From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.kapsi.fi ([217.30.184.167]:33650 "EHLO mail.kapsi.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750834Ab3AQRWo (ORCPT ); Thu, 17 Jan 2013 12:22:44 -0500 Message-ID: <50F8333E.2020904@iki.fi> Date: Thu, 17 Jan 2013 19:22:06 +0200 From: Antti Palosaari MIME-Version: 1.0 To: Manu Abraham CC: Mauro Carvalho Chehab , Simon Farnsworth , Linux Media Mailing List Subject: Re: [PATCH RFCv10 00/15] DVB QoS statistics API References: <1358217061-14982-1-git-send-email-mchehab@redhat.com> <20130116152151.5461221c@redhat.com> <2817386.vHx2V41lNt@f17simon> <20130116200153.3ec3ee7d@redhat.com> <50F7C57A.6090703@iki.fi> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On 01/17/2013 07:16 PM, Manu Abraham wrote: > On Thu, Jan 17, 2013 at 3:03 PM, Antti Palosaari wrote: >> On 01/17/2013 05:40 AM, Manu Abraham wrote: >>> MB86A20 is not the only demodulator driver with the Linux DVB. >>> And not all devices can output in dB scale proposed by you, But any device >>> output can be scaled in a relative way. So I don't see any reason why >>> userspace has to deal with cumbersome controls to deal with redundant >>> statistics, which is nonsense. >> >> >> What goes to these units in general, dB conversion is done by the driver >> about always. It is quite hard or even impossible to find out that formula >> unless you has adjustable test signal generator. >> >> Also we could not offer always dBm as signal strength. This comes to fact >> that only recent silicon RF-tuners are able to provide RF strength. More >> traditionally that estimation is done by demod from IF/RF AGC, which leads >> very, very, rough estimation. > > What I am saying is that, rather than sticking to a dB scale, it would be > better to fit it into a relative scale, ie loose dB altogether and use only the > relative scale. With that approach any device can be fit into that convention. > Even with an unknown device, it makes it pretty easy for anyone to fit > into that > scale. All you need is a few trial runs to get maxima/minima. When there > exists only a single convention that is simple, it makes it more easier for > people to stick to that convention, rather than for people to not support it. That is true. I don't have really clear opinion whether to force all to one scale, or return dBm those which could and that dummy scale for the others. Maybe I will still vote for both relative and dBm. Shortly there is two possibilities: 1) support only relative scale 2) support both dBm and relative scale (with dBm priority) [3) support only dBm is not possible] regards Antti -- http://palosaari.fi/