From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from smtp-68.nebula.fi ([83.145.220.68]:46940 "EHLO smtp-68.nebula.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932254Ab2AKWgV (ORCPT ); Wed, 11 Jan 2012 17:36:21 -0500 Date: Thu, 12 Jan 2012 00:36:16 +0200 From: Sakari Ailus To: Sylwester Nawrocki Cc: Laurent Pinchart , "HeungJun, Kim" , linux-media@vger.kernel.org, mchehab@redhat.com, hverkuil@xs4all.nl, kyungmin.park@samsung.com, Hans de Goede , Luca Risolia Subject: Re: [RFC PATCH 1/4] v4l: Add V4L2_CID_PRESET_WHITE_BALANCE menu control Message-ID: <20120111223616.GT9323@valkosipuli.localdomain> References: <1325053428-2626-1-git-send-email-riverful.kim@samsung.com> <4F007DED.4070201@gmail.com> <20120104203933.GJ9323@valkosipuli.localdomain> <201201042157.17040.laurent.pinchart@ideasonboard.com> <4F04C394.5050302@iki.fi> <4F04CD55.2000500@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4F04CD55.2000500@gmail.com> Sender: linux-media-owner@vger.kernel.org List-ID: On Wed, Jan 04, 2012 at 11:06:13PM +0100, Sylwester Nawrocki wrote: > Hi Sakari, > > On 01/04/2012 10:24 PM, Sakari Ailus wrote: > >>>>> I don't quite understand the purpose of the do_white_balance; the > >>>>> automatic white balance algorithm is operational until it's disabled, > >>>>> and after disabling it the white balance shouldn't change. What is the > >>>>> extra functionality that the do_white_balance control implements? > >>>> > >>>> Maybe DO_WHITE_BALANCE was inspired by some hardware's behaviour, I don't > >>>> know. I have nothing against this control. It allows you to perform > >>>> one-shot white balance in a given moment in time. Simple and clear. > >>> > >>> Well, yes, if you have an automatic white balance algorithm which supports > >>> "one-shot" mode. Typically it's rather a feedback loop. I guess this means > >>> "just run one iteration". > >>> > >>> Something like this should possibly be used to get the white balance > >>> correct by pointing the camera to an object of known colour (white > >>> typically, I think). But this isn't it, at least based on the description > >>> in the spec. > >> > >> Then either the spec is incorrect, or I'm mistaken. My understanding of the > >> DO_WHITE_BALANCE control is exactly what you described. > > > > This is what the spec says: > > > > "This is an action control. When set (the value is ignored), the device will do > > a white balance and then hold the current setting. Contrast this with the > > boolean V4L2_CID_AUTO_WHITE_BALANCE, which, when activated, keeps adjusting the > > white balance." > > > > I wonder if that should be then changed --- or is it just me who got a different > > idea from the above description? > > Only you ? :-) Same as Laurent, I understood this control can be used to do white > balance after pointing camera to a white object. Not sure if the description > needs to be changed. Definitely it needs to be changed. Who will submit the patch? :-) -- Sakari Ailus e-mail: sakari.ailus@iki.fi jabber/XMPP/Gmail: sailus@retiisi.org.uk