[{"id":34202,"web_url":"https://patchwork.libcamera.org/comment/34202/","msgid":"<174705354159.521251.10316650001635354290@pyrite.rasen.tech>","date":"2025-05-12T12:39:01","subject":"Re: [PATCH 4/8] ipa: rkisp1: Add correction for exposure\n\tquantization","submitter":{"id":17,"url":"https://patchwork.libcamera.org/api/people/17/","name":"Paul Elder","email":"paul.elder@ideasonboard.com"},"content":"Hi Stefan,\n\nThanks for the patch.\n\nQuoting Stefan Klug (2025-04-11 15:04:11)\n> When WDR regulation is active, it can happen that exposure times get set\n> to very low values (Sometimes 2-3 lines). This intentionally introduced\n> underexposure is corrected by the GWDR module. As exposure time is\n> quantized by lines, the smalles possible change in exposure time now\n\ns/smalles/smallest/\n\n> results in a quite visible change in perceived brightness.\n\nI see, at very low exposure then gainLostInExposureQuantization becomes quite\nsignificant. \n\n> Mitigate that by applying a small global gain to account for the error\n> introduced by the exposure quantization.\n\nAnd we want to set it globally in awb for lower latency as opposed to in the\nsensor, ok. I suppose this is how we'd do digital gain eventually too maybe.\n\n> ToDo: This needs perfect frame synchronous control of the sensor to work\n> properly which is not guaranteed in all cases. It still improves the\n> behavior with the current regulation.\n\nWould this be good to capture as a comment? Or maybe it's fine because it's a\ngeneral pfc problem. Either way is fine.\n\n> \n> Signed-off-by: Stefan Klug \n> ---\n> src/ipa/rkisp1/algorithms/agc.cpp | 2 ++\n> src/ipa/rkisp1/algorithms/awb.cpp | 12 ++++++++----\n> src/ipa/rkisp1/ipa_context.h | 2 ++\n> 3 files changed, 12 insertions(+), 4 deletions(-)\n> \n> diff --git a/src/ipa/rkisp1/algorithms/agc.cpp b/src/ipa/rkisp1/algorithms/agc.cpp\n> index 8e77455e7afd..0e4fd3663167 100644\n> --- a/src/ipa/rkisp1/algorithms/agc.cpp\n> +++ b/src/ipa/rkisp1/algorithms/agc.cpp\n> @@ -583,6 +583,8 @@ void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame,\n> activeState.agc.automatic.exposure = newExposureTime / lineDuration;\n> activeState.agc.automatic.gain = aGain;\n> \n> + activeState.agc.automatic.gainLostInExposureQuantization =\n\nDoesn't this need to be initialized to 1.0 in configure() ?\n\n\nPaul\n\n> + newExposureTime / (activeState.agc.automatic.exposure * lineDuration);\n> /*\n> * Expand the target frame duration so that we do not run faster than\n> * the minimum frame duration when we have short exposures.\n> diff --git a/src/ipa/rkisp1/algorithms/awb.cpp b/src/ipa/rkisp1/algorithms/awb.cpp\n> index 84aa1d29419d..cc78136a22c8 100644\n> --- a/src/ipa/rkisp1/algorithms/awb.cpp\n> +++ b/src/ipa/rkisp1/algorithms/awb.cpp\n> @@ -170,6 +170,7 @@ void Awb::queueRequest(IPAContext &context,\n> awbAlgo_->handleControls(controls);\n> \n> frameContext.awb.autoEnabled = awb.autoEnabled;\n> + frameContext.awb.additionalGain = 1.0;\n> \n> if (awb.autoEnabled)\n> return;\n> @@ -218,15 +219,18 @@ void Awb::prepare(IPAContext &context, const uint32_t frame,\n> auto &awb = context.activeState.awb;\n> frameContext.awb.gains = awb.automatic.gains;\n> frameContext.awb.temperatureK = awb.automatic.temperatureK;\n> + frameContext.awb.additionalGain =\n> + context.activeState.agc.automatic.gainLostInExposureQuantization;\n> }\n> \n> + auto gains = frameContext.awb.gains * frameContext.awb.additionalGain;\n> auto gainConfig = params->block();\n> gainConfig.setEnabled(true);\n> \n> - gainConfig->gain_green_b = std::clamp(256 * frameContext.awb.gains.g(), 0, 0x3ff);\n> - gainConfig->gain_blue = std::clamp(256 * frameContext.awb.gains.b(), 0, 0x3ff);\n> - gainConfig->gain_red = std::clamp(256 * frameContext.awb.gains.r(), 0, 0x3ff);\n> - gainConfig->gain_green_r = std::clamp(256 * frameContext.awb.gains.g(), 0, 0x3ff);\n> + gainConfig->gain_green_b = std::clamp(256 * gains.g(), 0, 0x3ff);\n> + gainConfig->gain_blue = std::clamp(256 * gains.b(), 0, 0x3ff);\n> + gainConfig->gain_red = std::clamp(256 * gains.r(), 0, 0x3ff);\n> + gainConfig->gain_green_r = std::clamp(256 * gains.g(), 0, 0x3ff);\n> \n> /* If we have already set the AWB measurement parameters, return. */\n> if (frame > 0)\n> diff --git a/src/ipa/rkisp1/ipa_context.h b/src/ipa/rkisp1/ipa_context.h\n> index 7ccc7b501aff..182203880ac9 100644\n> --- a/src/ipa/rkisp1/ipa_context.h\n> +++ b/src/ipa/rkisp1/ipa_context.h\n> @@ -76,6 +76,7 @@ struct IPAActiveState {\n> } manual;\n> struct {\n> uint32_t exposure;\n> + double gainLostInExposureQuantization;\n> double gain;\n> } automatic;\n> \n> @@ -149,6 +150,7 @@ struct IPAFrameContext : public FrameContext {\n> RGB gains;\n> bool autoEnabled;\n> unsigned int temperatureK;\n> + double additionalGain;\n> } awb;\n> \n> struct {\n> -- \n> 2.43.0\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 88E0FC3200\n\tfor ;\n\tMon, 12 May 2025 12:39:07 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id E45FB68B40;\n\tMon, 12 May 2025 14:39:05 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 58055614E3\n\tfor ;\n\tMon, 12 May 2025 14:39:04 +0200 (CEST)","from pyrite.rasen.tech (unknown\n\t[IPv6:2001:861:3a80:3300:4f2f:8c2c:b3ef:17d4])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 3F77B4C9;\n\tMon, 12 May 2025 14:38:49 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; 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