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{
    "id": 18228,
    "url": "https://patchwork.libcamera.org/api/1.1/patches/18228/?format=api",
    "web_url": "https://patchwork.libcamera.org/patch/18228/",
    "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": "<20230131134646.9868-1-naush@raspberrypi.com>",
    "date": "2023-01-31T13:46:46",
    "name": "[libcamera-devel] ipa: raspberrypi: Normalise region sums to 16-bits",
    "commit_ref": null,
    "pull_url": null,
    "state": "superseded",
    "archived": false,
    "hash": "e44a725c42b77b4f0be995e3e38e0e99fafbfd21",
    "submitter": {
        "id": 34,
        "url": "https://patchwork.libcamera.org/api/1.1/people/34/?format=api",
        "name": "Naushir Patuck",
        "email": "naush@raspberrypi.com"
    },
    "delegate": null,
    "mbox": "https://patchwork.libcamera.org/patch/18228/mbox/",
    "series": [
        {
            "id": 3734,
            "url": "https://patchwork.libcamera.org/api/1.1/series/3734/?format=api",
            "web_url": "https://patchwork.libcamera.org/project/libcamera/list/?series=3734",
            "date": "2023-01-31T13:46:46",
            "name": "[libcamera-devel] ipa: raspberrypi: Normalise region sums to 16-bits",
            "version": 1,
            "mbox": "https://patchwork.libcamera.org/series/3734/mbox/"
        }
    ],
    "comments": "https://patchwork.libcamera.org/api/patches/18228/comments/",
    "check": "pending",
    "checks": "https://patchwork.libcamera.org/api/patches/18228/checks/",
    "tags": {},
    "headers": {
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        "To": "libcamera-devel@lists.libcamera.org",
        "Date": "Tue, 31 Jan 2023 13:46:46 +0000",
        "Message-Id": "<20230131134646.9868-1-naush@raspberrypi.com>",
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        "Content-Transfer-Encoding": "8bit",
        "Subject": "[libcamera-devel] [PATCH] ipa: raspberrypi: Normalise region sums\n\tto 16-bits",
        "X-BeenThere": "libcamera-devel@lists.libcamera.org",
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        "From": "Naushir Patuck via libcamera-devel\n\t<libcamera-devel@lists.libcamera.org>",
        "Reply-To": "Naushir Patuck <naush@raspberrypi.com>",
        "Errors-To": "libcamera-devel-bounces@lists.libcamera.org",
        "Sender": "\"libcamera-devel\" <libcamera-devel-bounces@lists.libcamera.org>"
    },
    "content": "The VC4 ISP uses a pipeline bit-depth of 13-bits. The AGC algorithm needs to\nknow this bit-depth when computing the Y value for the image.\n\nInstead of hardcoding the VC4 bit-depth in the AGC source code, normalise all\nregion sums to 16-bits when filling the Statistics structure. AWB and ALSC are\nagnostic about pipeline depth, so do not need changing.\n\nSigned-off-by: Naushir Patuck <naush@raspberrypi.com>\nReviewed-by: David Plowman <david.plowman@raspberrypi.com>\n---\n src/ipa/raspberrypi/controller/rpi/agc.cpp | 11 +++++------\n src/ipa/raspberrypi/raspberrypi.cpp        | 18 ++++++++++++------\n src/ipa/raspberrypi/statistics.h           |  6 ++++++\n 3 files changed, 23 insertions(+), 12 deletions(-)",
    "diff": "diff --git a/src/ipa/raspberrypi/controller/rpi/agc.cpp b/src/ipa/raspberrypi/controller/rpi/agc.cpp\nindex 868c30f03d66..ea0c82b5c4c8 100644\n--- a/src/ipa/raspberrypi/controller/rpi/agc.cpp\n+++ b/src/ipa/raspberrypi/controller/rpi/agc.cpp\n@@ -28,8 +28,6 @@ LOG_DEFINE_CATEGORY(RPiAgc)\n \n #define NAME \"rpi.agc\"\n \n-static constexpr unsigned int PipelineBits = 13; /* seems to be a 13-bit pipeline */\n-\n int AgcMeteringMode::read(const libcamera::YamlObject &params)\n {\n \tconst YamlObject &yamlWeights = params[\"weights\"];\n@@ -586,6 +584,7 @@ void Agc::fetchAwbStatus(Metadata *imageMetadata)\n static double computeInitialY(StatisticsPtr &stats, AwbStatus const &awb,\n \t\t\t      double weights[], double gain)\n {\n+\tconstexpr unsigned int maxVal = 1 << Statistics::NormalisationFactorPow2;\n \t/*\n \t * Note how the calculation below means that equal weights give you\n \t * \"average\" metering (i.e. all pixels equally important).\n@@ -593,9 +592,9 @@ static double computeInitialY(StatisticsPtr &stats, AwbStatus const &awb,\n \tdouble rSum = 0, gSum = 0, bSum = 0, pixelSum = 0;\n \tfor (unsigned int i = 0; i < stats->agcRegions.numRegions(); i++) {\n \t\tauto &region = stats->agcRegions.get(i);\n-\t\tdouble rAcc = std::min<double>(region.val.rSum * gain, ((1 << PipelineBits) - 1) * region.counted);\n-\t\tdouble gAcc = std::min<double>(region.val.gSum * gain, ((1 << PipelineBits) - 1) * region.counted);\n-\t\tdouble bAcc = std::min<double>(region.val.bSum * gain, ((1 << PipelineBits) - 1) * region.counted);\n+\t\tdouble rAcc = std::min<double>(region.val.rSum * gain, (maxVal - 1) * region.counted);\n+\t\tdouble gAcc = std::min<double>(region.val.gSum * gain, (maxVal - 1) * region.counted);\n+\t\tdouble bAcc = std::min<double>(region.val.bSum * gain, (maxVal - 1) * region.counted);\n \t\trSum += rAcc * weights[i];\n \t\tgSum += gAcc * weights[i];\n \t\tbSum += bAcc * weights[i];\n@@ -608,7 +607,7 @@ static double computeInitialY(StatisticsPtr &stats, AwbStatus const &awb,\n \tdouble ySum = rSum * awb.gainR * .299 +\n \t\t      gSum * awb.gainG * .587 +\n \t\t      bSum * awb.gainB * .114;\n-\treturn ySum / pixelSum / (1 << PipelineBits);\n+\treturn ySum / pixelSum / maxVal;\n }\n \n /*\ndiff --git a/src/ipa/raspberrypi/raspberrypi.cpp b/src/ipa/raspberrypi/raspberrypi.cpp\nindex cff079bbafb3..1cf7649c3303 100644\n--- a/src/ipa/raspberrypi/raspberrypi.cpp\n+++ b/src/ipa/raspberrypi/raspberrypi.cpp\n@@ -1154,11 +1154,17 @@ RPiController::StatisticsPtr IPARPi::fillStatistics(bcm2835_isp_stats *stats) co\n \t/* RGB histograms are not used, so do not populate them. */\n \tstatistics->yHist = std::move(RPiController::Histogram(stats->hist[0].g_hist, NUM_HISTOGRAM_BINS));\n \n+\t/*\n+\t * All region sums are based on a 13-bit pipeline bit-depth. Normalise\n+\t * this to 16-bits for the AGC/AWB/ALSC algorithms.\n+\t */\n+\tconstexpr unsigned int scale = Statistics::NormalisationFactorPow2 - 13;\n+\n \tstatistics->awbRegions.init({ DEFAULT_AWB_REGIONS_X, DEFAULT_AWB_REGIONS_Y });\n \tfor (i = 0; i < statistics->awbRegions.numRegions(); i++)\n-\t\tstatistics->awbRegions.set(i, { { stats->awb_stats[i].r_sum,\n-\t\t\t\t\t\t  stats->awb_stats[i].g_sum,\n-\t\t\t\t\t\t  stats->awb_stats[i].b_sum },\n+\t\tstatistics->awbRegions.set(i, { { stats->awb_stats[i].r_sum << scale,\n+\t\t\t\t\t\t  stats->awb_stats[i].g_sum << scale,\n+\t\t\t\t\t\t  stats->awb_stats[i].b_sum << scale },\n \t\t\t\t\t\tstats->awb_stats[i].counted,\n \t\t\t\t\t\tstats->awb_stats[i].notcounted });\n \n@@ -1168,9 +1174,9 @@ RPiController::StatisticsPtr IPARPi::fillStatistics(bcm2835_isp_stats *stats) co\n \t */\n \tstatistics->agcRegions.init(15);\n \tfor (i = 0; i < statistics->agcRegions.numRegions(); i++)\n-\t\tstatistics->agcRegions.set(i, { { stats->agc_stats[i].r_sum,\n-\t\t\t\t\t\t  stats->agc_stats[i].g_sum,\n-\t\t\t\t\t\t  stats->agc_stats[i].b_sum },\n+\t\tstatistics->agcRegions.set(i, { { stats->agc_stats[i].r_sum << scale,\n+\t\t\t\t\t\t  stats->agc_stats[i].g_sum << scale,\n+\t\t\t\t\t\t  stats->agc_stats[i].b_sum << scale },\n \t\t\t\t\t\tstats->agc_stats[i].counted,\n \t\t\t\t\t\tstats->awb_stats[i].notcounted });\n \ndiff --git a/src/ipa/raspberrypi/statistics.h b/src/ipa/raspberrypi/statistics.h\nindex affb7272c963..22a72c94a90d 100644\n--- a/src/ipa/raspberrypi/statistics.h\n+++ b/src/ipa/raspberrypi/statistics.h\n@@ -30,6 +30,12 @@ using RgbyRegions = RegionStats<RgbySums>;\n using FocusRegions = RegionStats<uint64_t>;\n \n struct Statistics {\n+\t/*\n+\t * All histogram and region based statistics are scaled to a maximum\n+\t * value given by (1 << NormalisationFactorPow2) - 1.\n+\t */\n+\tstatic constexpr unsigned int NormalisationFactorPow2 = 16;\n+\n \t/*\n \t * Positioning of the AGC statistics gathering in the pipeline:\n \t * Pre-WB correction or post-WB correction.\n",
    "prefixes": [
        "libcamera-devel"
    ]
}