - just read
the first line and throw it away.   At the end of the encoding there
will be a single continuous .m2v file.

Cheers,
Steven Schultz



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