[{"id":39758,"web_url":"https://patchwork.libcamera.org/comment/39758/","msgid":"","date":"2026-07-20T10:32:25","subject":"Re: [RFC PATCH v8 4/6] libcamera: shaders: Add LSC support","submitter":{"id":175,"url":"https://patchwork.libcamera.org/api/people/175/","name":"Bryan O'Donoghue","email":"bryan.odonoghue@linaro.org"},"content":"On 16/07/2026 23:25, Milan Zamazal wrote:\n> From: Xander Pronk \n> \n> Lens shading correction should be applied after black level\n> subtraction (in order to make the computations with meaningful values)\n> and before white balance (especially before white balance stats are\n> computed).\n> \n> Note that lens shading correction depends on temperature, which is\n> computed from the preceding, rather than current, frame (this is due to\n> how white balance is currently computed).\n> \n> The shaders are compiled on initialisation, while lens shading\n> correction can be enabled or disabled dynamically, using the\n> corresponding control. The whole correction in the shader is wrapped by\n> a conditional macro to be able to disable it and all the related\n> overheads if Lsc algorithm is not enabled at all.\n> \n> If Lsc algorithm is enabled, the correction is always applied, whether\n> the given control is enabled or not. If it is not, 1.0 multipliers are\n> expected to be provided. This is because lens shading correction is\n> supposed to be rarely switched off using the runtime control when Lsc\n> algorithm is enabled, e.g. only for demoing or debugging purposes.\n> We prefer accepting the performance penalty of applying a no-op\n> correction in such cases rather than disturbing GPU computation in the\n> regular flow by introducing a runtime `if'.\n> \n> Co-developed-by: Rick ten Wolde \n> Signed-off-by: Rick ten Wolde \n> Signed-off-by: Xander Pronk \n> Signed-off-by: Milan Zamazal \n> ---\nReviewed-by: Bryan O'Donoghue ","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 4611BBE080\n\tfor ;\n\tMon, 20 Jul 2026 10:32:30 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 38BD16614D;\n\tMon, 20 Jul 2026 12:32:29 +0200 (CEST)","from mail-ej1-x62c.google.com (mail-ej1-x62c.google.com\n\t[IPv6:2a00:1450:4864:20::62c])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 4415A66122\n\tfor ;\n\tMon, 20 Jul 2026 12:32:27 +0200 (CEST)","by mail-ej1-x62c.google.com with SMTP id\n\ta640c23a62f3a-c15c42a45adso560408766b.0\n\tfor ;\n\tMon, 20 Jul 2026 03:32:27 -0700 (PDT)","from [192.168.0.101] ([109.77.26.223])\n\tby smtp.gmail.com with ESMTPSA id\n\ta640c23a62f3a-c1705afecc3sm441519366b.24.2026.07.20.03.32.25\n\t(version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128);\n\tMon, 20 Jul 2026 03:32:26 -0700 (PDT)"],"Authentication-Results":"lancelot.ideasonboard.com; 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\n\tMon, 20 Jul 2026 03:32:26 -0700 (PDT)","Message-ID":"","Date":"Mon, 20 Jul 2026 11:32:25 +0100","MIME-Version":"1.0","User-Agent":"Mozilla Thunderbird","Subject":"Re: [RFC PATCH v8 4/6] libcamera: shaders: Add LSC support","To":"Milan Zamazal , libcamera-devel@lists.libcamera.org","Cc":"Xander Pronk ,\n\tHans de Goede ,\n\tLaurent Pinchart ,\n\tRick ten Wolde ","References":"<20260716222515.251464-1-mzamazal@redhat.com>\n\t\n\t<20260716222515.251464-5-mzamazal@redhat.com>","From":"Bryan O'Donoghue ","Content-Language":"en-GB","In-Reply-To":"<20260716222515.251464-5-mzamazal@redhat.com>","Content-Type":"text/plain; charset=UTF-8; format=flowed","Content-Transfer-Encoding":"7bit","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}}]