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ipa: ipu3: agc: Limit the number of saturated cells

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When the histogram is calculated, we check if a cell is saturated or not
before cumulating its green value. This is wrong, and it can lead to an
empty histogram in case of a fully saturated frame.

Use a constant to limit the amount of pixels within a cell before
considering it saturated. If at the end of the loop we still have an
empty histogram, then make it a fully saturated one.

Bug: https://bugs.libcamera.org/show_bug.cgi?id=84
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
This commit is contained in:
Jean-Michel Hautbois 2021-11-04 12:19:57 +01:00
parent 5233581e51
commit 5614c95794
1 changed files with 14 additions and 2 deletions
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16
src/ipa/ipu3/algorithms/agc.cpp
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@ -63,6 +63,12 @@ static constexpr uint32_t knumHistogramBins = 256;
/* Target value to reach for the top 2% of the histogram */
static constexpr double kEvGainTarget = 0.5;
/*
* Maximum ratio of saturated pixels in a cell for the cell to be considered
* non-saturated and counted by the AGC algorithm.
*/
static constexpr uint32_t kMinCellsPerZoneRatio = 255 * 20 / 100;
Agc::Agc()
: frameCount_(0), lastFrame_(0), iqMean_(0.0), lineDuration_(0s),
minExposureLines_(0), maxExposureLines_(0), filteredExposure_(0s),
@ -124,7 +130,7 @@ void Agc::measureBrightness(const ipu3_uapi_stats_3a *stats,
&stats->awb_raw_buffer.meta_data[cellPosition]
);
if (cell->sat_ratio == 0) {
if (cell->sat_ratio <= kMinCellsPerZoneRatio) {
uint8_t gr = cell->Gr_avg;
uint8_t gb = cell->Gb_avg;
/*
@ -137,8 +143,14 @@ void Agc::measureBrightness(const ipu3_uapi_stats_3a *stats,
}
}
Histogram cumulativeHist = Histogram(Span<uint32_t>(hist));
/* Estimate the quantile mean of the top 2% of the histogram */
iqMean_ = Histogram(Span<uint32_t>(hist)).interQuantileMean(0.98, 1.0);
if (cumulativeHist.total() == 0) {
/* Force the value as histogram is empty */
iqMean_ = knumHistogramBins - 0.5;
} else {
iqMean_ = cumulativeHist.interQuantileMean(0.98, 1.0);
}
}
/**