Re: reverse engineering pwcx

Lee Revell
2004-08-28T03:48:59Z

On Fri, 2004-08-27 at 23:35, Craig Milo Rogers wrote:
> On 04.08.28, QuantumG wrote:
> > Craig Milo Rogers wrote:
> >
> > > Hmmm... a poster on Slashdot claims that entropy measurements
> > >imply that the pwcx code is interpolating rather that truly
> > >decompressing. Again, that's integer math and table lookups.
> > >
> > >
> >
> > http://www.amazon.com/exec/obidos/tg/detail/-/B00005R098/102-7619892-0201738?v=glance
> >
> > claims that the Logitech Quickcam Pro 3000 is a "True 640 x 480
> > resolution video capture" which is now clearly false.
>
> If the "now clearly false" is meant to be a consequence of the
> entropy measurements poster I referred to, I wouldn't jump the gun.
> On reflection, it's entirely natural for a decompressed stream to
> examine less entropy than the corresponding compressed stream!
>

Please see this slashdot thread:

http://linux.slashdot.org/comments.pl?sid=119578&threshold=3&mode=flat&commentsort=0&op=Change

The LavaRnd guys examined the pixels on the actual CCD chip. It's
160x120. The 'decompression' is just interpolation.

Lee