[Ffmpeg-devel] upsampling of subsampled video data

[Attila Kinali]

On Sun, 10 Sep 2006 23:39:04 -0400
Rich Felker <dalias at aerifal.cx> wrote:

> Also, it's ideal for the YUV->RGB to be done at the DAC level, not
> into a quantized RGB framebuffer. 

Sorry, DACs eat RGB, you cannot feed them YUV. The only thing
you can do is convert it with as much precission as possible
and feed as many bits as possible to the DAC.

But the primary objective of the card will be LCD monitors
which have their DAC on board and can only take 8bit/pixel/colour.
(Not to mention that most LCDs have still 6bit/pixel/colour resolution).

> The reason is that the quantization
> levels for YUV are different from RGB and requantizing the Y as RGB
> will introduce ugly banding. 

What does banding mean? I quick google didnt show up anything
relevant.

> I dunno if existing cards work around
> this or not, but it's yet another reason why YUV should be done as
> overlay and not blitter.

Somewhen YUV has to be converted to RGB. It does not
matter when and how you do it. If you do it wrong, it will
look wrong, no matter whether it was blitting or overlay.

			Attila Kinali

-- 
egp ist vergleichbar mit einem ikea bausatz fuer flugzeugtraeger
			-- reeler in +kaosu