On Fri, 19 Sep 2003, Richard Ellis wrote:
> Increasing -X a little (200 vs. 100) does seem to make -Q have a bit
> more effect, if the fact that the quant=xx.xx value bounces around
> much more during encoding is partially caused by -Q.
The test I ran (with an SVCD encoding) showed a ~1% increase in
the size of the file when I raised -X from 100 to 500 and used
-Q 2.0
Perhaps DVD resolution (and a higher bitrate) behaves differently.
Overall -Q, as you pointed out, doesn't seem to make much
difference these days.
> The -N parameter does work quite well for shrinking a file, but it
> seems it's a bit sensitive. In a test run, with -N 0.0 I got a file
> size of 748,032 kbyte. With -N of 0.1 I got 708,956 kbyte on the
> same input. The 40meg loss did drop it right into my target size
> window, so it worked for that, but I was expecting less drop from
39076/748032
.0522
39,076KB sounds like a lot but it's only 5%
What would be Really Interesting is a simple chart showing the
average bitrate (or filesize) for -N 0.2, 0.3 ... up to 1.0
For VHS type material -N 1.0 or perhaps even 1.5 works out fairly
good (and of course yuvdenoise is pretty much required ;)).
> I did try the kvcd matrices on a couple tests, and they did seem to
> produce very good images with a low bit rate as well. But upon close
> inspection of the TV output, it also seemed like I could see some
> edge ringing on sharp contrast changes.
Interesting. Perhaps the kvcd tables are more suited for some
times of material - the DVDs I created of cartoons (DV captures
from laser discs) came out looking astonishingly good. But they
were quite high on the bitrate - I set -q 4, -b 8500 and -K kvcd
(with a yuvdenoise -l 1 in the early stage to help cut out some of
the old film noise).
The tmpegenc tables might be a good middle ground between the
standard/default ones and the kvcd tables (which are aimed at
longer play time according to their website).
Cheers,
Steven Schultz
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