{"id":25624,"url":"https://patchwork.libcamera.org/api/1.1/patches/25624/?format=json","web_url":"https://patchwork.libcamera.org/patch/25624/","project":{"id":1,"url":"https://patchwork.libcamera.org/api/1.1/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":"<20260105-softisp-agc-v2-1-9013e693ffd5@mainlining.org>","date":"2026-01-05T12:41:35","name":"[v2] ipa: simple: fix minimal analog gain init","commit_ref":null,"pull_url":null,"state":"superseded","archived":false,"hash":"d7a89ad8e7b3236cd683660548f7a84a0f3e299f","submitter":{"id":255,"url":"https://patchwork.libcamera.org/api/1.1/people/255/?format=json","name":"Vasiliy Doylov","email":"nekocwd@mainlining.org"},"delegate":null,"mbox":"https://patchwork.libcamera.org/patch/25624/mbox/","series":[{"id":5683,"url":"https://patchwork.libcamera.org/api/1.1/series/5683/?format=json","web_url":"https://patchwork.libcamera.org/project/libcamera/list/?series=5683","date":"2026-01-05T12:41:35","name":"[v2] ipa: simple: fix minimal analog gain init","version":2,"mbox":"https://patchwork.libcamera.org/series/5683/mbox/"}],"comments":"https://patchwork.libcamera.org/api/patches/25624/comments/","check":"pending","checks":"https://patchwork.libcamera.org/api/patches/25624/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 0BA68BDCBF\n\tfor ;\n\tMon, 5 Jan 2026 12:41:39 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id D94FA61FBF;\n\tMon, 5 Jan 2026 13:41:37 +0100 (CET)","from mail.mainlining.org (mail.mainlining.org [5.75.144.95])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 437EA61F35\n\tfor ;\n\tMon, 5 Jan 2026 13:41:36 +0100 (CET)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (2048-bit key;\n\tunprotected) header.d=mainlining.org header.i=@mainlining.org\n\theader.b=\"gxdN1j6R\"; \n\tdkim=permerror (0-bit key) header.d=mainlining.org\n\theader.i=@mainlining.org header.b=\"LJG+v2d+\"; \n\tdkim-atps=neutral","DKIM-Signature":["v=1; a=rsa-sha256; s=202507r; d=mainlining.org;\n\tc=relaxed/relaxed; \n\th=To:Message-Id:Subject:Date:From; t=1767616895;\n\tbh=YHjvv4w3CRFhovlni3IRLXD OklS5XYPkV8hcn+7u9ug=;\n\tb=gxdN1j6RRdj0pLpP1PlH+47V6VIfXuuKD+O8xt5YFWkchsC/uA\n\tb7NAnWWYCZK9mVJ057VO1u9SpBnqGCLdBrX5VzDDH/AFPDYOWT9KohqmWAlYEDQRQOCADLtYIKZ\n\t6YuRySTvCm3o3xBan7RXpylsi36JFGfxs2SSiCBnhxk0Bv9I2LxNuAt7O4L3oWAahIoTGdNziou\n\tkrK0TuTWaAThSIMDAk10recOP+Q34QcLJ1fILAjYiVKbV3D9gY0a0JcDzo6up3XgONsEuEaWMtc\n\tnY+aTyEUSeUuuqRaWNZtrgoRvpDlwasiDFefenuN84ywCIQ1PJQjmDrpeSISykOMFJA==;","v=1; a=ed25519-sha256; s=202507e; d=mainlining.org;\n\tc=relaxed/relaxed; \n\th=To:Message-Id:Subject:Date:From; t=1767616895;\n\tbh=YHjvv4w3CRFhovlni3IRLXD OklS5XYPkV8hcn+7u9ug=;\n\tb=LJG+v2d+0s2/1ibRPtx6GJCtCNwTn5C4a6tQEu3S4QHau/Q4cs\n\tu/gfhKNjvp4b3oNn/HUdVjISTtQsMPyYT7Bw==;"],"From":"Vasiliy Doylov ","Date":"Mon, 05 Jan 2026 15:41:35 +0300","Subject":"[PATCH v2] ipa: simple: fix minimal analog gain init","MIME-Version":"1.0","Content-Type":"text/plain; charset=\"utf-8\"","Content-Transfer-Encoding":"7bit","Message-Id":"<20260105-softisp-agc-v2-1-9013e693ffd5@mainlining.org>","X-B4-Tracking":"v=1; b=H4sIAH6xW2kC/23MQQ7CIBCF4as0s3YMUKHqynuYLhAonUShgYZoG\n\tu4udu3yf8n7Nsgukctw7TZIrlCmGFqIQwdm1sE7JNsaBBOKcSYxx2mlvKD2BrmyjJtHb/XpAu2\n\txJDfRe9fuY+uZ8hrTZ8cL/63/ncKR4zAooSSTZ9nr20tTeFKg4I8xeRhrrV8dsD6DqwAAAA==","X-Change-ID":"20260105-softisp-agc-16d01cb3da49","To":"libcamera-devel@lists.libcamera.org","Cc":"Vasiliy Doylov ","X-Mailer":"b4 0.14.3","X-Developer-Signature":"v=1; a=openpgp-sha256; l=2204;\n\ti=nekocwd@mainlining.org; h=from:subject:message-id;\n\tbh=s8L2NzmuwKOGjyJ/vr3euP0ERdEOlXZdojkxgKWJNDA=;\n\tb=owGbwMvMwCXGd//xporA/cmMp9WSGDKjN9YH6K7/r/DDO/LT59jOiApelutOXg95A/5on8+p4\n\tfzJXXeho5SFQYyLQVZMkeW/4SK5AzeUPetyU5/BzGFlAhnCwMUpABPJC2T4H11vuVZt28yXzLYT\n\tyoJ39hiI5p/TeK/Cp+R4NN/SKHLxSYb//g4SSzXUJtQHJKt+PXtA4nnGsfmJrVpzNi3uTbjds/4\n\tzDwA=","X-Developer-Key":"i=nekocwd@mainlining.org; a=openpgp;\n\tfpr=FF31A21EC0D823497E6D65E60EDFE3B27851BF63","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":"On most imx sensors the formula seems to be:\n\nagain_float = 512.0 / (512.0 - again_ctrl_value)\n\nSo the default of 0 makes sense and actually translates to a gain of 1.0.\nAnd the max gain of 400 leads to 512.0 / 112.0 = 4.57 which is about typical for\na max sensor gain.\n\nSigned-off-by: Vasiliy Doylov \n---\nChanges in v2:\n- Drop old solution\n- Fix minimal analog gain initialisation\n- Link to v1: https://lists.libcamera.org/pipermail/libcamera-devel/2026-January/056045.html\n---\n src/ipa/simple/soft_simple.cpp | 19 +------------------\n 1 file changed, 1 insertion(+), 18 deletions(-)\n\n\n---\nbase-commit: 2861817f09c96a0660b88783eff159631e42030f\nchange-id: 20260105-softisp-agc-16d01cb3da49\n\nBest regards,","diff":"diff --git a/src/ipa/simple/soft_simple.cpp b/src/ipa/simple/soft_simple.cpp\nindex b147aca2..dde11666 100644\n--- a/src/ipa/simple/soft_simple.cpp\n+++ b/src/ipa/simple/soft_simple.cpp\n@@ -237,26 +237,9 @@ int IPASoftSimple::configure(const IPAConfigInfo &configInfo)\n \t\t\t\tcamHelper_->blackLevel().value() / 256;\n \t\t}\n \t} else {\n-\t\t/*\n-\t\t * The camera sensor gain (g) is usually not equal to the value written\n-\t\t * into the gain register (x). But the way how the AGC algorithm changes\n-\t\t * the gain value to make the total exposure closer to the optimum\n-\t\t * assumes that g(x) is not too far from linear function. If the minimal\n-\t\t * gain is 0, the g(x) is likely to be far from the linear, like\n-\t\t * g(x) = a / (b * x + c). To avoid unexpected changes to the gain by\n-\t\t * the AGC algorithm (abrupt near one edge, and very small near the\n-\t\t * other) we limit the range of the gain values used.\n-\t\t */\n \t\tcontext_.configuration.agc.againMax = againMax;\n \t\tcontext_.configuration.agc.again10 = againDef;\n-\t\tif (againMin) {\n-\t\t\tcontext_.configuration.agc.againMin = againMin;\n-\t\t} else {\n-\t\t\tLOG(IPASoft, Warning)\n-\t\t\t\t<< \"Minimum gain is zero, that can't be linear\";\n-\t\t\tcontext_.configuration.agc.againMin =\n-\t\t\t\tstd::min(100, againMin / 2 + againMax / 2);\n-\t\t}\n+\t\tcontext_.configuration.agc.againMin = againMin;\n \t\tcontext_.configuration.agc.againMinStep = 1.0;\n \t}\n \n","prefixes":["v2"]}