Re: [VCDImager] 2 feature-requests/suggestions

[ian]

On Mon, May 21, 2001 at 05:21:42PM +0200, Siegfried Hildebrand wrote:
> Hello list!
> 
> I have some suggestions about sdditional features.
> [warning! this is going to be very theoretical... ;-) ]
> 
Ok - I realise you're not suggesting these as alterations, and I have
to admit right now that I've not (yet) built an SVCD with this softawre,
but I would like to point out a couple of things.

> Since (I think) everybody wants to save every bit on the CD, it would
> be a good thing to take these 18bytes per I-frame out of the stream.
> 
Ok, assuming 12 frames per GOP and 25 frames per second (PAL), you
would be saving 36 bytes per second.  Assuming a really good case of
a 38 minutes SVCD, thats 2280 seconds, making a total of 82080 bytes.
At a nominal 2200kpbs bit rate, that would equate to .37 seconds
of extra footage.

Lowering the bitrate down to the minimum you personally find acceptable
and they your preferred target player will cope with will yield far
better results.

> Much more bytes are wasted by sequence-header-aligning. Which 
> means that padding packets are added.
> [snip]
> So, sequence-header-aligning seems to be necessary _only_ at 
> menu-jumpIn-points. 
>
Fair enough - I have not tried changing the stream this much, but
doesn't the fact that you get problems make it not such a good
idea ?  I mean, right now, on your chosen targets, these hacks
work just fine, but if you are starting to make a non-standard
stream, perhaps SVCD isn't such a good starting point.  Think
of the target PC/DVD/Mac/Other and then go and choose a codec
and bitrate to get the desired result.

> I know that my suggestions possibly violate the IEC-62107, but
> since SVCDs aren't made for eternity, and my player (for now)
> plays my slighty-out-of-the-spec-SVCDs fine, why not save some
> extra bits ;-)
>
Ok, so if your ideas are simply extra command line options, then
that's fine, but I'm more interested in storing home movies in
a way that will be good for the forseable future.  Yes, SVCD's
are not made for eternity - as soon as I can afford it I'll be
burning DVDRW's and choosing the stream bit rate that best
matches the input footage.

Since you mention it, which players have you tried these changes
on ?  I only have access to a Philips DV-525 (my own player),
as none of the players my friends have will take a CDR or anything
other than a VCD stream.

-- 
ian.