[theora-dev] YUV question

[Conrad Parker]

On Fri, Jun 04, 2004 at 12:29:33PM +0300, Makc wrote:
>
> The statement I care to make here, is simply that there ain't neither
> such thing as "luminance", which details "the eye is more sensitive to",
> nor "chromaticity", which details the eye is less sensitive to. What we

luminance and chromaticity are based on lots of research into
human vision. Yes, the maths is simple.

lossy codecs work by discarding information that humans cannot see. With
YUV, we're less sensitive to changes in U and V so we can simply store
the U and V components at a lower resolution, hence the 4:2:2 and 4:2:0
pixel formats.

> said: "YUV color is used in... TV broadcasts... Only the Y component of a
> color TV signal is shown on black-and-white TVs". Besides TV standards,
> nothing holds you fron using something like Y = R/4 + G/2 + B/4, which
> would considerably speed up codec, or sticking with good old 12-bit RGB.

although that would be faster to decode it would result in lower quality
images, because discarded information would be more noticeable.

Conrad.