ipa: ipu3: Remove bespoke AGC functions from IPU3
Now that the IPU3's Agc is derived from MeanLuminanceAgc we can delete all the unecessary bespoke functions. Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com> Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com> Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
This commit is contained in:
Daniel Scally
Kieran Bingham
parent
87353f2bba
commit
9b9a7b3f32
2 changed files with 3 additions and 251 deletions
|
|
@ -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)
|
||||
{
|
||||
|
|
@ -207,123 +155,9 @@ 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 +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;
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue