[Gphoto-user] New Mars cameras with new compression codec

[<ki...@ba...>]

Quite recently, I have encountered two MR97310 cameras which use a 
slightly different communication protocol and which use a new (for the 
Mars cameras) compression format. Unlike the older Mars cameras, there 
does not seem to be any choice to run without compression.

I have had some preliminary success in getting past the download of the 
configuration block, which works pretty much the same way on both the 
old-style cameras and on the newer ones, and I am able now to download 
some data after that.

Observed differences between the old cameras and the new ones include:

-- the older cameras downloaded the photos one at a time, and there was 
data in the configuration block, which indicated the size of the download 
for each. Thus it was possible to download the photos separately.

-- the newer cameras seem to dump out in a continuous stream whatever 
there is in the camera. The way that one photo is delineated from the next 
is not clear. One would think that there is some kind of marker or 
separator between the successive photos, but it is not clear what that 
marker must be. Also it is not so simple as to say that the memory of the 
camera simply gets dumped, because more bytes are downloaded if there are 
lots of photos than are downloaded if there are only one or two photos on 
the camera. Also the data in the config block which used to give the 
data sizes of the respective photos seems to have shifted in meaning 
and/or function.

-- the old cameras had a rather strange 3:1 fixed ratio compression mode, 
but one was not forced to use it. The newer cameras have a (or more than 
one?) compression mode(s) and it is not possible to avoid using it (them). 
And the compressed output does not seem always to be of the same size, 
though it is too early to be certain about that.

Another thing which is perhaps unfortunate from the user's or purchaser's 
point of view is that the newer cameras seem to be using a USB 
Vendor:Product ID already used by the older ones, namely 0x093a:0x010f


Anyone who wants to work on this new frustration of mine or thinks that 
he/she has something to offer is welcome. I would suspect that the worst 
problem would be to unscramble the data. I expect that sooner or later I 
will probably figure out where a photo begins and where one ends, though 
someone could well be quicker than I am about that, too.

Currently known "new" Mars MR97310 cameras include the Argus DC-1620 (and 
1610?) and an unknown camera from Sakar. I have been informed that the 
camera is the Sakar iConcepts camera, but after seeing one in the package 
and the specs written on it ("up to 152 photos") I have the suspicion that 
the iConcepts is probably an sq905; that is the exact capacity of many 
sq905 cameras running at 176x144 resolution, with 2:1 compression. 
Therefore I am not sure about the ID of the second Mars camera. In any 
case, whoever does not wish to spend his treasure in the service of the 
Linux revolution should not buy one of these, just now. But if you do buy 
one, then let's work on it.

Theodore Kilgore