Re: New lossless image compression algorithm

On Feb 11, 11:22 am, spamt...@xxxxxxxxxxxx wrote:
I don't know if the Mars-Rover uses the YCbCr RCT of JPEG-2000,

No. All images are handled and compressed as individual black and
white images. The two color cameras have 12 filters, none of which
really correspond to the human eye's three filters, so neither YCbCr
nor RGB has meaning for that data. The filters are on a wheel that
rotates in front of each camera, and so n colors requires n images.
Which and how many filters are used depends on what's going on and how
much storage and downlink is available.

The compression software does not try to find correlations between
different colors, nor does it try to find correlations between stereo
pairs of images (eight of the nine cameras on each rover make up four
stereo pairs). Note that each Mars Exploration Rover uses a 20 MHz
RISC processor, which tends to limit what can be done, especially on a
limited energy and time budget.

During operations the camera commanding by the science teams does take
some advantage of the differences in the various channels. Typically
the left and right color cameras will both be commanded to take images
using the red filter (the dominant color on Mars) at, say 1 bit per
pixel compression. Then only one of the cameras will take images
using two or more other filters at 0.5 or 0.25 bits per pixel to get
some color for visualization. Sometimes many filters are used, all at
a high bit-per-pixel rate when we want to get some spectral data in
the visible / near-IR range.

Mark

.

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