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ipa: ipu3: awb: Correct the gains calculation

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The factor used right now in the IPU3 is 8192, as a multiplier of the
estimated gain. This is wrong, as the isp is adding 1.0 to the gain
applied, ie Pout = { Pin * (1 + Gx) }.

Fix it, and to ease the reading, introduce a small helper function.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
This commit is contained in:
Jean-Michel Hautbois 2022-06-15 16:57:43 +02:00
parent d2c097c482
commit 4bb284e0fa
2 changed files with 23 additions and 5 deletions
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27
src/ipa/ipu3/algorithms/awb.cpp
View file

@ -409,6 +409,23 @@ constexpr uint16_t Awb::threshold(float value)
return value * 8191;
}
constexpr uint16_t Awb::gainValue(double gain)
{
/*
* The colour gains applied by the BNR for the four channels (Gr, R, B
* and Gb) are expressed in the parameters structure as 16-bit integers
* that store a fixed-point U3.13 value in the range [0, 8[.
*
* The real gain value is equal to the gain parameter plus one, i.e.
*
* Pout = Pin * (1 + gain / 8192)
*
* where 'Pin' is the input pixel value, 'Pout' the output pixel value,
* and 'gain' the gain in the parameters structure as a 16-bit integer.
*/
return std::clamp((gain - 1.0) * 8192, 0.0, 65535.0);
}
/**
* \copydoc libcamera::ipa::Algorithm::prepare
*/
@ -450,11 +467,11 @@ void Awb::prepare(IPAContext &context, ipu3_uapi_params *params)
* params->acc_param.bnr.opt_center.x_reset;
params->acc_param.bnr.opt_center_sqr.y_sqr_reset = params->acc_param.bnr.opt_center.y_reset
* params->acc_param.bnr.opt_center.y_reset;
/* Convert to u3.13 fixed point values */
params->acc_param.bnr.wb_gains.gr = 8192 * context.activeState.awb.gains.green;
params->acc_param.bnr.wb_gains.r = 8192 * context.activeState.awb.gains.red;
params->acc_param.bnr.wb_gains.b = 8192 * context.activeState.awb.gains.blue;
params->acc_param.bnr.wb_gains.gb = 8192 * context.activeState.awb.gains.green;
params->acc_param.bnr.wb_gains.gr = gainValue(context.activeState.awb.gains.green);
params->acc_param.bnr.wb_gains.r = gainValue(context.activeState.awb.gains.red);
params->acc_param.bnr.wb_gains.b = gainValue(context.activeState.awb.gains.blue);
params->acc_param.bnr.wb_gains.gb = gainValue(context.activeState.awb.gains.green);
LOG(IPU3Awb, Debug) << "Color temperature estimated: " << asyncResults_.temperatureK;

1
src/ipa/ipu3/algorithms/awb.h
View file

@ -73,6 +73,7 @@ private:
void awbGreyWorld();
uint32_t estimateCCT(double red, double green, double blue);
static constexpr uint16_t threshold(float value);
static constexpr uint16_t gainValue(double gain);
std::vector<RGB> zones_;
Accumulator awbStats_[kAwbStatsSizeX * kAwbStatsSizeY];