From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]:9602 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752698Ab2GEUKr (ORCPT ); Thu, 5 Jul 2012 16:10:47 -0400 Message-ID: <4FF5F4C4.7080904@redhat.com> Date: Thu, 05 Jul 2012 17:10:44 -0300 From: Mauro Carvalho Chehab MIME-Version: 1.0 To: Bert Massop CC: linux-media@vger.kernel.org Subject: Re: [PATCH 3/3] [media] tuner, xc2028: add support for get_afc() References: <1341497792-6066-1-git-send-email-mchehab@redhat.com> <1341497792-6066-3-git-send-email-mchehab@redhat.com> <4FF5AD40.3070707@iki.fi> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: Em 05-07-2012 14:37, Bert Massop escreveu: > On Thu, Jul 5, 2012 at 5:05 PM, Antti Palosaari wrote: >> >> On 07/05/2012 05:16 PM, Mauro Carvalho Chehab wrote: >>> >>> Implement API support to return AFC frequency shift, as this device >>> supports it. The only other driver that implements it is tda9887, >>> and the frequency there is reported in Hz. So, use Hz also for this >>> tuner. >> >> >> What is AFC and why it is needed? >> > > AFC is short for Automatic Frequency Control, by which a tuner > automatically fine-tunes the frequency for the best reception, > compensating for small offsets and oscillator frequency drift. > This is however done automatically on the tuner, so its configuration > is read-only. Aside from being a "nice to know" statistic, getting > hold of the AFC frequency shift does as far as I know not have any > practical uses related to properly operating the tuner. AFC might be useful on a few situations. For example, my CATV operator still broadcasts some channels in both analog and digital. The analog equipment there doesn't seem to be well-maintained, as some channels have frequency shifts or have some other artifacts. Still, analog broadcast is useful for me to test drivers ;) Anyway, adjusting the channel tables to consider that offset shift help to tune them a little faster and/or get a better quality by letting the PLL to work closer to the pilot carrier. Regards, Mauro