On Thu, 19 Feb 2009, Thomas Kaiser wrote:
kilgota@xxxxxxxxxxxxxxxxxxxxxx wrote:
ID 0x093a:0x010e are working, because the image does not come out. Well,
Just if you don't know.....
ID 0x093a is the vendor ID from Pixart. Did MARS change the name to Pixart?
No idea. But the single camera which the module presently supports is the
Aiptek Pencam VGA+ which IIRC has a vendor number from Aiptek, not Mars.
So that much is consistent. Anyway, there are lots of dual-mode mr97310
cameras. Cf. libgphoto2/camlibs/mars.
What I found:
After shooting a raw frame, I get
FF FF 00 FF 96 64 D0 01 27 00 06 2D
There is the same Frame Header for the PAC207 and PAC7311 (FF FF 00 FF 96
..... 12 Bytes in total as I remember).
Yes, what you quote is the SOF marker for all of these cameras. The total
header length, including the SOF marker ought to be 12 bytes. On all of
the mr97310 cameras that I have dealt with, the last 5 bytes are obviously
related somehow to the image (contrast, color balance, gamma, whatever). I
have no idea how to interpret those values, but we can hope that someone
will figure out how. Thus, it is not a good idea to throw them away as the
driver is currently doing. If they have to be tossed, then toss them over
in libv4lconvert, I would say, instead of shaving them off in the driver.
It makes for much simpler driver code when one does not try to work around
them, too.
PAC207 does a line based compression and PAC7311 is jpeg based with a marker
in front of each MCU. Both decompression are supported by libv4l :-)
The marker for compression/no compression and for what kind of
compression if there is any is the next one that you do not quote here.
What i know from previous experience is
FF FF 00 FF 96 64 00 uncompressed
FF FF 00 FF 96 64 50 "standard compression" supported here and
in libgphoto2/camlibs/mars. Supports all cameras in stillcam mode except
for the next one listed
FF FF 00 FF 96 64 20 another compression, used by one stillcam, not
resolved
FF FF 00 FF 96 64 D0 new compression algorithm used by all the
0x093a:0x010e cameras that I own (several of them), when running in
streaming mode.
What else I know about this, or think I know:
Both the 0x20 format and the 0xD0 format are probably variants of the
differential Huffman encoding scheme which is the 0x50. One can see
sometimes a little bit of the picture, which is recognizable. But the
pattern is screwed up. For example, today I have been experimenting a bit
with the new one. I am pretty sure it starts from a different row, like
row 2 or so, instead of from row 0 as does the 0x50 algorithm. I have been
surprised before, but I will be very surprised indeed if the algorithm
signified by 0xD0 turns out to be one of the two you mention just now.
The PAC207 can be configured to run in raw mode or compressed mode. The same
should be possible to do with the PAC7311, but I could not find the right
register to set this :-(
Don't know if this info helps you? (or you already know)
No, I know nothing about how to do that. Heretofore, I have dealt with
these cameras as still cameras.
Incidentally, I did have something to do with solving the the 0x50
decompression. Bertrik Sikkens figured out the basics. It is a
differential Huffman encoding, as I said. One computes a "predictor" for
the next pixel to be decompressed by taking a weighted average of some
previously decompressed pixel data. Then one applies a "corrector" which
is the next piece of decoded data. Bertrik figured out the Huffman scheme,
as I said. What I did was to figure out the right pixels to average for
the predictor part and what weights they get assigned in the weighted
average.
But it seems that you know something about this kind of thing and probably
have the right tools or clues to be able to handle them. I have a couple
of other unsolved formats lying around, too. You might be the person I
have been trying to meet. Interested?
Theodore Kilgore
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