From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from ffm.saftware.de ([83.141.3.46]) by www.linuxtv.org with esmtp (Exim 4.63) (envelope-from ) id 1KrWjg-00050f-Rt for linux-dvb@linuxtv.org; Sun, 19 Oct 2008 13:46:19 +0200 Message-ID: <48FB1E04.90408@linuxtv.org> Date: Sun, 19 Oct 2008 13:46:12 +0200 From: Andreas Oberritter MIME-Version: 1.0 To: Matthias Schwarzott References: <412bdbff0810171104ob627994me2876504b43c18d8@mail.gmail.com> <200810182138.02988.zzam@gentoo.org> In-Reply-To: <200810182138.02988.zzam@gentoo.org> Cc: linux-dvb@linuxtv.org Subject: Re: [linux-dvb] [RFC] SNR units in tuners List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: linux-dvb-bounces@linuxtv.org Errors-To: linux-dvb-bounces+mchehab=infradead.org@linuxtv.org List-ID: Matthias Schwarzott wrote: > On Freitag, 17. Oktober 2008, Devin Heitmueller wrote: >> Hello, >> >> In response to Steven Toth's suggestion regarding figuring out what >> the various units are across demodulators, I took a quick inventory >> and came up with the following list. Note that this is just a first >> pass by taking a quick look at the source for each demodulator (I >> haven't looked for the datasheets for any of them yet or done sample >> captures to see what the reported ranges are). >> >> Could everybody who is responsible for a demod please take a look at >> the list and see if you can fill in the holes? >> >> Having a definitive list of the current state is important to being >> able to provide unified reporting of SNR. >> >> Thank you, >> >> Devin >> > >> mt312.c unknown > > The hardware provides two values: > * AGC: For now the AGC feedback value (14 bit) is returned unchanged. > * ERR_db: Also available is a 10-bit value representing the signal level > difference between AGC-Reference and received signal level (most likely in > 1dB steps). > > If an absolute value is needed: I don't get it how to calc absolute signal > levels from AGC-Reference. > > so code for now: > mt312.c: agc-feedback 0-0x3FFF > > @Obi: > Any additions? >>From the manual: 7.2.3 Measured Signal to Noise Ratio. Registers 9 - 10 (R) M SNR[14:0]: These two registers provide a indication of the signal to noise ratio of the channel being received by the MT312. It should not be taken as the absolute value of the SNR. Eb/N0 = ~ (13312 - M_SNR[14:0] / 683) dB. The equation given only holds for Es/No values in the range 3 to 15 dB, i.e. Eb/No values in the range 0 to 12 dB. Regards, Andreas _______________________________________________ linux-dvb mailing list linux-dvb@linuxtv.org http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb