From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mailout2.w2.samsung.com ([211.189.100.12]:39016 "EHLO usmailout2.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751545Ab3KCAUC convert rfc822-to-8bit (ORCPT ); Sat, 2 Nov 2013 20:20:02 -0400 Received: from uscpsbgm2.samsung.com (u115.gpu85.samsung.co.kr [203.254.195.115]) by mailout2.w2.samsung.com (Oracle Communications Messaging Server 7u4-24.01(7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTP id <0MVN00CNPVLCVK80@mailout2.w2.samsung.com> for linux-media@vger.kernel.org; Sat, 02 Nov 2013 20:20:00 -0400 (EDT) Date: Sat, 02 Nov 2013 22:19:56 -0200 From: Mauro Carvalho Chehab To: CrazyCat , linux-media@vger.kernel.org Subject: Re: [PATCH] tda18271-fe: Fix dvb-c standard selection Message-id: <20131102221956.1e241d02@samsung.com> In-reply-to: <52756F4E.3030805@narod.ru> References: <5275690A.3080108@narod.ru> <20131102192112.1bc7bbc0@samsung.com> <52756F4E.3030805@narod.ru> MIME-version: 1.0 Content-type: text/plain; charset=UTF-8 Content-transfer-encoding: 8BIT Sender: linux-media-owner@vger.kernel.org List-ID: Em Sat, 02 Nov 2013 23:31:58 +0200 CrazyCat escreveu: > Mauro Carvalho Chehab пишет: > > This is wrong, as it breaks for 6MHz-spaced channels, like what's used > > in Brazil and Japan. > > > > What happens here is that, if the tuner uses a too wide lowpass filter, > > the interference will be higher at the demod, and it may not be able > > to decode. > > > > As the bandwidth is already estimated by the DVB frontend core, the > > tuners should be adjusted to get the closest filter for a given > > bandwidth. > > > > So, the driver is correct (and it is tested under 6MHz spaced channels). > > But usual applications only set cable standard (Annex A/C or B) and not set bandwidth. So for annex A/C default selected 6MHz ? Usual applications set the symbol rate, and symbol rate is easily converted into bandwidth. The DVB core does that. see dtv_set_frontend(): switch (c->delivery_system) { case SYS_ATSC: case SYS_DVBC_ANNEX_B: c->bandwidth_hz = 6000000; break; case SYS_DVBC_ANNEX_A: rolloff = 115; break; case SYS_DVBC_ANNEX_C: rolloff = 113; break; default: break; } if (rolloff) c->bandwidth_hz = (c->symbol_rate * rolloff) / 100; -- Cheers, Mauro