[{"id":13742,"web_url":"https://patchwork.libcamera.org/comment/13742/","msgid":"","date":"2020-11-17T11:12:35","subject":"Re: [libcamera-devel] [PATCH 09/10] libcamera: src: ipa:\n\traspberrypi: agc: Improve gain update calculation for partly\n\tsaturated images","submitter":{"id":34,"url":"https://patchwork.libcamera.org/api/people/34/","name":"Naushir Patuck","email":"naush@raspberrypi.com"},"content":"Hi David,\n\n\nOn Mon, 16 Nov 2020 at 16:49, David Plowman \nwrote:\n\n> When parts of an image saturate then the image brightness no longer\n> increases linearly with increased exposure/gain. Having calculated a\n> linear gain value it's better then to try it, allowing for saturating\n> regions, and if necessary increase the gain some more. We repeat this\n> several times.\n>\n> Signed-off-by: David Plowman \n>\n\nReviewed-by: Naushir Patuck \n\n\n> ---\n> src/ipa/raspberrypi/controller/rpi/agc.cpp | 34 +++++++++++++++-------\n> 1 file changed, 24 insertions(+), 10 deletions(-)\n>\n> diff --git a/src/ipa/raspberrypi/controller/rpi/agc.cpp\n> b/src/ipa/raspberrypi/controller/rpi/agc.cpp\n> index 1037f968..93b46a28 100644\n> --- a/src/ipa/raspberrypi/controller/rpi/agc.cpp\n> +++ b/src/ipa/raspberrypi/controller/rpi/agc.cpp\n> @@ -422,17 +422,21 @@ void Agc::fetchAwbStatus(Metadata *image_metadata)\n> }\n>\n> static double compute_initial_Y(bcm2835_isp_stats *stats, AwbStatus const\n> &awb,\n> - double weights[])\n> + double weights[], double gain)\n> {\n> bcm2835_isp_stats_region *regions = stats->agc_stats;\n> // Note how the calculation below means that equal weights give you\n> // \"average\" metering (i.e. all pixels equally important).\n> double R_sum = 0, G_sum = 0, B_sum = 0, pixel_sum = 0;\n> for (int i = 0; i < AGC_STATS_SIZE; i++) {\n> - R_sum += regions[i].r_sum * weights[i];\n> - G_sum += regions[i].g_sum * weights[i];\n> - B_sum += regions[i].b_sum * weights[i];\n> - pixel_sum += regions[i].counted * weights[i];\n> + double counted = regions[i].counted;\n> + double r_sum = std::min(regions[i].r_sum * gain, ((1 <<\n> PIPELINE_BITS) - 1) * counted);\n> + double g_sum = std::min(regions[i].g_sum * gain, ((1 <<\n> PIPELINE_BITS) - 1) * counted);\n> + double b_sum = std::min(regions[i].b_sum * gain, ((1 <<\n> PIPELINE_BITS) - 1) * counted);\n> + R_sum += r_sum * weights[i];\n> + G_sum += g_sum * weights[i];\n> + B_sum += b_sum * weights[i];\n> + pixel_sum += counted * weights[i];\n> }\n> if (pixel_sum == 0.0) {\n> LOG(RPiAgc, Warning) << \"compute_initial_Y: pixel_sum is\n> zero\";\n> @@ -476,11 +480,21 @@ void Agc::computeGain(bcm2835_isp_stats *statistics,\n> Metadata *image_metadata,\n> target_Y =\n>\n> config_.Y_target.Eval(config_.Y_target.Domain().Clip(lux.lux));\n> target_Y = std::min(EV_GAIN_Y_TARGET_LIMIT, target_Y * ev_gain);\n> - double initial_Y = compute_initial_Y(statistics, awb_,\n> - metering_mode_->weights);\n> - gain = std::min(10.0, target_Y / (initial_Y + .001));\n> - LOG(RPiAgc, Debug) << \"Initially Y \" << initial_Y << \" target \" <<\n> target_Y\n> - << \" gives gain \" << gain;\n> +\n> + // Do this calculation a few times as brightness increase can be\n> + // non-linear when there are saturated regions.\n> + gain = 1.0;\n> + for (int i = 0; i < 8; i++) {\n> + double initial_Y = compute_initial_Y(statistics, awb_,\n> +\n> metering_mode_->weights, gain);\n> + double extra_gain = std::min(10.0, target_Y / (initial_Y +\n> .001));\n> + gain *= extra_gain;\n> + LOG(RPiAgc, Debug) << \"Initial Y \" << initial_Y << \"\n> target \" << target_Y\n> + << \" gives gain \" << gain;\n> + if (extra_gain < 1.01) // close enough\n> + break;\n> + }\n> +\n> for (auto &c : *constraint_mode_) {\n> double new_target_Y;\n> double new_gain =\n> --\n> 2.20.1\n>\n> _______________________________________________\n> libcamera-devel mailing list\n> libcamera-devel@lists.libcamera.org\n> https://lists.libcamera.org/listinfo/libcamera-devel\n>","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 B0E85BE081\n\tfor ;\n\tTue, 17 Nov 2020 11:12:55 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 437C363324;\n\tTue, 17 Nov 2020 12:12:55 +0100 (CET)","from mail-lj1-x229.google.com (mail-lj1-x229.google.com\n\t[IPv6:2a00:1450:4864:20::229])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 2DC7C63282\n\tfor ;\n\tTue, 17 Nov 2020 12:12:54 +0100 (CET)","by mail-lj1-x229.google.com with SMTP id 142so10162330ljj.10\n\tfor ;\n\tTue, 17 Nov 2020 03:12:54 -0800 (PST)"],"Authentication-Results":"lancelot.ideasonboard.com;\n\tdkim=fail reason=\"signature verification failed\" (2048-bit key;\n\tunprotected) header.d=raspberrypi.com header.i=@raspberrypi.com\n\theader.b=\"BJaTqqsE\"; 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\n\tTue, 17 Nov 2020 03:12:52 -0800 (PST)","MIME-Version":"1.0","References":"<20201116164918.2055-1-david.plowman@raspberrypi.com>\n\t<20201116164918.2055-10-david.plowman@raspberrypi.com>","In-Reply-To":"<20201116164918.2055-10-david.plowman@raspberrypi.com>","From":"Naushir Patuck ","Date":"Tue, 17 Nov 2020 11:12:35 +0000","Message-ID":"","To":"David Plowman ","Subject":"Re: [libcamera-devel] [PATCH 09/10] libcamera: src: ipa:\n\traspberrypi: agc: Improve gain update calculation for partly\n\tsaturated images","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","Cc":"libcamera-devel@lists.libcamera.org","Content-Type":"multipart/mixed;\n\tboundary=\"===============8101475379340968087==\"","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}}]