From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from poutre.nerim.net ([62.4.16.124]:59914 "EHLO poutre.nerim.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752233AbZJWPrE (ORCPT ); Fri, 23 Oct 2009 11:47:04 -0400 Received: from localhost (localhost [127.0.0.1]) by poutre.nerim.net (Postfix) with ESMTP id CD8E839DE7C for ; Fri, 23 Oct 2009 17:47:04 +0200 (CEST) Received: from poutre.nerim.net ([127.0.0.1]) by localhost (poutre.nerim.net [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id u1NVK+g+7jBy for ; Fri, 23 Oct 2009 17:47:03 +0200 (CEST) Received: from hyperion.delvare (jdelvare.pck.nerim.net [62.212.121.182]) by poutre.nerim.net (Postfix) with ESMTP id D334B39DC36 for ; Fri, 23 Oct 2009 17:47:03 +0200 (CEST) Date: Fri, 23 Oct 2009 17:47:05 +0200 From: Jean Delvare To: LMML Subject: Re: Details about DVB frontend API Message-ID: <20091023174705.7db4db52@hyperion.delvare> In-Reply-To: <20091022211330.6e84c6e7@hyperion.delvare> References: <20091022211330.6e84c6e7@hyperion.delvare> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On Thu, 22 Oct 2009 21:13:30 +0200, Jean Delvare wrote: > For example, the signal strength. All I know so far is that this is a > 16-bit value. But then what? Do greater values represent stronger > signal or weaker signal? Are 0x0000 and 0xffff special values? Is the > returned value meaningful even when FE_HAS_SIGNAL is 0? When > FE_HAS_LOCK is 0? Is the scale linear, or do some values have > well-defined meanings, or is it arbitrary and each driver can have its > own scale? What are the typical use cases by user-space application for > this value? To close the chapter on signal strength... I understand now that we don't have strict rules about the exact values. But do we have at least a common agreement that greater values mean stronger signal? I am asking because the DVB-T adapter model I have here behaves very strangely in this respect. I get values of: * 0xffff when there's no signal at all * 0x2828 to 0x2e2e when signal is OK * greater values as signal weakens (I have an amplified antenna with manual gain control) up to 0x7272 I would have expected it the other way around: 0x0000 for no signal and greater values as signal strengthens. I think the frontend driver (cx22702) needs to be fixed. -- Jean Delvare