Simple multiplexing and de-multiplexing - what does it really do?

[Swin]

Hi,

This may seem like an odd question but I ask for a reason. I have several SVCD's that I have wanted to re-backup and have had all sorts of problems with the mpg files that are on them. Eventually I install the mpeg 2 handler for TMPG and simply demuxed then remuxed the files. The resulting mpeg is of over 10 MB smaller than the original (not that thats a problem) but I just don't understand why splitting the streams then re-combining them should make such a difference?

The main reason for doing this was audio synch problems with my DVD player (Toshiba - known to have a problem) so re-imaging the MPEG using a patched VCDImage (via VCDEasy) solves the problem, but VCDEasy will not accept the original mpg at all, but after demux/mux all is cushty?

This is more of a informational question then anything else, I just hate not understanding.

Swin

[echooff]

when the files are mux-ed the headers are rewritten

[Mug Funky]

hey! what toshiba do you have?? i've got an SD-1300Y, and it plays SVCDs out of synch too. i emailed toshiba and they simply said that that model didn't play svcds... but it's got a Zoran Vaddis IV decoder chip which will do all this stuff. seems stupid, but i digress.

the reason the file is smaller is probably because of padding streams in the original files that were not re-muxed.

if you looked at the regular (not simple) demuxer, and loaded your source file, you'll probably see a padding stream.

[Swin]

Thanks, and indeed i do see that padding stream. I thought that headers wouldn't make that much difference in file size but i wonder if just re-writing those enables VCDEasy to "recognise" the MPEG again or weather these padding stream causes the problems. Still as said demux/remux does the job and now my curiosity has been satisfied as well. Well nearly - what is the padding stream for then? It just looks as though it takes up unnecessary space and causes problems?

Many Thanks.

Oh and as regard to the Toshiba problem, my model is actually a SD-220E, but follow this link to the guy’s site that has patched VCDImager - http://www.billh.demon.co.uk.

It may not work for you but as far as I can see, it hasn't caused any problems on other DVD players. The patch simply re-writes the first MPEG packet header in the stream.

Swin