{"id":26649,"url":"https://patchwork.libcamera.org/api/patches/26649/?format=json","web_url":"https://patchwork.libcamera.org/patch/26649/","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":"<20260506221944.066FD1EA006B@mailuser.phl.internal>","date":"2026-05-06T21:46:28","name":"[v5,2/3] libcamera: software_isp: Normalize statistics sums to 8-bit","commit_ref":null,"pull_url":null,"state":"accepted","archived":false,"hash":"14ac6b111e409b665395fc252fe1c6296d901e20","submitter":{"id":261,"url":"https://patchwork.libcamera.org/api/people/261/?format=json","name":"Javier Tia","email":"floss@jetm.me"},"delegate":null,"mbox":"https://patchwork.libcamera.org/patch/26649/mbox/","series":[{"id":5913,"url":"https://patchwork.libcamera.org/api/series/5913/?format=json","web_url":"https://patchwork.libcamera.org/project/libcamera/list/?series=5913","date":"2026-05-06T21:45:28","name":"ipa: simple: Proportional AGC and statistics normalization","version":5,"mbox":"https://patchwork.libcamera.org/series/5913/mbox/"}],"comments":"https://patchwork.libcamera.org/api/patches/26649/comments/","check":"pending","checks":"https://patchwork.libcamera.org/api/patches/26649/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 4B35FC32F7\n\tfor ;\n\tWed, 6 May 2026 22:19:48 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id EEA1063021;\n\tThu, 7 May 2026 00:19:46 +0200 (CEST)","from fhigh-a6-smtp.messagingengine.com\n\t(fhigh-a6-smtp.messagingengine.com [103.168.172.157])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id C88C66301A\n\tfor ;\n\tThu, 7 May 2026 00:19:44 +0200 (CEST)","from phl-compute-02.internal (phl-compute-02.internal\n\t[10.202.2.42])\n\tby mailfhigh.phl.internal (Postfix) with ESMTP id 239EB1400104;\n\tWed, 6 May 2026 18:19:44 -0400 (EDT)","from phl-imap-07 ([10.202.2.97])\n\tby phl-compute-02.internal (MEProxy); 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charset=\"utf-8\"","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit","From":"Javier Tia ","To":"libcamera-devel@lists.libcamera.org","Date":"Wed, 06 May 2026 15:46:28 -0600","Subject":"[PATCH v5 2/3] libcamera: software_isp: Normalize statistics sums to\n\t8-bit","Cc":"mzamazal@redhat.com, barnabas.pocze@ideasonboard.com,\n\tkieran.bingham@ideasonboard.com","In-Reply-To":"<177810597783.688418.1631246733707368646@jetm.me>","References":"<177810597783.688418.1631246733707368646@jetm.me>","Message-Id":"<20260506221944.066FD1EA006B@mailuser.phl.internal>","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":"The SWSTATS_ACCUMULATE_LINE_STATS() macro divides the luminance value\nfor the histogram to normalize it to 8-bit range, but does not apply\nthe same normalization to the RGB sums. For 10-bit and 12-bit unpacked\nBayer formats this means the sums are accumulated at native bit depth\n(0-1023 or 0-4095 per pixel) while the AWB algorithm subtracts an\n8-bit black level from them, under-correcting by 4x or 16x\nrespectively.\n\nThis mismatch between the AWB's gain calculation (using incorrectly\nBLC-subtracted sums) and the debayer's correct normalized BLC\nsubtraction produces a visible color cast. For example, with the\nOV2740 sensor (10-bit, BLC=16), the under-subtraction skews R/G gain\nby ~9%.\n\nFix this by right-shifting the RGB sums in finishFrame() to normalize\nthem to 8-bit scale, matching the histogram and the 8-bit black level\nused by AWB. A per-format sumShift_ value is set in configure():\n0 for 8-bit and CSI-2 packed formats (already 8-bit), 2 for 10-bit,\nand 4 for 12-bit unpacked formats.\n\nSigned-off-by: Javier Tia \nReviewed-by: Milan Zamazal \nTested-by: Milan Zamazal \nReviewed-by: Barnabás Pőcze \nTested-by: Barnabás Pőcze \n---\n include/libcamera/internal/software_isp/swstats_cpu.h | 1 +\n src/libcamera/software_isp/swstats_cpu.cpp | 9 +++++++++\n 2 files changed, 10 insertions(+)","diff":"diff --git a/include/libcamera/internal/software_isp/swstats_cpu.h b/include/libcamera/internal/software_isp/swstats_cpu.h\nindex 802370bd..2dac6945 100644\n--- a/include/libcamera/internal/software_isp/swstats_cpu.h\n+++ b/include/libcamera/internal/software_isp/swstats_cpu.h\n@@ -116,6 +116,7 @@ private:\n \n \tunsigned int xShift_;\n \tunsigned int stride_;\n+\tunsigned int sumShift_;\n \n \tstd::vector stats_;\n \tSharedMemObject sharedStats_;\ndiff --git a/src/libcamera/software_isp/swstats_cpu.cpp b/src/libcamera/software_isp/swstats_cpu.cpp\nindex 5366e019..b40d3334 100644\n--- a/src/libcamera/software_isp/swstats_cpu.cpp\n+++ b/src/libcamera/software_isp/swstats_cpu.cpp\n@@ -362,6 +362,11 @@ void SwStatsCpu::finishFrame(uint32_t frame, uint32_t bufferId)\n \t\t\tfor (unsigned int j = 0; j < SwIspStats::kYHistogramSize; j++)\n \t\t\t\tsharedStats_->yHistogram[j] += s.yHistogram[j];\n \t\t}\n+\t\tif (sumShift_) {\n+\t\t\tsharedStats_->sum_.r() >>= sumShift_;\n+\t\t\tsharedStats_->sum_.g() >>= sumShift_;\n+\t\t\tsharedStats_->sum_.b() >>= sumShift_;\n+\t\t}\n \t}\n \n \tsharedStats_->valid = valid;\n@@ -425,12 +430,15 @@ int SwStatsCpu::configure(const StreamConfiguration &inputCfg, unsigned int stat\n \t\tswitch (bayerFormat.bitDepth) {\n \t\tcase 8:\n \t\t\tstats0_ = &SwStatsCpu::statsBGGR8Line0;\n+\t\t\tsumShift_ = 0;\n \t\t\treturn 0;\n \t\tcase 10:\n \t\t\tstats0_ = &SwStatsCpu::statsBGGR10Line0;\n+\t\t\tsumShift_ = 2;\n \t\t\treturn 0;\n \t\tcase 12:\n \t\t\tstats0_ = &SwStatsCpu::statsBGGR12Line0;\n+\t\t\tsumShift_ = 4;\n \t\t\treturn 0;\n \t\t}\n \t}\n@@ -442,6 +450,7 @@ int SwStatsCpu::configure(const StreamConfiguration &inputCfg, unsigned int stat\n \t\t/* Skip every 3th and 4th line, sample every other 2x2 block */\n \t\tySkipMask_ = 0x02;\n \t\txShift_ = 0;\n+\t\tsumShift_ = 0;\n \t\tprocessFrame_ = &SwStatsCpu::processBayerFrame2;\n \n \t\tswitch (bayerFormat.order) {\n","prefixes":["v5","2/3"]}