[{"id":38121,"web_url":"https://patchwork.libcamera.org/comment/38121/","msgid":"<177039184628.607498.1382127475085964976@neptunite.rasen.tech>","date":"2026-02-06T15:30:46","subject":"Re: [PATCH v3 07/19] ipa: camera_sensor_helper: Introduce\n\tminFrameDuration()","submitter":{"id":17,"url":"https://patchwork.libcamera.org/api/people/17/","name":"Paul Elder","email":"paul.elder@ideasonboard.com"},"content":"Quoting Jacopo Mondi (2025-11-14 23:17:02)\n> After having introduced CameraSensorHelper::maxShutterTime() which\n> calculates the maximum shutter time which can be achieved given\n> a frame duration, this patch introduces the opposite operation, that\n> given a desired shutter time calculates what is the minimum frame\n> duration required to achieve it.\n> \n> The intended users of this function are IPA modules that after having\n> calculated a new exposure time need to regulate the frame duration to\n> achieve it.\n> \n> Signed-off-by: Jacopo Mondi \n> ---\n> src/ipa/libipa/camera_sensor_helper.cpp | 33 +++++++++++++++++++++++++++++++++\n> src/ipa/libipa/camera_sensor_helper.h | 2 ++\n> 2 files changed, 35 insertions(+)\n> \n> diff --git a/src/ipa/libipa/camera_sensor_helper.cpp b/src/ipa/libipa/camera_sensor_helper.cpp\n> index 3c3e24c1cdefa4bca059352482bb29654a37b42f..a38f1eb40446b98a0db4642f086742674a13854f 100644\n> --- a/src/ipa/libipa/camera_sensor_helper.cpp\n> +++ b/src/ipa/libipa/camera_sensor_helper.cpp\n> @@ -184,6 +184,39 @@ utils::Duration CameraSensorHelper::maxShutterTime(utils::Duration maxFrameDurat\n> return maxFrameDuration - exposureMargin * lineDuration;\n> }\n> \n> +/**\n> + * \\brief Compute the minimum frame duration required for a desired exposure\n> + * \\param[in] shutterTime The shutter time\n> + * \\param[in] lineDuration The current sensor line duration\n> + *\n> + * This function returns the minimum frame duration required to achieve the\n> + * desired \\a shutterTime. The frame duration is calculated by adding to\n> + * \\a shutterTime the difference between the frame length and the maximum\n> + * achievable integration time.\n> + *\n> + * The intended users of this function are IPA modules that want to calculate\n> + * the minium required frame duration give a newly calculated shutter time.\n\ns/minium/minimum/\n\ns/give/given/\n\nOtherwise, looks good to me.\n\nReviewed-by: Paul Elder \n\n> + *\n> + * \\todo The line duration should be a property of the CameraSensorHelper class\n> + * instead of being provided by the IPA.\n> + *\n> + * \\return The minimum frame duration required to achieve the desired shutter\n> + * time\n> + */\n> +utils::Duration CameraSensorHelper::minFrameDuration(utils::Duration shutterTime,\n> + utils::Duration lineDuration) const\n> +{\n> + /* Use a static to rate-limit the error message. */\n> + static uint32_t exposureMargin = exposureMargin_.has_value()\n> + ? exposureMargin_.value() : 0;\n> + if (!exposureMargin_.has_value() && !exposureMargin) {\n> + LOG(CameraSensorHelper, Warning)\n> + << \"Exposure margin not known. Default to 4\";\n> + exposureMargin = 4;\n> + }\n> +\n> + return shutterTime + exposureMargin * lineDuration;\n> +}\n> /**\n> * \\struct CameraSensorHelper::AnalogueGainLinear\n> * \\brief Analogue gain constants for the linear gain model\n> diff --git a/src/ipa/libipa/camera_sensor_helper.h b/src/ipa/libipa/camera_sensor_helper.h\n> index a1cf4bc334ad3b9a51d26b345bd5f0630c7ae87c..e9b53f183e8e6d305b50b5f3b46dc0199efee018 100644\n> --- a/src/ipa/libipa/camera_sensor_helper.h\n> +++ b/src/ipa/libipa/camera_sensor_helper.h\n> @@ -33,6 +33,8 @@ public:\n> double quantizeGain(double gain, double *quantizationGain) const;\n> utils::Duration maxShutterTime(utils::Duration maxFrameDuration,\n> utils::Duration lineDuration) const;\n> + utils::Duration minFrameDuration(utils::Duration exposureTime,\n> + utils::Duration lineDuration) const;\n> \n> protected:\n> struct AnalogueGainLinear {\n> \n> -- \n> 2.51.1\n>","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 1EC93C32EA\n\tfor ;\n\tFri, 6 Feb 2026 15:30:54 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 85354620A5;\n\tFri, 6 Feb 2026 16:30:53 +0100 (CET)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 25A686209B\n\tfor ;\n\tFri, 6 Feb 2026 16:30:52 +0100 (CET)","from neptunite.rasen.tech (unknown\n\t[IPv6:2404:7a81:160:2100:5247:7b72:2b7:10da])\n\tby perceval.ideasonboard.com (Postfix) with UTF8SMTPSA id 09FF814C7; \n\tFri, 6 Feb 2026 16:30:07 +0100 (CET)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"irmtPAvY\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1770391808;\n\tbh=1uKyrpCeDA1YPVkDNh60g1dGcXTPRebCCB9YLunZdn0=;\n\th=In-Reply-To:References:Subject:From:Cc:To:Date:From;\n\tb=irmtPAvYPMziLbyZYKzfV7o8RkIgQF8cwYGTWNqcdJomUaFJwHyMGSKYjtrgEkGwx\n\taKjjS1iutPDcpQBCoEiWItd9bjWsyqb5ptBhAh4JfYQXlE5jca9EWLYe3iGv8Tn5TO\n\tZ7BfV3qQ6V9xqePo6E9LmFYynO+axiatOgpTTNzA=","Content-Type":"text/plain; charset=\"utf-8\"","MIME-Version":"1.0","Content-Transfer-Encoding":"quoted-printable","In-Reply-To":"<20251114-exposure-limits-v3-7-b7c07feba026@ideasonboard.com>","References":"<20251114-exposure-limits-v3-0-b7c07feba026@ideasonboard.com>\n\t<20251114-exposure-limits-v3-7-b7c07feba026@ideasonboard.com>","Subject":"Re: [PATCH v3 07/19] ipa: camera_sensor_helper: Introduce\n\tminFrameDuration()","From":"Paul Elder ","Cc":"Jacopo Mondi ","To":"Jacopo Mondi , Niklas =?utf-8?b?U8O2?=\n\t=?utf-8?q?derlund?= , Robert Mader\n\t, libcamera-devel@lists.libcamera.org","Date":"Sat, 07 Feb 2026 00:30:46 +0900","Message-ID":"<177039184628.607498.1382127475085964976@neptunite.rasen.tech>","User-Agent":"alot/0.0.0","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\" "}}]