From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.kapsi.fi ([217.30.184.167]:45470 "EHLO mail.kapsi.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934146Ab1J3Pm3 (ORCPT ); Sun, 30 Oct 2011 11:42:29 -0400 Message-ID: <4EAD7061.3020007@iki.fi> Date: Sun, 30 Oct 2011 17:42:25 +0200 From: Antti Palosaari MIME-Version: 1.0 To: James CC: linux-media Mailing List Subject: Re: femon patch for dB References: <4EAB342F.2020008@lockie.ca> In-Reply-To: <4EAB342F.2020008@lockie.ca> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On 10/29/2011 02:01 AM, James wrote: > I added a switch to femon so it displays signal and snr in dB. > > The cx23885 driver for my Hauppauge WinTV-HVR1250 reports signal and snr > in dB. > > http://lockie.ca/test/femon.patch.bz2 from patch: human readable output: (signal: 0-65335, snr: 1/256 increments)\n" human readable output: (signal and snr in .1 dB increments)\n" You should take look to demod drivers and check what those are returning. I have strong feeling that most drivers returns SNR as 10xdB. And SS as 0-0xffff. I think there is good consensus of SNR unit, but for SS it is not so clear. For my drivers I have used SNR 10xdB and SS 0-0xffff. That's why, giving only those two alternatives is not suitable. Maybe it is better to set own param for SNR and SS? Devin did some research about SNR long time back: http://www.devinheitmueller.com/snr.txt regards Antti -- http://palosaari.fi/