On Tue, 25 Jan 2005, E.Chalaron wrote:
HI!
I see this item was delayed in the queue for quite some time. I
saw a reply long before the actual start of the thread arrived.
Strange.
> INFO: [mpeg2enc] Aspect ratio code: 1 = 1:1 pixels
Oops - but I think I know what caused that problem...
> here is the line I am using
>
> cat *.ppm | ppmtoy4m -F 18000:1000 -L | y4mscaler -I sar=1:1 -O size=720x576
> -O chromass=420_MPEG2 -O sar=PAL | yuvdenoise -b 20,20,680,536 -r 16 -t 2 -c
It's probably necessary to specify the output SAR (-O sar=) before
you give the size (-O size). That's so that y4mscaler knows
what output sample aspect to use when doing the scaling.
Try putting put the -O sar before the -O size thus:
y4mscaler -I sar=1:1 -O sar=PAL -O size=720x576 -O chromass=420_MPEG2
I would use 704x576 instead of 720x576
y4mscaler -I sar=1:1 -O sar=PAL -O size=704x576 -O chromass=420_MPEG2
Why? Because 704x576 using 59:54 pixels *exactly* represents a 4/3
image and 720x576 59:54 does NOT. So if you're coming from 1024x768
(which is a 4/3 image using 1:1 pixels) it makes sense to go (exactly)
to another 4/3 representation (704x576 59:54).
But if you really want the 720xN size that's fine (perhaps you're
editing the clip into a large show and all the clips need to have
the same encoded frame size):
y4mscaler -I sar=1:1 -O sar=PAL -O preset=DVD -O chromass=420_MPEG2
If you're not using the latest (8.1) y4mscaler then you really
really want to add a "-S option=sinc:5" or similar to the options
otherwise you'll end up using a simple 'linear' scaling kernel.
-->> The other thing that you probably should add is a "-O infer=exact".
For example when scaling one 16/9 picture (1920x1080 1:1) to another
(704x480 40:33) with the default "-O infer=simplify" I get:
INFO: [y4mscaler] < 1920x1088, SAR 1:1, top-field-first
INFO: [y4mscaler] < chroma subsampling: 4:2:0 MPEG-2 (horiz. cositing)
INFO: [y4mscaler] < chroma ss ratios: x 1:2 y 1:2
INFO: [y4mscaler] < active region:
INFO: [y4mscaler] < 1877.333333x1056.000000 at 21.333333,12.000000
INFO: [y4mscaler] < matte region:
INFO: [y4mscaler] < 1920x1088 at 0,0 (bg Y'CbCr: 16,128,128)
INFO: [y4mscaler] === SCALING parameters: ================
INFO: [y4mscaler] | Scaler: Matto's Generic Scaler
INFO: [y4mscaler] | kernels: sinc:6, sinc:6
INFO: [y4mscaler] === TARGET parameters: =================
INFO: [y4mscaler] > stream:
INFO: [y4mscaler] > 704x480, SAR 40:33, top-field-first
INFO: [y4mscaler] < chroma subsampling: 4:2:0 MPEG-2 (horiz. cositing)
INFO: [y4mscaler] < chroma ss ratios: x 1:2 y 1:2
INFO: [y4mscaler] > active region:
INFO: [y4mscaler] > 704x480 at 0,0 (bg Y'CbCr: 16,128,128)
INFO: [y4mscaler] > X ratio: 3/8
INFO: [y4mscaler] > Y ratio: 5/11
INFO: [y4mscaler] Output Stream Header:
INFO: [y4mscaler] >>> frame size: 704x480 pixels (506880 bytes)
Note how the active region was cropped to '1877x1056'. The aspect
will be correct but the results weren't the anticipated ones.
However adding "-O infer=exact":
INFO: [y4mscaler] < 1920x1088, SAR 1:1, top-field-first
INFO: [y4mscaler] < chroma subsampling: 4:2:0 MPEG-2 (horiz. cositing)
INFO: [y4mscaler] < chroma ss ratios: x 1:2 y 1:2
INFO: [y4mscaler] < active region:
INFO: [y4mscaler] < 1920.000000x1080.000000 at 0.000000,0.000000
INFO: [y4mscaler] < matte region:
INFO: [y4mscaler] < 1920x1088 at 0,0 (bg Y'CbCr: 16,128,128)
INFO: [y4mscaler] === SCALING parameters: ================
INFO: [y4mscaler] | Scaler: Matto's Generic Scaler
INFO: [y4mscaler] | kernels: sinc:6, sinc:6
INFO: [y4mscaler] === TARGET parameters: =================
INFO: [y4mscaler] > stream:
INFO: [y4mscaler] > 704x480, SAR 40:33, top-field-first
INFO: [y4mscaler] < chroma subsampling: 4:2:0 MPEG-2 (horiz. cositing)
INFO: [y4mscaler] < chroma ss ratios: x 1:2 y 1:2
INFO: [y4mscaler] > active region:
INFO: [y4mscaler] > 704x480 at 0,0 (bg Y'CbCr: 16,128,128)
INFO: [y4mscaler] > X ratio: 11/30
INFO: [y4mscaler] > Y ratio: 4/9
INFO: [y4mscaler] Output Stream Header:
INFO: [y4mscaler] >>> frame size: 704x480 pixels (506880 bytes)
Note the different X and Y ratios AND the fact there is no
cropping/padding . The 1920x1080 1:1 goes cleanly into 704x480 40:33
as expected.
> Or either using yuvfps ?
You might give yuvfps a try and see how it looks.
Cheers,
Steven Schultz
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