Question about compression algorithm

[Jacob Nikom]

Thank you for pointing me to the right source. I have read the material 
but still have some questions.

Measuring the number of bytes which camera sends, I found that it
differs
between frames obviously due to compression. According to the
compression
algorithm if the pixel did not change between frames (with some
threshold)
its difference value is 0. 

Nevertheless, the camera still has to send this pixel to the host,
otherwise 
you loose the location of this zero pixel. Does it mean that the
compression 
algorithm works only by compressing the dynamic range of the pixels, not
their 
spatial information?

Also, is this way of compression common for all CCD and/or CMOS sensors?
Is there 
any "standard" set of commands for CMOS sensors or every company like
Photobit
or VLSI Vision produces its own "silicon vision machine"?

Thank you,

Jacob Nikom


Peter Pregler wrote:
> 
> On 30-Sep-99 Jacob Nikom wrote:
> > Hi,
> >
> > I wonder what compression coding is used for WebCamII?
> > Is it JPEG, MJPEG (JPEG for each independent frame) or
> > MPEG?
> 
> Sine none answered. The camera uses a 'send the pixels that changed
> somehow since the last picture' algorithm. The tricky part is of cause the
> definition of 'changed somehow'. Have a look at the Developers Guide for
> the CPIA-chip. There are commands SetCompression/SetCompressionParameters,
> etc. to control that stuff.
> 
> Greetings, Peter
> 
> -------------------------------
> Email: Peter.Pregler@risc.uni-linz.ac.at
> WWW:   http://www.risc.uni-linz.ac.at/people/ppregler
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