Re: [VCDImager] delay between tracks on an SVCD

[Jorgensen, Jens]

address@hidden wrote:

> Christoph Scheurer <address@hidden> writes:
>
> > I think I read somewhere that it is possible to create multi-track SVCD's
> > without these delays. Is that also possible with vcdimager? I couldn't find 
> > an
> > answer to this question in the mailing list archive.
>
> I've recently seen a thread about this in the http://www.vcdhelp.com
> forums.  I can't give precise information for finding the thread at
> the moment, I can't get to the site.

I'm familiar with the SVCD standard and I'm guessing that in order to get 
no-delay transitions between tracks you need to use the Play Sequence 
Descriptor file (PSD.SVD). This is an optional file and is also the means for 
creating menus. This file is just a bit complicated and I don't think it's 
supported yet.

> The synopsis was that there was the correct way of providing DVD like
> "chapters" and a way to do it by playing games with the .cue file and
> avoid the delays.  The second way was not standards compliant and
> would only work on some players.
>
> You made one mpg file with all the tracks concatenated together and
> make a note of the "start" times of each of the tracks and add
> additional lines to your .cue file with this information.  (Similarly
> to making a Disc at Once CD-DA disc.

The second 'non-standards-compliant' way probably takes advantage of the fact 
that if you burn a disc in DAO mode you can specify non-standard track gaps. 
You see tracks are supposed to have gaps of empty sectors in front of them. 
What's more, here's what the SVCD standard says about MPEG tracks:

 "An MPEG track starts with a Pause encoding of minimum 150 Empty sectors. Thus 
a movie, which needs to be played back seemlessly, shall be recorded in one 
track." (emphasis from original)

The other way to have MPEG video in your SVCD is add it as a Segment Play Item. 
Note though that a Segment Play Item is stored in the data track which means 
wasted bits since the data track is written as Mode 2, Form 1 sectors. A Mode 
2, Form 1 sector contans 2048 bytes which includes ECC bytes which a regular 
MPEG track is written as Mode 2, Form 2 sectors, each having 2324 bytes. That's 
18% more space!

Now, when you use the PSD you can specify wait times after an "item" has been 
played. It is possible to specify a zero wait time and doing this may get rid 
of the pause. I don't know because I haven't tried this but it seems like the 
docs suggest this is possible.

> There was a description of how to do it right.  This would have to be
> done by vcdimager I think and I don't know if the description was
> precise enough to implement.

As Herbert said before the definitions of the structures for the PSD.SVD and 
*all* other possible files are present in the source. I believe he extended a 
warm invitation to anyone wanting these features to go ahead and write up the 
code to support them. I'll also offer what assistance I can with respect to how 
the standard says things are supposed to be done.

--
Jens B. Jorgensen
address@hidden