From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751408AbZHaHlc (ORCPT ); Mon, 31 Aug 2009 03:41:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751298AbZHaHlb (ORCPT ); Mon, 31 Aug 2009 03:41:31 -0400 Received: from smtp-vbr4.xs4all.nl ([194.109.24.24]:3068 "EHLO smtp-vbr4.xs4all.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751210AbZHaHla (ORCPT ); Mon, 31 Aug 2009 03:41:30 -0400 X-Greylist: delayed 467 seconds by postgrey-1.27 at vger.kernel.org; Mon, 31 Aug 2009 03:41:30 EDT Message-ID: In-Reply-To: <200908310858.24763.laurent.pinchart@ideasonboard.com> References: <4A52E897.8000607@freemail.hu> <4A910C42.5000001@freemail.hu> <20090830234114.16b90c36@pedra.chehab.org> <200908310858.24763.laurent.pinchart@ideasonboard.com> Date: Mon, 31 Aug 2009 09:33:23 +0200 Subject: Re: [RESEND][PATCH 1/2] v4l2: modify the webcam video standard handling From: "Hans Verkuil" To: "Laurent Pinchart" Cc: "Mauro Carvalho Chehab" , =?iso-8859-1?Q?N=E9meth_M=E1rton?= , "Jean-Francois Moine" , "Thomas Kaiser" , linux-media@vger.kernel.org, "LKML" User-Agent: SquirrelMail/1.4.18 MIME-Version: 1.0 Content-Type: text/plain;charset=iso-8859-1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > Hi Mauro, > > On Monday 31 August 2009 04:41:14 Mauro Carvalho Chehab wrote: >> Hi Németh, >> >> Em Sun, 23 Aug 2009 11:30:42 +0200 >> >> Németh Márton escreveu: >> > From: Márton Németh >> > >> > Change the handling of the case when vdev->tvnorms == 0. >> >> This patch (together with a few others related to tvnorms and camera >> drivers) reopens an old discussion: should webcams report a tvnorm? >> >> There's no easy answer for it since: >> >> 1) removing support for VIDIOC_G_STD/VIDIOC_S_STD causes regressions, >> since >> some userspace apps stops working; > > Then those applications don't work with the uvcvideo driver in the first > place. This is getting less and less common :-) > >> 2) It is a common scenario to use cameras connected to some capture only >> devices like several bttv boards used on surveillance systems. Those >> drivers report STD, since they are used also on TV; >> >> 3) There are even some devices that allows cameras to be connected to >> one >> input and TV on another input. This is another case were the driver will >> report a TV std; > > TV standards are ill-named, they are actually analog standards. > VIDIOC_[GS]_STD are perfectly valid for capture devices with analog > inputs, > even if they don't use a TV tuner. > >> 4) Most webcam formats are based on ITU-T formats designed to be >> compatible >> with TV (formats like CIF and like 640x480 - and their >> multiple/sub-multiples); > > Even HD formats still have roots in the analog TV world. It's a real mess. > Nonetheless, even if the actual frame size is compatible with TV, there is > simply no concept of PAL/NTSC for webcams. > >> 5) There are formats that weren't originated from TV on some digital >> webcams, so, for those formats, it makes no sense to report an existing >> std. >> >> Once people proposed to create an special format for those cases >> (V4L2_STD_DIGITAL or something like that), but, after lots of >> discussions, >> no changes were done at API nor at the drivers. > > TV standards only apply to analog video. Let's simply not use it for > digital > video. We don't expect drivers to implement VIDIOC_[GS]_JPEGCOMP with fake > values when they don't support JPEG compression, so we should not expect > them > to implement VIDIOC_[GS]_STD when they don't support analog TV. Exactly. Work is underway to add an API for HDTV and similar digital video formats. But we should just freeze the v4l2_std_id API and only use it for the analog PAL/NTSC/SECAM type formats. This nicely corresponds with the underlying standards as those have been frozen as well. Regards, Hans > >> While we don't have an agreement on this, I don't think we should apply >> a >> patch like this. > > -- > Regards, > > Laurent Pinchart > -- > To unsubscribe from this list: send the line "unsubscribe linux-media" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Hans Verkuil - video4linux developer - sponsored by TANDBERG