In message , Bill in Co
writes:
Paul wrote:
Bill in Co wrote:
Well, this is a bit off topic, but I thought I'd just ask.

If one chooses to "grayscale" a video (remove the color info), can one
then
recompress the video a lot more while keeping the same video resolution
detail (i.e., due to eliminating wasting storage of any color information
in
the compressed file)?

I guess one could ask the same question regarding storing images, too.
IOW, could one convert a 1 MB color JPEG to perhaps 250 KB, and yet
retain
the same detailing (minus the color)


I tried it.
[]
Moviergb.wmv 56,671,234 bytes
Moviegray.wmv 50,380,744 bytes
[]
I suspect it may also be affected by the source of the colour
information in the video. If it's from older source material, where the
colour _difference_ signal has been bandwidth-limited (PAL, SECAM, NTSC,
video tape recorders), then it may be different from a video that
records the full RGB difference, as most modern material probably does.
I _suspect_ the ones with the bandwidth-limited colour difference signal
would give less reduction in size when greyscaled.

I think still images even uncompressed - i. e. BMP or similar - use
fewer bytes per pixel in greyscale. Colour ones often contain at least a
byte for each of the RGB elements of a pixel, making 24 bits; greyscale
images rarely benefit from more than 64K levels of grey (2 bytes), and
often 256 levels (1 byte) is sufficient.

It also depends a lot on the image type: if it has few
colours/greylevels (things like cartoons and logos), GIF can beat JPEG
(it certainly doesn't lose detail, i. e. is lossless).
--
J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

"The great tragedy of science, the slaying of a beautiful theory by an ugly
fact. - Thomas Henry Huxley