From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from smtp.nexicom.net ([216.168.96.13]:48820 "EHLO smtp.nexicom.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751394Ab1JZTpp (ORCPT ); Wed, 26 Oct 2011 15:45:45 -0400 Received: from mail.lockie.ca (dyn-dsl-mb-216-168-118-207.nexicom.net [216.168.118.207]) by smtp.nexicom.net (8.13.6/8.13.4) with ESMTP id p9QJjh79021535 for ; Wed, 26 Oct 2011 15:45:44 -0400 Received: from [127.0.0.1] (localhost [127.0.0.1]) by mail.lockie.ca (Postfix) with ESMTP id CB4F61E01A6 for ; Wed, 26 Oct 2011 15:45:42 -0400 (EDT) Message-ID: <4EA86366.1020906@lockie.ca> Date: Wed, 26 Oct 2011 15:45:42 -0400 From: James MIME-Version: 1.0 CC: linux-media Mailing List Subject: Re: femon signal strength References: <4EA78E3C.2020308@lockie.ca> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: unlisted-recipients:; (no To-header on input)@canuck.infradead.org Sender: linux-media-owner@vger.kernel.org List-ID: On 10/26/11 04:15, Devin Heitmueller wrote: > On Wed, Oct 26, 2011 at 12:36 AM, James wrote: >> My signal strength is always above 0 but when I use -H, it is 0%. >> Does that mean my signal strength is<0%? >> Maybe femon should report 0.x%. >> >> $ femon >> FE: Samsung S5H1409 QAM/8VSB Frontend (ATSC) >> status SCVYL | signal 00b9 | snr 00b9 | ber 00000000 | unc 00000000 | >> FE_HAS_LOCK >> >> $ femon -H >> FE: Samsung S5H1409 QAM/8VSB Frontend (ATSC) >> status SCVYL | signal 0% | snr 0% | ber 0 | unc 0 | FE_HAS_LOCK >> >> Is it normal to have<0% signal strength and still get reception? > For this demodulator, this is normal. The issue is there is no set > standard for the way in which signal level and SNR are reported in the > linux DVB API, and as a result there are numerous different formats. How many different formats are there (do I have to go through the archive)? Would it be feasable to change femon to handle different formats? femon was written by Johannes Stezenbach (see DVB-apps/szap/femon.c ). I'm going to try to change the code to at least work with my FE. :-) > The format the s5h1409 demodulator driver delivers it doesn't match > the demodulator that the person who wrote femon had available to > him/her (the s5h1409 delivers both fields in 0.1dB increments, while > whatever demod the femon author had to test with expected signal to be > 0-65535 and SNR to be in 1/256 increments). > > In other words if you have an SNR of 30.0 dB, femon sees 0x012c, which > it treats as a percentage of 0xffff which is 0.00457%, which gets > rendered as 0%. > > Unfortunately, the driver community has never been able to form a > consensus on how the data should be reported, so you cannot really > argue the s5h1409 driver is "doing it wrong" (numerous other drivers > report in the same manner as the s5h1409). You can read the mailing > list archive for the gory history. It really is a fine example of the > failure associated with "design by committee". > > Devin >