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{ "id": 26258, "url": "https://patchwork.libcamera.org/api/1.1/patches/26258/?format=api", "web_url": "https://patchwork.libcamera.org/patch/26258/", "project": { "id": 1, "url": "https://patchwork.libcamera.org/api/1.1/projects/1/?format=api", "name": "libcamera", "link_name": "libcamera", "list_id": "libcamera_core", "list_email": "libcamera-devel@lists.libcamera.org", "web_url": "", "scm_url": "", "webscm_url": "" }, "msgid": "<20260304232533.56D641EA006B@mailuser.phl.internal>", "date": "2026-03-04T23:13:46", "name": "[v2,2/4] libcamera: software_isp: Normalize statistics sums to 8-bit", "commit_ref": null, "pull_url": null, "state": "superseded", "archived": false, "hash": "f15aa23cf03fd5bcd192016a8f94eeb3e6edf6df", "submitter": { "id": 261, "url": "https://patchwork.libcamera.org/api/1.1/people/261/?format=api", "name": "Javier Tia", "email": "floss@jetm.me" }, "delegate": null, "mbox": "https://patchwork.libcamera.org/patch/26258/mbox/", "series": [ { "id": 5821, "url": "https://patchwork.libcamera.org/api/1.1/series/5821/?format=api", "web_url": "https://patchwork.libcamera.org/project/libcamera/list/?series=5821", "date": "2026-03-04T23:13:46", "name": null, "version": 2, "mbox": "https://patchwork.libcamera.org/series/5821/mbox/" } ], "comments": "https://patchwork.libcamera.org/api/patches/26258/comments/", "check": "pending", "checks": "https://patchwork.libcamera.org/api/patches/26258/checks/", "tags": {}, "headers": { "Return-Path": "<libcamera-devel-bounces@lists.libcamera.org>", "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 63803BE086\n\tfor <parsemail@patchwork.libcamera.org>;\n\tWed, 4 Mar 2026 23:25:36 +0000 (UTC)", "from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 297A8625E1;\n\tThu, 5 Mar 2026 00:25:36 +0100 (CET)", "from fout-b7-smtp.messagingengine.com\n\t(fout-b7-smtp.messagingengine.com [202.12.124.150])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 7396B623B5\n\tfor <libcamera-devel@lists.libcamera.org>;\n\tThu, 5 Mar 2026 00:25:34 +0100 (CET)", "from phl-compute-02.internal (phl-compute-02.internal\n\t[10.202.2.42])\n\tby mailfout.stl.internal (Postfix) with ESMTP id 9E3361D0020E\n\tfor <libcamera-devel@lists.libcamera.org>;\n\tWed, 4 Mar 2026 18:25:33 -0500 (EST)", "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 <floss@jetm.me>", "To": "libcamera-devel@lists.libcamera.org", "Date": "Wed, 04 Mar 2026 17:13:46 -0600", "Subject": "[PATCH v2 2/4] libcamera: software_isp: Normalize statistics sums to\n\t8-bit", "In-Reply-To": "20260225221859.600869-1-floss@jetm.me", "References": "20260225221859.600869-1-floss@jetm.me", "Message-Id": "<20260304232533.56D641EA006B@mailuser.phl.internal>", "X-BeenThere": "libcamera-devel@lists.libcamera.org", "X-Mailman-Version": "2.1.29", "Precedence": "list", "List-Id": "<libcamera-devel.lists.libcamera.org>", "List-Unsubscribe": "<https://lists.libcamera.org/options/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=unsubscribe>", "List-Archive": "<https://lists.libcamera.org/pipermail/libcamera-devel/>", "List-Post": "<mailto:libcamera-devel@lists.libcamera.org>", "List-Help": "<mailto:libcamera-devel-request@lists.libcamera.org?subject=help>", "List-Subscribe": "<https://lists.libcamera.org/listinfo/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=subscribe>", "Errors-To": "libcamera-devel-bounces@lists.libcamera.org", "Sender": "\"libcamera-devel\" <libcamera-devel-bounces@lists.libcamera.org>" }, "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 <floss@jetm.me>\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 64b3e23f..37bfde53 100644\n--- a/include/libcamera/internal/software_isp/swstats_cpu.h\n+++ b/include/libcamera/internal/software_isp/swstats_cpu.h\n@@ -115,6 +115,7 @@ private:\n \n \tunsigned int xShift_;\n \tunsigned int stride_;\n+\tunsigned int sumShift_;\n \n \tSharedMemObject<SwIspStats> sharedStats_;\n \tSwIspStats stats_;\ndiff --git a/src/libcamera/software_isp/swstats_cpu.cpp b/src/libcamera/software_isp/swstats_cpu.cpp\nindex 5c3011a7..bf5e1960 100644\n--- a/src/libcamera/software_isp/swstats_cpu.cpp\n+++ b/src/libcamera/software_isp/swstats_cpu.cpp\n@@ -346,6 +346,11 @@ void SwStatsCpu::startFrame(uint32_t frame)\n void SwStatsCpu::finishFrame(uint32_t frame, uint32_t bufferId)\n {\n \tstats_.valid = frame % kStatPerNumFrames == 0;\n+\tif (stats_.valid && sumShift_) {\n+\t\tstats_.sum_.r() >>= sumShift_;\n+\t\tstats_.sum_.g() >>= sumShift_;\n+\t\tstats_.sum_.b() >>= sumShift_;\n+\t}\n \t*sharedStats_ = stats_;\n \tstatsReady.emit(frame, bufferId);\n }\n@@ -405,12 +410,15 @@ int SwStatsCpu::configure(const StreamConfiguration &inputCfg)\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@@ -422,6 +430,7 @@ int SwStatsCpu::configure(const StreamConfiguration &inputCfg)\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": [ "v2", "2/4" ] }