From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266486AbUH1Ds7 (ORCPT ); Fri, 27 Aug 2004 23:48:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266487AbUH1Ds7 (ORCPT ); Fri, 27 Aug 2004 23:48:59 -0400 Received: from viper.oldcity.dca.net ([216.158.38.4]:24028 "HELO viper.oldcity.dca.net") by vger.kernel.org with SMTP id S266486AbUH1Ds5 (ORCPT ); Fri, 27 Aug 2004 23:48:57 -0400 Subject: Re: reverse engineering pwcx From: Lee Revell To: Craig Milo Rogers Cc: QuantumG , linux-kernel In-Reply-To: <20040828033552.GN24018@isi.edu> References: <412FD751.9070604@biodome.org> <20040828012055.GL24018@isi.edu> <20040828014931.GM24018@isi.edu> <412FF888.8090307@biodome.org> <20040828033552.GN24018@isi.edu> Content-Type: text/plain Message-Id: <1093664940.8611.8.camel@krustophenia.net> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Fri, 27 Aug 2004 23:49:00 -0400 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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