ipa: rkisp1: Damp color temperature regulation

Damp the regulation of the color temperature with the same factor as the
gains.  Not damping the color temperature leads to visible flicker, as
the CCM changes too much.

Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>

src/ipa/rkisp1/algorithms/awb.cpp

@@ -324,8 +324,6 @@ void Awb::process(IPAContext &context,
 	RkISP1AwbStats awbStats{ rgbMeans };
 	AwbResult awbResult = awbAlgo_->calculateAwb(awbStats, frameContext.lux.lux);
 
-	activeState.awb.automatic.temperatureK = awbResult.colourTemperature;
-
 	/*
 	 * Clamp the gain values to the hardware, which expresses gains as Q2.8
 	 * unsigned integer values. Set the minimum just above zero to avoid
@@ -336,9 +334,12 @@ void Awb::process(IPAContext &context,
 
 	/* Filter the values to avoid oscillations. */
 	double speed = 0.2;
+	double ct = awbResult.colourTemperature;
+	ct = ct * speed + activeState.awb.automatic.temperatureK * (1 - speed);
 	awbResult.gains = awbResult.gains * speed +
 			  activeState.awb.automatic.gains * (1 - speed);
 
+	activeState.awb.automatic.temperatureK = static_cast<unsigned int>(ct);
 	activeState.awb.automatic.gains = awbResult.gains;
 
 	LOG(RkISP1Awb, Debug)

src/ipa/rkisp1/algorithms/ccm.cpp

@@ -142,10 +142,6 @@ void Ccm::prepare(IPAContext &context, const uint32_t frame,
 	}
 
 	uint32_t ct = frameContext.awb.temperatureK;
-	/*
-	 * \todo The colour temperature will likely be noisy, add filtering to
-	 * avoid updating the CCM matrix all the time.
-	 */
 	if (frame > 0 && ct == ct_) {
 		frameContext.ccm.ccm = context.activeState.ccm.automatic;
 		return;