[Ffmpeg-devel] upsampling of subsampled video data

[Attila Kinali]

On Mon, 11 Sep 2006 01:54:51 -0400
Dan Maas <dmaas at maasdigital.com> wrote:

> I would expect a converter to handle Rec. 601 (NTSC/PAL) coefficients
> as well as Rec. 709 (HDTV) coefficients. In both cases it would be
> nice to have two conversions, one that preserves the 16-235 range of
> Y'CbCr luma in RGB, and another that expands to 0-255 RGB.
> 
> Charles Poynton's book and website are good resources for this.

Which book do you mean? he wrote more than one :)

And yes, i still have to read a lot about that stuff.
I'd appreciate any good pointers.

> > The quantization levels for YUV are different from RGB and
> > requantizing the Y as RGB will introduce ugly banding.
> 
> One way to reduce banding is to use error-diffusion dithering. I get
> pretty good results on 8-bit to 8-bit conversions, at the cost of
> introducing some noise in the least significant bits. (I'd rather see
> a little noise than a lot of banding :)

Unfortunately, noise is something very difficult to generate
if you have only digital hardware. And i somewhat doubt
that it will make the image visualy any better (unless
the colour/luma gradients are calculated and dithering
is adjusted accordingly, but this is very difficult
in hardware)

				Attila Kinali

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