On Sun, 4 Jan 2004 [EMAIL PROTECTED] wrote:
> How do y4mscaler and yuvscaler compare when scaling a video stream for MPEG2
> encoding for SVCD, in terms of speed and image quality?
I've found y4mscaler to be better. Depending on the scaling method
chosen (and y4mscaler offers many to choose from) the speed can be
very fast to fairly slow. You have the choice of (and you can see
this with 'y4mscaler -S option=help') linear, quadratic, cubic,
cubicCR, cubicB, and sinc:N (where you can choose how many taps are
used - value of N is open to debate, the higher the value the slower
the speed but higher quality - reasonable value is 4, I tend to use 8).
The other thing I use y4mscaler for is the chroma space conversion -
usually to go from 4:1:1 to 4:2:0 but I have on occasion used it to
create 4:2:2 or 4:4:4 content for testing.
The presets are quite useful and do a good job of intuiting the
correct proceedure. For example if you send 720x480 frames into
"y4mscaler -O preset=CVD" it will do "the right thing" by cropping
8 pixels from each side and performing a 2->1 downscale to 352x480
(and not do the simplistic but wrong 720->352 scaling).
Try it, I think you'll like it ;)
Cheers,
Steven Schultz
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