On Thu, 5 Mar 2009, Thomas Kaiser wrote:
Hello Theodore
kilgota@xxxxxxxxxxxxxxxxxxxxxx wrote:
On Wed, 4 Mar 2009, Thomas Kaiser wrote:
As to the actual contents of the header, as you describe things,
0. Do you have any idea how to account for the discrepancy between
From usb snoop.
FF FF 00 FF 96 64 xx 00 xx xx xx xx xx xx 00 00
and
In Linux the header looks like this:
FF FF 00 FF 96 64 xx 00 xx xx xx xx xx xx F0 00
(I am referring to the 00 00 as opposed to F0 00)? Or could this have
happened somehow just because these were not two identical sessions?
Doesn't remember what the differences was. The first is from Windoz
(usbsnoop) and the second is from Linux.
1. xx: don't know but value is changing between 0x00 to 0x07
as I said, this signifies the image format, qua compression algorithm in
use, or if 00 then no compression.
On the PAC207, the compression can be controlled with a register called
"Compression Balance size". So, I guess, depending on the value set in the
register this value in the header will show what compression level is set.
2. xx: this is the actual pixel clock
So there is a control setting for this?
Yes, in the PAC207, register 2. (12 MHz divided by the value set).
3. xx: this is changing according light conditions from 0x03 (dark) to
0xfc (bright) (center)
4. xx: this is changing according light conditions from 0x03 (dark) to
0xfc (bright) (edge)
5. xx: set value "Digital Gain of Red"
6. xx: set value "Digital Gain of Green"
7. xx: set value "Digital Gain of Blue"
Does anyone have any idea of how actually to use this information/ for
example, since a lot of cameras are reporting some kind of similar looking
information, does anyone know if there are any kinds of standard scales for
these entries? Just what are they supposed to signify, and how exactly is
one supposed to use such values, if they have been presented? When I say "a
lot of cameras," understand, I mean still cameras as well as webcams, and
cameras with a lot of different chipsets in them, too. So this is a
question whether there is any standard system for the presentation of such
data, and how it might constructively be used in image processing. I have
had questions about this kind of thing for a long time, and I do not know
where to look for the answers.
For the brightness, I guess, 0 means dark and 0xff completely bright (sensor
is in saturation)?
That of course is a guess. OTOH it could be on a scale of 0 to 0x80, or it
could be that only the digits 0 through 9 are actually used, and the basis
is then 100, or too many other variations to count. Also what is
considered a "normal" or an "average" value? The trouble with your
suggestion of a scale from 0 to 0xff is that it makes sense, and in a
situation like this one obviously can not assume that.
What I am suspecting is that these things have some kind of standard
definitions, which are not necessarily done by logic but by convention,
and there is a document out there somewhere which lays it all down. The
document could have been produced by Microsoft, for example, which
doubtless has its own problems reducing chaos to order in the industry, or
by some kind of consortium of camera manufacturers, or something like
that. I really do strongly suspect that the interpretation of all of this
is written down somewhere. But I don't know where to look.
Theodore Kilgore
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