@@ -125,8 +125,6 @@ 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 +136,6 @@ 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)
{
@@ -207,123 +169,9 @@ Histogram Agc::parseStatistics(const ipu3_uapi_stats_3a *stats,
return Histogram(Span<uint32_t>(hist));
}
-/**
- * \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 +186,9 @@ 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 +222,6 @@ 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;
@@ -38,29 +38,16 @@ public:
ControlList &metadata) override;
private:
- double measureBrightness(const ipu3_uapi_stats_3a *stats,
- const ipu3_uapi_grid_config &grid) const;
- utils::Duration filterExposure(utils::Duration currentExposure);
- void computeExposure(IPAContext &context, IPAFrameContext &frameContext,
- double yGain, double iqMeanGain);
- double estimateLuminance(IPAActiveState &activeState,
- const ipu3_uapi_grid_config &grid,
- const ipu3_uapi_stats_3a *stats,
- double gain);
double estimateLuminance(double gain) const override;
Histogram parseStatistics(const ipu3_uapi_stats_3a *stats,
const ipu3_uapi_grid_config &grid);
- uint64_t frameCount_;
-
utils::Duration minShutterSpeed_;
utils::Duration maxShutterSpeed_;
double minAnalogueGain_;
double maxAnalogueGain_;
- utils::Duration filteredExposure_;
-
uint32_t stride_;
double rGain_;
double gGain_;