[libcamera-devel,v5,26/33] ipa: rkisp1: awb: Use frame context to fix gains calculations
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Message ID 20220927023642.12341-27-laurent.pinchart@ideasonboard.com
State Accepted
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Series
  • ipa: Frame context queue, IPU3 & RkISP consolidation, and RkISP1 improvements
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Commit Message

Laurent Pinchart Sept. 27, 2022, 2:36 a.m. UTC 
The AWB statistics are computed after the ISP applies the colour gains.
This means that the red, green and blue means do not match the data
coming directly from the sensor, but are multiplied by the colour gains
that were used for the frame on which the statistics have been computed.
The AWB algorithm needs to take this into account when calculating the
colour gains for the next frame. Do so by dividing the means by the
gains that were applied to the frame, retrieved from the frame context.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
---
 src/ipa/rkisp1/algorithms/awb.cpp | 9 +++++++++
 1 file changed, 9 insertions(+)

Patch
diff mbox series 

diff --git a/src/ipa/rkisp1/algorithms/awb.cpp b/src/ipa/rkisp1/algorithms/awb.cpp
index e491cf7507e0..694d97cccc07 100644
--- a/src/ipa/rkisp1/algorithms/awb.cpp
+++ b/src/ipa/rkisp1/algorithms/awb.cpp
@@ -207,6 +207,15 @@  void Awb::process(IPAContext &context,
 	double greenMean = 1.1636 * yMean - 0.4045 * cbMean - 0.7949 * crMean;
 	double blueMean = 1.1636 * yMean + 1.9912 * cbMean - 0.0250 * crMean;
 
+	/*
+	 * The ISP computes the AWB means after applying the colour gains,
+	 * divide by the gains that were used to get the raw means from the
+	 * sensor.
+	 */
+	redMean /= frameContext.awb.gains.red;
+	greenMean /= frameContext.awb.gains.green;
+	blueMean /= frameContext.awb.gains.blue;
+
 	frameContext.awb.temperatureK = estimateCCT(redMean, greenMean, blueMean);
 
 	/* Estimate the red and blue gains to apply in a grey world. */