{mos_sb_discuss:18}
In the course of hacking the camera, a number of bonus features were
discovered that Ritz / Wolf Camera probably never intended. These are
mostly features of the underlying chipset (used in a variety of similar
cameras) which were never explicitly crippled for the Dakota single-use
camera.
Webcam mode
The Dakota camera supports streaming continuous
video in a variety of formats, ranging from raw 8-bit (B&W) to
compressed raw YUV (color) data. Varying sizes are available, including
352x288 and standard 640x480. This feature can be enabled by setting
the camera's mode to 3 (Webcam) via USB command, and the resulting data
can be read on the camera's Isochronous (ISO) USB pipe. This feature is
already implemented and working in Linux; see the SPCA50x USB Camera Linux Driver homepage for a Dakota-ready Webcam driver module.
Unfortunately,
most of the world runs Windows, and lack of a generic ISO driver or the
necessary time/skill to write one (especially one that will interface
with Windows' WDM video stream thingy or Video for Windows) has
prevented this feature from appearing in the Windows software.
Here is a sample image grabbed from gqcam in Linux; here is one frame
of the raw B&W data streamed to a file in Windows with a generic
'demo' USB driver, then converted from RAW with Paintshop Pro. There
are extraneous header bytes before each line of image data (I didn't
feel like writing any program to remove these), so the image is a bit
skewed (and there are little dots all over). And yes, I know I changed
the import image size to *641*x480; at the correct ratio the tearing is
even a bit worse due to those header bytes.
Technical notes:
Webcam mode image format is set by adjusting register 0x270c before
enabling Webcam mode. Available values are:
- 0: RawData10bit (line-by-line data with a short header at the beginning of each line and a longer one between frames)
- 1:
RawData8bit (black and white) (line-by-line data with a short header at
the beginning of each line and a longer one between frames)
- 2: YUV422Ncomp
- 3: YUV422Comp
- 4: YUV420Ncomp
- 5: YUV420Comp
Brightness, contrast and similar settings are set by registers as described in the reverse-engineered hardware documentation collected (in some instances discovered?) by John Maushammer.
AVI VideoClip mode
The
camera's chipset supports the ability to record short AVI movies in
addition to still images. At this time, however, this feature is only
available by forcing this mode while tethered to the USB port, where
picture-taking features are unavailable*. This could potentially be
made to work, but would require uploading modified firmware to the
camera. Also interesting to note; the chip would theoretically support
simultaneous audio (microphone) recording, but the audio-in pins are
unavailable on the particular small-form-factor chip package used in
the Dakota.
* There is an exception to this, as reported below.
'Take pictures while tethered to the computer' mode
When
this command is issued, the camera will take one or more pictures while
attached to the computer's USB port. Only USB power will be drawn; this
should work even if the camera has no batteries - however, the flash
will not be used, regardless of lighting conditions. The USB command
for this is 0x51 (Out), wIndex=0. wValue specifies the number of
pictures to take in succession (0 = 1 picture, 1 = 2 pictures, etc.).
Notes:
- Images
taken on USB power are of significantly reduced quality compared to
images taken the 'normal' way, probably due to the (lack of) power
available for the image sensor while running from USB power. They will
have that typical grainy 'Webcammy' look, and color/brightness may be
less than consistent. See the difference between images taken on battery and USB power.
- This
feature can be used to bypass the camera's hard-coded 25-picture limit,
and take pictures up until the camera's memory is actually used up. If
there are 25 pictures on the camera, it won't allow any more to be
taken by any means, either manually or via USB request. However, if
there are (for example) 24 pictures, and you use a single USB request
to take 2 more, the check at the 25th picture is bypassed. Now you can
continue taking shots (either via USB or the usual way) until the
memory is filled. Note, however, that the "Pictures Remaining" count on
the camera will not be valid while more than 25 pictures are stored.
- The
camera appears to have trouble storing more than 254 filenames in its
internal filesystem. If more than 254 pictures are taken, their
filenames will be duplicates of existing ones, resulting in hassles
while downloading and corrupted/lost pictures. (Luckily, in normal use,
it is highly unlikely that anywhere near this number of pictures can be
stored. This test was performed by covering the lens completely,
resulting in highly compressible all-black images. In this manner, 353
pictures were stored, but those after the 254th were corrupted.)
{mos_sb_discuss:18}
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