On Sun, 5 Oct 2003, Maarten De Boer wrote:
> (played with a DVD player on a TV). Then I created the SVCD (standard
> settings). expecting it to be even better, but in fact it contained a
> lot of artifacts (the wringling on large surfaces around borders, I
> don't know the slang for)
The technical term is "not enough bits" :)
> Now, I realize the SVCD bitrate has been a bit lower than the VCD bitrate
> I used, but only slightly. Maybe the VCD is smoother because I used
> yuvdenoise in the chain? Or maybe because the VCD resolution is a lot
If yuvdenoise was used for VCD then it is even more important to
use yuvdenoise with SVCD because proportionally there are
fewer bits/pixel.
I'll use NTSC dimensions - doing the calculations for PAL is
left to the reader ;)
VCDs have a standard bitrate of ~1150kb/s. You used the SVCD
rate of 2500 which is ok if your player can handle it - but it is
non-standard.
VCD is 352x240 so there are 84480 pixels which gives 1152000/84480
bits/pixel or 13.6
SVCD is 480x480 or 230400 pixels/frame. To maintain the same
number of bits/pixel as VCD one would need (480*480)/(352*240) *
1150kb/s or 2.727 the bitrate or 2.727*1152kb/s = 3136kb/s
You can see that SVCD is on the edge of not having enough bits
at 2500.
> something wrong when creating the SVCD?
First thing is that you didn't use yuvdenoise ;)
> cat oulala001.dv | raw2yuv -i 0 | yuvdenoise -F | yuvscaler -O VCD |
> mpeg2enc -f 2 -b 2500 -s -H -B 224 -o video.mpg
Using ~2500kb/s for VCD will give great quality because there are
so many bits available.
>
> cat oulala001.dv | raw2yuv -i 0 | yuvscaler -M BICUBIC -O SVCD | mpeg2enc
> -q 9 -f 4 -B 224 -I 1 -4 2 -2 1 -o /mnt/winF/oulalaSVCD/svcd.mpg
There are several things that can be done to reduce the average
bitrate:
1) Add 'yuvdenoise -l 1' (a mild setting) to the pipeline
2) Add "-N 0.5" (or perhaps a little higher but values over 1.0
are not recommended) to the mpeg2enc parameters
3) Try the KVCD matrices - add a "-K kvcd" to the mpeg2enc
options.
1 and 3 can be used at the same time. It might not hurt anything
to use all three but I think using -N and "-K kvcd" at the same
time will degrade the picture. -N and "-K tmpgenc" would
probably work together ok though.
There has been a report (I forget who did the tests) of "-K kvcd"
producing very good looking SVCDs.
I'd definitely add a yuvdenoise step.
Good Luck!
Steven Schultz
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