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{
    "id": 14574,
    "url": "https://patchwork.libcamera.org/api/patches/14574/?format=api",
    "web_url": "https://patchwork.libcamera.org/patch/14574/",
    "project": {
        "id": 1,
        "url": "https://patchwork.libcamera.org/api/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": "<20211111140928.136111-5-jeanmichel.hautbois@ideasonboard.com>",
    "date": "2021-11-11T14:09:18",
    "name": "[libcamera-devel,v4,04/14] ipa: ipu3: agc: Limit the number of saturated cells",
    "commit_ref": null,
    "pull_url": null,
    "state": "accepted",
    "archived": false,
    "hash": "9ae9e8c44f776fa9318d1050fc0aebc2b4b5bccd",
    "submitter": {
        "id": 75,
        "url": "https://patchwork.libcamera.org/api/people/75/?format=api",
        "name": "Jean-Michel Hautbois",
        "email": "jeanmichel.hautbois@ideasonboard.com"
    },
    "delegate": null,
    "mbox": "https://patchwork.libcamera.org/patch/14574/mbox/",
    "series": [
        {
            "id": 2714,
            "url": "https://patchwork.libcamera.org/api/series/2714/?format=api",
            "web_url": "https://patchwork.libcamera.org/project/libcamera/list/?series=2714",
            "date": "2021-11-11T14:09:14",
            "name": "IPA: IPU3: Introduce per-frame controls",
            "version": 4,
            "mbox": "https://patchwork.libcamera.org/series/2714/mbox/"
        }
    ],
    "comments": "https://patchwork.libcamera.org/api/patches/14574/comments/",
    "check": "pending",
    "checks": "https://patchwork.libcamera.org/api/patches/14574/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 5DF8AC324E\n\tfor <parsemail@patchwork.libcamera.org>;\n\tThu, 11 Nov 2021 14:09:40 +0000 (UTC)",
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        ],
        "Authentication-Results": "lancelot.ideasonboard.com;\n\tdkim=fail reason=\"signature verification failed\" (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"CJrO0Uiq\"; dkim-atps=neutral",
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        "From": "Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>",
        "To": "libcamera-devel@lists.libcamera.org",
        "Date": "Thu, 11 Nov 2021 15:09:18 +0100",
        "Message-Id": "<20211111140928.136111-5-jeanmichel.hautbois@ideasonboard.com>",
        "X-Mailer": "git-send-email 2.32.0",
        "In-Reply-To": "<20211111140928.136111-1-jeanmichel.hautbois@ideasonboard.com>",
        "References": "<20211111140928.136111-1-jeanmichel.hautbois@ideasonboard.com>",
        "MIME-Version": "1.0",
        "Content-Transfer-Encoding": "8bit",
        "Subject": "[libcamera-devel] [PATCH v4 04/14] ipa: ipu3: agc: Limit the number\n\tof saturated cells",
        "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": "When the histogram is calculated, we check if a cell is saturated or not\nbefore cumulating its green value. This is wrong, and it can lead to an\nempty histogram in case of a fully saturated frame.\n\nUse a constant to limit the amount of pixels within a cell before\nconsidering it saturated. If at the end of the loop we still have an\nempty histogram, then make it a fully saturated one.\n\nBug: https://bugs.libcamera.org/show_bug.cgi?id=84\nSigned-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>\nReviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>\n---\n src/ipa/ipu3/algorithms/agc.cpp | 16 ++++++++++++++--\n 1 file changed, 14 insertions(+), 2 deletions(-)",
    "diff": "diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp\nindex 5723f6f3..83aa3676 100644\n--- a/src/ipa/ipu3/algorithms/agc.cpp\n+++ b/src/ipa/ipu3/algorithms/agc.cpp\n@@ -63,6 +63,12 @@ static constexpr uint32_t knumHistogramBins = 256;\n /* Target value to reach for the top 2% of the histogram */\n static constexpr double kEvGainTarget = 0.5;\n \n+/*\n+ * Maximum ratio of saturated pixels in a cell for the cell to be considered\n+ * non-saturated and counted by the AGC algorithm.\n+ */\n+static constexpr uint32_t kMinCellsPerZoneRatio = 255 * 20 / 100;\n+\n Agc::Agc()\n \t: frameCount_(0), lastFrame_(0), iqMean_(0.0), lineDuration_(0s),\n \t  minExposureLines_(0), maxExposureLines_(0), filteredExposure_(0s),\n@@ -124,7 +130,7 @@ void Agc::measureBrightness(const ipu3_uapi_stats_3a *stats,\n \t\t\t\t\t&stats->awb_raw_buffer.meta_data[cellPosition]\n \t\t\t\t);\n \n-\t\t\tif (cell->sat_ratio == 0) {\n+\t\t\tif (cell->sat_ratio <= kMinCellsPerZoneRatio) {\n \t\t\t\tuint8_t gr = cell->Gr_avg;\n \t\t\t\tuint8_t gb = cell->Gb_avg;\n \t\t\t\t/*\n@@ -137,8 +143,14 @@ void Agc::measureBrightness(const ipu3_uapi_stats_3a *stats,\n \t\t}\n \t}\n \n+\tHistogram cumulativeHist = Histogram(Span<uint32_t>(hist));\n \t/* Estimate the quantile mean of the top 2% of the histogram */\n-\tiqMean_ = Histogram(Span<uint32_t>(hist)).interQuantileMean(0.98, 1.0);\n+\tif (cumulativeHist.total() == 0) {\n+\t\t/* Force the value as histogram is empty */\n+\t\tiqMean_ = knumHistogramBins - 0.5;\n+\t} else {\n+\t\tiqMean_ = cumulativeHist.interQuantileMean(0.98, 1.0);\n+\t}\n }\n \n /**\n",
    "prefixes": [
        "libcamera-devel",
        "v4",
        "04/14"
    ]
}