Jean-Francois Moine wrote:
On Tue, 17 Feb 2009 20:35:28 +0100
Thomas Kaiser <v4l@xxxxxxxxxxxxxxx> wrote:
Jean-Francois Moine wrote:
BTW, I am coding the subdriver of a new webcam, and I could not find
how to decompress the images. It tried many decompression functions,
those from the v4l library and most from libgphoto2 without any
success. Does anyone know how to find the compression algorithm?
Hello Jean-Francois
Do you have some more information about the cam and the stream?
Do you know the frame header?
Any idea what the compression should be?
Can you provide a raw stream from the cam?
Hello Thomas,
The cam is a Tascorp 17a1:0118. I have USB traces. Starting the webcam
is easy, and so is extracting the images (0x02 + 0xa0/0xa1 at start of
image packets and 0x5a + 0xa5 for end of image with average luminosity).
I attach an image I extracted by hand from the trace, removing the 2
bytes of the packets. If it can help, I may send you the whole USB trace
(3 Mb) and/or other images.
Cheers.
Hello Jean-Francois
Thanks, for the frame (or frames?). What resolution did you use while
recording this stream?
Can you put your USB trace somewhere on the net where I can download it?
When I was guessing the streams of webcams, I used to get the sensor
into saturation -> complete white picture. So you know how the decoded
picture should look like ;-)
Actually, it is quite easy to get a webcam sensor into saturation. Just
remove the lens of the cam an put a light in front of it. Check in
Windoz if the picture is really complete white and then record a stream
in Linux. Now, you should get a very homogeneous stream. Look at it and ....
I hope you got the idea?
Thomas
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