From patchwork Thu Nov 11 14:09:21 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Jean-Michel Hautbois X-Patchwork-Id: 14578 Return-Path: X-Original-To: parsemail@patchwork.libcamera.org Delivered-To: parsemail@patchwork.libcamera.org Received: from lancelot.ideasonboard.com (lancelot.ideasonboard.com [92.243.16.209]) by patchwork.libcamera.org (Postfix) with ESMTPS id A5345C3250 for ; Thu, 11 Nov 2021 14:09:42 +0000 (UTC) Received: from lancelot.ideasonboard.com (localhost [IPv6:::1]) by lancelot.ideasonboard.com (Postfix) with ESMTP id 0F7ED60441; Thu, 11 Nov 2021 15:09:42 +0100 (CET) Authentication-Results: lancelot.ideasonboard.com; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="BYm6HyZP"; dkim-atps=neutral Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by lancelot.ideasonboard.com (Postfix) with ESMTPS id 8D6CC6036C for ; Thu, 11 Nov 2021 15:09:32 +0100 (CET) Received: from tatooine.ideasonboard.com (unknown [IPv6:2a01:e0a:169:7140:e627:8337:a781:d98]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 463C61543; Thu, 11 Nov 2021 15:09:32 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1636639772; bh=BeJz93F6GMcTUgsLx2/ns6lOLKAugtTQPDs0TL8H4uc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BYm6HyZPjf0JqgyAyG4KV1Dw8ZUE3NsRj/X5MM6xPyJubXY62/uVZrDuRPfjQYTmA 0PyAWnYI/Wk0AhJIuXunEuFwLshfU0N3PJ/S+tFQRY8O6Fj6i14K3l8+wKzBFyw18G 0qGz6L+6KIGSOo1fdDhh7XSHKL+l9a4W0NRXMG4U= From: Jean-Michel Hautbois To: libcamera-devel@lists.libcamera.org Date: Thu, 11 Nov 2021 15:09:21 +0100 Message-Id: <20211111140928.136111-8-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 Subject: [libcamera-devel] [PATCH v4 07/14] ipa: ipu3: agc: Improve gain calculation X-BeenThere: libcamera-devel@lists.libcamera.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: libcamera-devel-bounces@lists.libcamera.org Sender: "libcamera-devel" When an image is partially saturated, its brightness is not increasing linearly when the shutter time or gain increases. It is a big issue with a backlight as the algorithm is fading to darkness right now. Introduce a function to estimate the brightness of the frame, based on the current exposure/gain and loop on it several times to estimate it again and approach the non linear function. Inspired-by: 7de5506c30b3 ("libcamera: src: ipa: raspberrypi: agc: Improve gain update calculation for partly saturated images") Signed-off-by: Jean-Michel Hautbois Reviewed-by: Kieran Bingham Reviewed-by: Paul Elder --- src/ipa/ipu3/algorithms/agc.cpp | 104 +++++++++++++++++++++++++++++++- src/ipa/ipu3/algorithms/agc.h | 6 +- 2 files changed, 106 insertions(+), 4 deletions(-) diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp index 61ca8b3f..a34f070e 100644 --- a/src/ipa/ipu3/algorithms/agc.cpp +++ b/src/ipa/ipu3/algorithms/agc.cpp @@ -67,6 +67,17 @@ static constexpr uint32_t kMinCellsPerZoneRatio = 255 * 20 / 100; /* Number of frames to wait before calculating stats on minimum exposure */ static constexpr uint32_t kNumStartupFrames = 10; +/* Maximum luminance used for brightness normalization */ +static constexpr uint32_t kMaxLuminance = 255; + +/* + * Normalized luma value target. + * + * It's a number that's chosen so that, when the camera points at a grey + * target, the resulting image brightness is considered right. + */ +static constexpr double kNormalizedLumaTarget = 0.16; + Agc::Agc() : frameCount_(0), iqMean_(0.0), lineDuration_(0s), minExposureLines_(0), maxExposureLines_(0), filteredExposure_(0s), currentExposure_(0s), @@ -185,14 +196,20 @@ void Agc::filterExposure() /** * \brief Estimate the new exposure and gain values * \param[inout] frameContext The shared IPA frame Context + * \param[in] currentYGain The gain calculated on the current brightness level */ -void Agc::computeExposure(IPAFrameContext &frameContext) +void Agc::computeExposure(IPAFrameContext &frameContext, double currentYGain) { /* Get the effective exposure and gain applied on the sensor. */ uint32_t exposure = frameContext.sensor.exposure; double analogueGain = frameContext.sensor.gain; - /* Estimate the gain needed to have the proportion wanted */ + /* + * Estimate the gain needed to have the proportion of pixels in a given + * range wanted. iqMean_ returns the mean value of the top 2% of the + * cumulative histogram, and we want it to be as close as possible to a + * configured target. + */ double evGain = kEvGainTarget * knumHistogramBins / iqMean_; if (std::abs(evGain - 1.0) < 0.01) { @@ -202,6 +219,7 @@ void Agc::computeExposure(IPAFrameContext &frameContext) } /* extracted from Rpi::Agc::computeTargetExposure */ + /* Calculate the shutter time in seconds */ utils::Duration currentShutter = exposure * lineDuration_; LOG(IPU3Agc, Debug) << "Actual total exposure " << currentShutter * analogueGain @@ -209,6 +227,14 @@ void Agc::computeExposure(IPAFrameContext &frameContext) << " Gain " << analogueGain << " Needed ev gain " << evGain; + if (evGain < currentYGain) + evGain = currentYGain; + + /* Consider within 1% of the target as correctly exposed */ + if (std::abs(evGain - 1.0) < 0.01) + LOG(IPU3Agc, Debug) << "We are well exposed (iqMean = " + << iqMean_ << ")"; + /* * Calculate the current exposure value for the scene as the latest * exposure value applied multiplied by the new estimated gain. @@ -257,6 +283,56 @@ void Agc::computeExposure(IPAFrameContext &frameContext) prevExposureValue_ = shutterTime * analogueGain; } +/** + * \brief Estimate the average brightness of the frame + * \param[in] frameContext The shared IPA frame context + * \param[in] grid The grid used to store the statistics in the IPU3 + * \param[in] stats The IPU3 statistics and ISP results + * \param[in] currentYGain The gain calculated on the current brightness level + * \return The normalized luma + * + * Luma is the weighted sum of gamma-compressed R′G′B′ components of a color + * video. The luma values are normalized as 0.0 to 1.0, with 1.0 being a + * theoretical perfect reflector of 100% reference white. We use the Rec. 601 + * luma here. + * + * More detailed information can be found in: + * https://en.wikipedia.org/wiki/Luma_(video) + */ +double Agc::computeInitialY(IPAFrameContext &frameContext, + const ipu3_uapi_grid_config &grid, + const ipu3_uapi_stats_3a *stats, + double currentYGain) +{ + double redSum = 0, greenSum = 0, blueSum = 0; + + for (unsigned int cellY = 0; cellY < grid.height; cellY++) { + for (unsigned int cellX = 0; cellX < grid.width; cellX++) { + uint32_t cellPosition = cellY * stride_ + cellX; + + const ipu3_uapi_awb_set_item *cell = + reinterpret_cast( + &stats->awb_raw_buffer.meta_data[cellPosition] + ); + + redSum += cell->R_avg * currentYGain; + greenSum += (cell->Gr_avg + cell->Gb_avg) / 2 * currentYGain; + blueSum += cell->B_avg * currentYGain; + } + } + + /* + * Estimate the sum of the brightness values, weighted with the gains + * applied on the channels in AWB as the Rec. 601 luma. + */ + double Y_sum = redSum * frameContext.awb.gains.red * .299 + + greenSum * frameContext.awb.gains.green * .587 + + blueSum * frameContext.awb.gains.blue * .114; + + /* Return the normalized relative luminance. */ + return Y_sum / (grid.height * grid.width) / kMaxLuminance; +} + /** * \brief Process IPU3 statistics, and run AGC operations * \param[in] context The shared IPA context @@ -268,7 +344,29 @@ void Agc::computeExposure(IPAFrameContext &frameContext) void Agc::process(IPAContext &context, const ipu3_uapi_stats_3a *stats) { measureBrightness(stats, context.configuration.grid.bdsGrid); - computeExposure(context.frameContext); + + double currentYGain = 1.0; + double targetY = kNormalizedLumaTarget; + + /* + * Do this calculation a few times as brightness increase can be + * non-linear when there are saturated regions. + */ + for (int i = 0; i < 8; i++) { + double initialY = computeInitialY(context.frameContext, + context.configuration.grid.bdsGrid, + stats, currentYGain); + double extra_gain = std::min(10.0, targetY / (initialY + .001)); + + currentYGain *= extra_gain; + LOG(IPU3Agc, Debug) << "Initial Y " << initialY + << " target " << targetY + << " gives gain " << currentYGain; + if (extra_gain < 1.01) + break; + } + + computeExposure(context.frameContext, currentYGain); frameCount_++; } diff --git a/src/ipa/ipu3/algorithms/agc.h b/src/ipa/ipu3/algorithms/agc.h index f0db25ee..79736283 100644 --- a/src/ipa/ipu3/algorithms/agc.h +++ b/src/ipa/ipu3/algorithms/agc.h @@ -34,7 +34,11 @@ private: void measureBrightness(const ipu3_uapi_stats_3a *stats, const ipu3_uapi_grid_config &grid); void filterExposure(); - void computeExposure(IPAFrameContext &frameContext); + void computeExposure(IPAFrameContext &frameContext, double currentYGain); + double computeInitialY(IPAFrameContext &frameContext, + const ipu3_uapi_grid_config &grid, + const ipu3_uapi_stats_3a *stats, + double currentYGain); uint64_t frameCount_; uint64_t lastFrame_;