On Sun, 4 Jan 2004 [EMAIL PROTECTED] wrote:
> How does its speed compare to yuvscaler when encoding to
> similar quality (it that is possible anyway)? I have been
I haven't measured it - scaling is the least cpu intense activity
that's going on so that has never been the bottleneck.
> yuvscaler -v 0 -O SVCD -n n
>
> as a filter. What would be the scaling method whose resulting
> quality best aproximates to the yuvscaler call above?
Hmmm, what does yuvscaler use by default? I thought it was a simple
box or resample filter and that you had to specify the better
'bicubic' one with the -M BICUBIC option.
> I do not know yet when a chroma space conversion is needed.
You most likely do not have to worry about it unless you're
using use DV data in its original 4:1:1 format.
> needed. Is there a specific situation where chroma space
> conversion is required?
If you use either ffmpeg or smil2yuv to get 4:1:1 data then eventually
that needs to be converted to 4:2:0 before going to mpeg2enc.
Filtering (such as yuvdenoise for example) is best performed on the
original data (before it has been converted, resampled, whatever) - thus
I obtain 4:1:1 data with 'smil2yuv -i 2 inputfile.dv', do whatever
filtering (yuvmedianfilter, yuvdenoise, etc) is needed and then
'y4mscaler -O chromass=420_MPEG2' just before the 'mpeg2enc' command.
> Do the presets set a good scaling method? Or should I worry
> about learning them to choose one?
No, the scaling method still needs to be selected. A _very_ good one
is "-S option=sinc:4", but another good one (perhaps better for SVCD
use) is "-S option=cubicCR"
> $ mplayer -noframedrop -vo yuv4mpeg -nosound -v -osdlevel 0 \
> the.two.towers.avi -sub the.two.towers.srt -subpos 78 \
> -vf expand=:504
> $ cat stream.yuv |
> y4mscaler -O preset=SVCD |
> mpeg2enc -v 0 -I 0 -s -f 5 -V 230 -S 800 -a 2 -F 1 -n n -4 2 -2 1 \
> -b 2800 -B 284 -q 6 -K FILE=matrix.txt -R 0 -E -11 \
> -o the.two.towers.m2v
>
> But y4mscaler gives the messages:
>
> INFO: [y4mscaler] Input Stream Header:
> INFO: [y4mscaler] <<< frame size: 672x504 pixels (508032 bytes)
> INFO: [y4mscaler] <<< frame rate: 239759/10000 fps (~23.975900)
> INFO: [y4mscaler] <<< interlace: none/progressive
> INFO: [y4mscaler] <<< sample aspect ratio: ?:?
> **ERROR: [y4mscaler] Unknown norm; cannot determine SVCD format.
That's probably because the input frame size doesn't match one of
the NTSC sizes (Nx480). x504 is a very strange size, isn't it?
NTSC would be 640x480 or so wouldn't it?
Ah, I see the "-vf expand :504" in the mplayer command. Why is that
present? Perhaps if that was left out things would work better.
Is the data coming from a DVD? If so then do not have mplayer
expand/zoom the data - leave it as 720x480 and then y4mscaler will
see that it is a NTSC stream.
mplayer's yuv4mpeg output does not seem to get the header fields
right. That's why the sample aspect shows up as unknown "?:?".
Is the data really progressive? If so then the 'interlace: none'
is correct.
> Adding the option "-I norm=NTSC" to the y4mscaler command line does
> not help (the error message is the same from y4mscaler).
That is a bit of a mystery
Steven Schultz
-------------------------------------------------------
This SF.net email is sponsored by: IBM Linux Tutorials.
Become an expert in LINUX or just sharpen your skills. Sign up for IBM's
Free Linux Tutorials. Learn everything from the bash shell to sys admin.
Click now! http://ads.osdn.com/?ad_id=1278&alloc_id=3371&op=click
_______________________________________________
Mjpeg-users mailing list
[EMAIL PROTECTED]
https://lists.sourceforge.net/lists/listinfo/mjpeg-users
