{"id":27472,"url":"https://patchwork.libcamera.org/api/patches/27472/?format=json","web_url":"https://patchwork.libcamera.org/patch/27472/","project":{"id":1,"url":"https://patchwork.libcamera.org/api/projects/1/?format=json","name":"libcamera","link_name":"libcamera","list_id":"libcamera_core","list_email":"libcamera-devel@lists.libcamera.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20260723154327.1357866-23-barnabas.pocze@ideasonboard.com>","date":"2026-07-23T15:43:05","name":"[RFC,v2,22/43] ipa: libipa: agc: Clamp exposure value","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"1ab20c7b9e34cdeb65d326df69891bf8cde9609c","submitter":{"id":216,"url":"https://patchwork.libcamera.org/api/people/216/?format=json","name":"Barnabás Pőcze","email":"barnabas.pocze@ideasonboard.com"},"delegate":null,"mbox":"https://patchwork.libcamera.org/patch/27472/mbox/","series":[{"id":6075,"url":"https://patchwork.libcamera.org/api/series/6075/?format=json","web_url":"https://patchwork.libcamera.org/project/libcamera/list/?series=6075","date":"2026-07-23T15:42:43","name":"ipa: libipa: agc rework","version":2,"mbox":"https://patchwork.libcamera.org/series/6075/mbox/"}],"comments":"https://patchwork.libcamera.org/api/patches/27472/comments/","check":"pending","checks":"https://patchwork.libcamera.org/api/patches/27472/checks/","tags":{},"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 AF2BFC3308\n\tfor ;\n\tThu, 23 Jul 2026 15:44:07 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 468C867F1D;\n\tThu, 23 Jul 2026 17:44:07 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id EEB0967EC5\n\tfor ;\n\tThu, 23 Jul 2026 17:43:35 +0200 (CEST)","from pb-laptop.local (185.182.215.156.nat.pool.zt.hu\n\t[185.182.215.156])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 19DDC1C37\n\tfor ;\n\tThu, 23 Jul 2026 17:42:35 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"aLtw0KBf\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1784821355;\n\tbh=r7fms7akk/zwjiuHiG6GIK0QnaIjwx2y4+nqZtRnBa0=;\n\th=From:To:Subject:Date:In-Reply-To:References:From;\n\tb=aLtw0KBfP2ruDa9VtCeEq4d5CQDtK04I2K0TWomdy9Y4VBCUFqxSnhnqLVvlEOnuK\n\tj4pCnd4ycj2qQ0EbgVIuB7rQoK+/waRpmbrSvc9DxDbWibEx+ubdtGJUHY06eMo+Lk\n\t4A6eF6hZvmDXvpP3HGb1HQ8ZWTQGBefSvFsl2TlQ=","From":"=?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= ","To":"libcamera-devel@lists.libcamera.org","Subject":"[RFC PATCH v2 22/43] ipa: libipa: agc: Clamp exposure value","Date":"Thu, 23 Jul 2026 17:43:05 +0200","Message-ID":"<20260723154327.1357866-23-barnabas.pocze@ideasonboard.com>","X-Mailer":"git-send-email 2.55.0","In-Reply-To":"<20260723154327.1357866-1-barnabas.pocze@ideasonboard.com>","References":"<20260723154327.1357866-1-barnabas.pocze@ideasonboard.com>","MIME-Version":"1.0","Content-Type":"text/plain; charset=UTF-8","Content-Transfer-Encoding":"8bit","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\" "},"content":"It is possible that the minimum exposure time in microseconds is not an\ninteger. In that case the minimum `ExposureTime` in the `ControlInfo` will\ntherefore be actually lower than the real minimum. This can cause issues:\nif the minimum published exposure time is set, the division when setting\n`agc.manual.exposure` might produce a value in [0;1), leading to the manual\nexposure being set to 0, leading to an assertion failure in\n`ExposureModeHelper::splitExposure()`.\n\nNote that this is theoretically possible even when the exposure time is\ndetermined automatically by `AgcMeanLuminance`.\n\nStore the true integer limits of the exposure as well, and ensure that\nthe exposure (time) -> exposure (line) conversions always clamp.\n\nSigned-off-by: Barnabás Pőcze \n---\n src/ipa/libipa/agc.cpp | 27 ++++++++++++++++++++++++---\n src/ipa/libipa/agc.h | 2 ++\n 2 files changed, 26 insertions(+), 3 deletions(-)","diff":"diff --git a/src/ipa/libipa/agc.cpp b/src/ipa/libipa/agc.cpp\nindex e16a02fdde..8a2525ec98 100644\n--- a/src/ipa/libipa/agc.cpp\n+++ b/src/ipa/libipa/agc.cpp\n@@ -38,6 +38,12 @@ LOG_DEFINE_CATEGORY(Agc)\n * \\struct agc::Session\n * \\brief Session configuration for AgcAlgorithm\n *\n+ * \\var agc::Session::minExposure\n+ * \\brief Minimum exposure (in lines) supported with the configured sensor\n+ *\n+ * \\var agc::Session::maxExposure\n+ * \\brief Maximum exposure (in lines) supported with the configured sensor\n+ *\n * \\var agc::Session::minExposureTime\n * \\brief Minimum exposure time supported with the configured sensor\n *\n@@ -223,6 +229,19 @@ LOG_DEFINE_CATEGORY(Agc)\n * \\brief Effective lux value of the frame\n */\n \n+namespace {\n+\n+[[nodiscard]] uint32_t clampExposure(utils::Duration exposureTime, const agc::Session &session)\n+{\n+\treturn std::clamp(\n+\t\texposureTime / session.lineDuration,\n+\t\tsession.minExposure,\n+\t\tsession.maxExposure\n+\t);\n+}\n+\n+} /* namespace */\n+\n /**\n * \\brief Load tuning data\n */\n@@ -317,6 +336,8 @@ int AgcAlgorithm::configure(agc::Session &session, agc::ActiveState &state, cons\n \t *\n \t * \\todo take VBLANK into account for maximum exposure time\n \t */\n+\tsession.minExposure = minExposure;\n+\tsession.maxExposure = maxExposure;\n \tsession.minExposureTime = minExposure * session.lineDuration;\n \tsession.maxExposureTime = maxExposure * session.lineDuration;\n \tsession.minAnalogueGain = minGain;\n@@ -331,7 +352,7 @@ int AgcAlgorithm::configure(agc::Session &session, agc::ActiveState &state, cons\n \t/* Configure the default exposure and gain. */\n \tstate = {};\n \tstate.automatic.gain = session.minAnalogueGain;\n-\tstate.automatic.exposure = 10ms / session.lineDuration;\n+\tstate.automatic.exposure = clampExposure(10ms, session);\n \tstate.automatic.quantizationGain = 1;\n \tstate.automatic.yTarget = impl_.effectiveYTarget(0, 1);\n \tstate.manual.gain = state.automatic.gain;\n@@ -437,7 +458,7 @@ void AgcAlgorithm::queueRequest(const agc::Session &session, agc::ActiveState &s\n \n \tconst auto &exposure = controls.get(controls::ExposureTime);\n \tif (exposure && !state.autoExposureEnabled) {\n-\t\tstate.manual.exposure = *exposure * 1.0us / session.lineDuration;\n+\t\tstate.manual.exposure = clampExposure(*exposure * 1us, session);\n \n \t\tLOG(Agc, Debug)\n \t\t\t<< \"Set exposure to \" << state.manual.exposure;\n@@ -599,7 +620,7 @@ void AgcAlgorithm::process(const agc::Session &session, agc::ActiveState &state,\n \t\t\t<< \", \" << newEv.quantizationGain << \" and \" << newEv.digitalGain;\n \n \t\t/* Update the estimated exposure and gain. */\n-\t\tstate.automatic.exposure = newEv.exposureTime / lineDuration;\n+\t\tstate.automatic.exposure = clampExposure(newEv.exposureTime, session);\n \t\tstate.automatic.gain = newEv.analogueGain;\n \t\tstate.automatic.quantizationGain = newEv.quantizationGain;\n \t\tstate.automatic.yTarget = newEv.yTarget;\ndiff --git a/src/ipa/libipa/agc.h b/src/ipa/libipa/agc.h\nindex 1eace12908..c11dbf80cd 100644\n--- a/src/ipa/libipa/agc.h\n+++ b/src/ipa/libipa/agc.h\n@@ -49,6 +49,8 @@ prepareControls(ControlList &controls, const CameraSensorHelper *sensor,\n }\n \n struct Session {\n+\tuint32_t minExposure;\n+\tuint32_t maxExposure;\n \tutils::Duration minExposureTime;\n \tutils::Duration maxExposureTime;\n \tdouble minAnalogueGain;\n","prefixes":["RFC","v2","22/43"]}