Return-Path: Received: from mtain-dd02.r1000.mx.aol.com (mtain-dd02.r1000.mx.aol.com [172.29.64.142]) by air-md01.mail.aol.com (v129.4) with ESMTP id MAILINMD012-8b754da1e8e51a8; Sun, 10 Apr 2011 13:29:09 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dd02.r1000.mx.aol.com (Internet Inbound) with ESMTP id C28E0380000B0; Sun, 10 Apr 2011 13:29:06 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Q8yPk-0005zr-0t for rs_out_1@blacksheep.org; Sun, 10 Apr 2011 18:27:08 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Q8yPj-0005zi-Br for rsgb_lf_group@blacksheep.org; Sun, 10 Apr 2011 18:27:07 +0100 Received: from mout2.freenet.de ([195.4.92.92]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Q8yPi-0005sM-PZ for rsgb_lf_group@blacksheep.org; Sun, 10 Apr 2011 18:27:07 +0100 Received: from [195.4.92.21] (helo=11.mx.freenet.de) by mout2.freenet.de with esmtpa (ID dl4yhf@freenet.de) (port 25) (Exim 4.72 #5) id 1Q8yPi-0001GF-03 for rsgb_lf_group@blacksheep.org; Sun, 10 Apr 2011 19:27:06 +0200 Received: from blfd-4db0fad1.pool.mediaways.net ([77.176.250.209]:2334 helo=[192.168.0.101]) by 11.mx.freenet.de with esmtpsa (ID dl4yhf@freenet.de) (TLSv1:CAMELLIA256-SHA:256) (port 465) (Exim 4.72 #3) id 1Q8yPh-00056Z-Mo for rsgb_lf_group@blacksheep.org; Sun, 10 Apr 2011 19:27:05 +0200 Message-ID: <4DA1E868.107@freenet.de> Date: Sun, 10 Apr 2011 19:27:04 +0200 From: wolf_dl4yhf User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv:1.9.2.15) Gecko/20110303 Thunderbird/3.1.9 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <4DA02769.9090003@talktalk.net> <4DA0B615.8060502@iup.uni-heidelberg.de> <4DA0BF27.9020705@talktalk.net> <4DA0C3DB.5000509@iup.uni-heidelberg.de> <4DA169F0.70506@freenet.de> <4DA18B81.4060807@iup.uni-heidelberg.de> <4DA1970A.2050802@freenet.de> In-Reply-To: X-Spam-Score: 1.4 (+) X-Spam-Report: autolearn=disabled,RATWARE_GECKO_BUILD=1.426 Subject: LF: Re: GPS Sync Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=none autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false x-aol-global-disposition: G x-aol-sid: 3039ac1d408e4da1e8e17b82 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) Hello Andy, Thanks for the info . I will check it with some other (cheaper) soundcards, but the E-MU 0202 is the only one I have which really supports 192 kS/sec for the analog input. you wrote: > But I'm impressed you can get that good averaging from a sampling rate > much lower than that It was a suprise for me as well, thus the scepticism. The principle is as follows: - Interpolate the samples from the soundcard (192 kS/s) by a factor of four - Run a few dozen of those interpolated samples (around the rising edge) through a 2000-point FIR filter, windowed-sinc lowpass with ~96 kHz cutoff = nyquist frequency of the original signal. Going larger than 2000 points doesn't improve the result any further, going below 1000 points makes it worse. - Use the four samples from that signal around the zero-crossing (or steepest slope) for a cubic interpolation - Find the zero-crossing in that interpolated function, to calculate the fractional part for 'number of samples between two rising GPS sync pulses'. All further calculations (statistics, momentary sampling rate, averaged sampling rate) are based on that result. If anyone is interested, I will publish the sourcecode (plain old "C") after some clean-up. 73, Wolf .