From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mta1.srv.hcvlny.cv.net ([167.206.4.196]:56331 "EHLO mta1.srv.hcvlny.cv.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755443AbZFHQbc (ORCPT ); Mon, 8 Jun 2009 12:31:32 -0400 Received: from host143-65.hauppauge.com (ool-18bfe0d5.dyn.optonline.net [24.191.224.213]) by mta1.srv.hcvlny.cv.net (Sun Java System Messaging Server 6.2-8.04 (built Feb 28 2007)) with ESMTP id <0KKX00CWWHWKY790@mta1.srv.hcvlny.cv.net> for linux-media@vger.kernel.org; Mon, 08 Jun 2009 12:31:33 -0400 (EDT) Date: Mon, 08 Jun 2009 12:31:30 -0400 From: Steven Toth Subject: Re: cx18, s5h1409: chronic bit errors, only under Linux In-reply-to: <4A2D3A40.8090307@gatech.edu> To: David Ward Cc: Devin Heitmueller , linux-media@vger.kernel.org Message-id: <4A2D3CE2.7090307@kernellabs.com> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7BIT References: <4A2CE866.4010602@gatech.edu> <4A2D1CAA.2090500@kernellabs.com> <829197380906080717x37dd1fd8n8f37fb320ab20a37@mail.gmail.com> <4A2D3A40.8090307@gatech.edu> Sender: linux-media-owner@vger.kernel.org List-ID: David Ward wrote: > On 06/08/2009 10:17 AM, Devin Heitmueller wrote: >> On Mon, Jun 8, 2009 at 10:14 AM, Steven Toth >> wrote: >> >>>> Please let me know how I should proceed in solving this. I would be >>>> happy >>>> to provide samples of captured video, results from new tests, etc. >>>> >>> When you tune using azap, and you can see UNC and BER values, what is >>> the >>> SNR value and does it move over the course of 30 seconds? >>> >>> -- >>> Steven Toth - Kernel Labs >>> http://www.kernellabs.com >>> >> Also, I believe UNC and BER display garbage when signal lock is lost, >> so do you see the "status" field change when the BER/UNC fields show >> data? >> >> Devin >> >> > Steven, Devin, > > Thanks for your replies. The signal and SNR are usually in the range > 0x0128 - 0x0140. They may increment or decrement on a per-second basis > but otherwise remain steady. The status field does not change most of > the time when bit errors occur, but it does lose the lock from time to > time for a second. Here is a representative sample: > > david@delldimension:~$ azap -r RTN > using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0' > tuning to 555000000 Hz > video pid 0x0051, audio pid 0x0052 > status 00 | signal 0000 | snr 0000 | ber 00000000 | unc 00000000 | > status 00 | signal 0000 | snr 0000 | ber 00000000 | unc 00000000 | > status 1f | signal 012e | snr 012e | ber 00001b04 | unc 00001b04 | > FE_HAS_LOCK > status 1f | signal 012c | snr 012e | ber 00000000 | unc 00000000 | > FE_HAS_LOCK Your SNR is very low, 0x12c is 30db. I assume you're using digital cable this is borderline. I like my cable system at home to be atleast 32db (0x140) bare minimum, it's typically 0x160 (36db) for comfort. It's possible that the tuner and 1409 driver are a little more optimized under windows. How much attenuation can you add under windows with signal loss? It's probably reasonably close to the edge also. -- Steven Toth - Kernel Labs http://www.kernellabs.com