diff options
Diffstat (limited to 'src/ipa/ipu3/algorithms/agc.cpp')
| -rw-r--r-- | src/ipa/ipu3/algorithms/agc.cpp | 241 |
1 files changed, 3 insertions, 238 deletions
diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp index b1ba27fe..c9b5548c 100644 --- a/src/ipa/ipu3/algorithms/agc.cpp +++ b/src/ipa/ipu3/algorithms/agc.cpp @@ -56,20 +56,6 @@ static constexpr utils::Duration kMaxShutterSpeed = 60ms; /* Histogram constants */ static constexpr uint32_t knumHistogramBins = 256; -/* Target value to reach for the top 2% of the histogram */ -static constexpr double kEvGainTarget = 0.5; - -/* Number of frames to wait before calculating stats on minimum exposure */ -static constexpr uint32_t kNumStartupFrames = 10; - -/* - * Relative luminance 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 kRelativeLuminanceTarget = 0.16; - Agc::Agc() : minShutterSpeed_(0s), maxShutterSpeed_(0s) { @@ -125,8 +111,6 @@ int Agc::configure(IPAContext &context, activeState.agc.gain = minAnalogueGain_; activeState.agc.exposure = 10ms / configuration.sensor.lineDuration; - frameCount_ = 0; - context.activeState.agc.constraintMode = constraintModes().begin()->first; context.activeState.agc.exposureMode = exposureModeHelpers().begin()->first; @@ -138,42 +122,6 @@ int Agc::configure(IPAContext &context, return 0; } -/** - * \brief Estimate the mean value of the top 2% of the histogram - * \param[in] stats The statistics computed by the ImgU - * \param[in] grid The grid used to store the statistics in the IPU3 - * \return The mean value of the top 2% of the histogram - */ -double Agc::measureBrightness(const ipu3_uapi_stats_3a *stats, - const ipu3_uapi_grid_config &grid) const -{ - /* Initialise the histogram array */ - uint32_t hist[knumHistogramBins] = { 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<const ipu3_uapi_awb_set_item *>( - &stats->awb_raw_buffer.meta_data[cellPosition] - ); - - uint8_t gr = cell->Gr_avg; - uint8_t gb = cell->Gb_avg; - /* - * Store the average green value to estimate the - * brightness. Even the overexposed pixels are - * taken into account. - */ - hist[(gr + gb) / 2]++; - } - } - - /* Estimate the quantile mean of the top 2% of the histogram. */ - return Histogram(Span<uint32_t>(hist)).interQuantileMean(0.98, 1.0); -} - Histogram Agc::parseStatistics(const ipu3_uapi_stats_3a *stats, const ipu3_uapi_grid_config &grid) { @@ -208,122 +156,8 @@ Histogram Agc::parseStatistics(const ipu3_uapi_stats_3a *stats, } /** - * \brief Apply a filter on the exposure value to limit the speed of changes - * \param[in] exposureValue The target exposure from the AGC algorithm - * - * The speed of the filter is adaptive, and will produce the target quicker - * during startup, or when the target exposure is within 20% of the most recent - * filter output. - * - * \return The filtered exposure - */ -utils::Duration Agc::filterExposure(utils::Duration exposureValue) -{ - double speed = 0.2; - - /* Adapt instantly if we are in startup phase. */ - if (frameCount_ < kNumStartupFrames) - speed = 1.0; - - /* - * If we are close to the desired result, go faster to avoid making - * multiple micro-adjustments. - * \todo Make this customisable? - */ - if (filteredExposure_ < 1.2 * exposureValue && - filteredExposure_ > 0.8 * exposureValue) - speed = sqrt(speed); - - filteredExposure_ = speed * exposureValue + - filteredExposure_ * (1.0 - speed); - - LOG(IPU3Agc, Debug) << "After filtering, exposure " << filteredExposure_; - - return filteredExposure_; -} - -/** - * \brief Estimate the new exposure and gain values - * \param[inout] frameContext The shared IPA frame Context - * \param[in] yGain The gain calculated based on the relative luminance target - * \param[in] iqMeanGain The gain calculated based on the relative luminance target - */ -void Agc::computeExposure(IPAContext &context, IPAFrameContext &frameContext, - double yGain, double iqMeanGain) -{ - const IPASessionConfiguration &configuration = context.configuration; - /* Get the effective exposure and gain applied on the sensor. */ - uint32_t exposure = frameContext.sensor.exposure; - double analogueGain = frameContext.sensor.gain; - - /* Use the highest of the two gain estimates. */ - double evGain = std::max(yGain, iqMeanGain); - - /* Consider within 1% of the target as correctly exposed */ - if (utils::abs_diff(evGain, 1.0) < 0.01) - LOG(IPU3Agc, Debug) << "We are well exposed (evGain = " - << evGain << ")"; - - /* extracted from Rpi::Agc::computeTargetExposure */ - - /* Calculate the shutter time in seconds */ - utils::Duration currentShutter = exposure * configuration.sensor.lineDuration; - - /* - * Update the exposure value for the next computation using the values - * of exposure and gain really used by the sensor. - */ - utils::Duration effectiveExposureValue = currentShutter * analogueGain; - - LOG(IPU3Agc, Debug) << "Actual total exposure " << currentShutter * analogueGain - << " Shutter speed " << currentShutter - << " Gain " << analogueGain - << " Needed ev gain " << evGain; - - /* - * Calculate the current exposure value for the scene as the latest - * exposure value applied multiplied by the new estimated gain. - */ - utils::Duration exposureValue = effectiveExposureValue * evGain; - - /* Clamp the exposure value to the min and max authorized */ - utils::Duration maxTotalExposure = maxShutterSpeed_ * maxAnalogueGain_; - exposureValue = std::min(exposureValue, maxTotalExposure); - LOG(IPU3Agc, Debug) << "Target total exposure " << exposureValue - << ", maximum is " << maxTotalExposure; - - /* - * Filter the exposure. - * \todo estimate if we need to desaturate - */ - exposureValue = filterExposure(exposureValue); - - /* - * Divide the exposure value as new exposure and gain values. - * - * Push the shutter time up to the maximum first, and only then - * increase the gain. - */ - utils::Duration shutterTime = - std::clamp<utils::Duration>(exposureValue / minAnalogueGain_, - minShutterSpeed_, maxShutterSpeed_); - double stepGain = std::clamp(exposureValue / shutterTime, - minAnalogueGain_, maxAnalogueGain_); - LOG(IPU3Agc, Debug) << "Divided up shutter and gain are " - << shutterTime << " and " - << stepGain; -} - -/** * \brief Estimate the relative luminance of the frame with a given gain - * \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] gain The gain to apply to the frame - * \return The relative luminance - * - * This function estimates the average relative luminance of the frame that - * would be output by the sensor if an additional \a gain was applied. + * \param[in] gain The gain to apply in estimating luminance * * The estimation is based on the AWB statistics for the current frame. Red, * green and blue averages for all cells are first multiplied by the gain, and @@ -338,42 +172,9 @@ void Agc::computeExposure(IPAContext &context, IPAFrameContext &frameContext, * * More detailed information can be found in: * https://en.wikipedia.org/wiki/Relative_luminance + * + * \return The relative luminance of the frame */ -double Agc::estimateLuminance(IPAActiveState &activeState, - const ipu3_uapi_grid_config &grid, - const ipu3_uapi_stats_3a *stats, - double gain) -{ - double redSum = 0, greenSum = 0, blueSum = 0; - - /* Sum the per-channel averages, saturated to 255. */ - 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<const ipu3_uapi_awb_set_item *>( - &stats->awb_raw_buffer.meta_data[cellPosition] - ); - const uint8_t G_avg = (cell->Gr_avg + cell->Gb_avg) / 2; - - redSum += std::min(cell->R_avg * gain, 255.0); - greenSum += std::min(G_avg * gain, 255.0); - blueSum += std::min(cell->B_avg * gain, 255.0); - } - } - - /* - * Apply the AWB gains to approximate colours correctly, use the Rec. - * 601 formula to calculate the relative luminance, and normalize it. - */ - double ySum = redSum * activeState.awb.gains.red * 0.299 - + greenSum * activeState.awb.gains.green * 0.587 - + blueSum * activeState.awb.gains.blue * 0.114; - - return ySum / (grid.height * grid.width) / 255; -} - double Agc::estimateLuminance(double gain) const { double redSum = 0, greenSum = 0, blueSum = 0; @@ -407,42 +208,6 @@ void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame, const ipu3_uapi_stats_3a *stats, ControlList &metadata) { - /* - * Estimate the gain needed to have the proportion of pixels in a given - * desired range. iqMean is 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 iqMean = measureBrightness(stats, context.configuration.grid.bdsGrid); - double iqMeanGain = kEvGainTarget * knumHistogramBins / iqMean; - - /* - * Estimate the gain needed to achieve a relative luminance target. To - * account for non-linearity caused by saturation, the value needs to be - * estimated in an iterative process, as multiplying by a gain will not - * increase the relative luminance by the same factor if some image - * regions are saturated. - */ - double yGain = 1.0; - double yTarget = kRelativeLuminanceTarget; - - for (unsigned int i = 0; i < 8; i++) { - double yValue = estimateLuminance(context.activeState, - context.configuration.grid.bdsGrid, - stats, yGain); - double extraGain = std::min(10.0, yTarget / (yValue + .001)); - - yGain *= extraGain; - LOG(IPU3Agc, Debug) << "Y value: " << yValue - << ", Y target: " << yTarget - << ", gives gain " << yGain; - if (extraGain < 1.01) - break; - } - - computeExposure(context, frameContext, yGain, iqMeanGain); - frameCount_++; - Histogram hist = parseStatistics(stats, context.configuration.grid.bdsGrid); rGain_ = context.activeState.awb.gains.red; gGain_ = context.activeState.awb.gains.blue; |