[MPlayer-users] About CVCD

[Steffen Barszus]

On Thursday 05 December 2002 11:56, Santiago Muelas wrote:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> Hello,
> Someone has given me recently, a CD with a movie and told me that it was
> NOT "VCD", nor "SVCD" but "CVCD". 

Didn't you meant CVD ? For that take a look at vcdhelp.com. should be possible 
on Linux too. Let me explain it a littlebit:
(All Pal)
VCD => 352x288 /mpeg1 => because of mpeg1 bad compression.
SVCD => 480x576 /mpeg2 => better compression trough mpeg2 but higher 
resolution. 
CVD => 352/576 /mpeg2 => good compression trough mpeg 2 and lower resolution 
vertically, which is almost not seeable on normal TVs, since the 
TVs-resolution depends on lines and the horizontal "resolution" mainly 
depends on the signal-quality. In most cases the signal quality isn't better 
then these 352. Trough the lower resolution there is lower information that 
must be compressed , so you have with lower bitrates lesser 
compression-artefacts.
352x576 is a standard pal-mpeg2 resolution, so most dvd's accept these cd's, 
sometimes even if the dont play svcd's. The next Pro for this format is that 
it is a standard resolution for video-dvd too, so you can take the same mpeg 
for both media. 
I did a try with that resolution under linux, but the result was really bad 
(Note: I tried with tosvcd so the image was scaled with yuvscaler, I guess 
thats the problem, even with bicubic it wasn't good. Didn't try the new 
y4mscaler. Maybe in mencvcd mplayer does the scaling). 
The next problem is the mpegencoder. mpeg2enc is as I know the only 
mpeg2encoder under linux and these encoder really have problems:

- at low bitrates (sometimes blocky)
- sharp edges ( ringing affect (a lot ! at least in my experimrents))
- size prediction ( you can only give the quantesizer , no average bitrate or 
something like that, maybe it can be steered by lowering the max-bitrate and 
hopefully does not produce crap at highbitrate-scenes)

The next problem I see is that the max-time of svcd is AFAIK 79:30 ( near 
80:00 min at least) so I dont see how there can be 90 min on that cd.

If someone tells me I am false at some or all facts , I'll be happy to learn 
the right ;)

Hope this helps a littlebit. 

BTW: the 352x576 resolution can easily be given to yuvscaler so no technical 
problem to do so ;)

Greets

Steffen


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