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-rw-r--r--src/ipa/libipa/camera_sensor_helper.cpp82
-rw-r--r--src/ipa/libipa/camera_sensor_helper.h6
2 files changed, 67 insertions, 21 deletions
diff --git a/src/ipa/libipa/camera_sensor_helper.cpp b/src/ipa/libipa/camera_sensor_helper.cpp
index 714cd86f..7bb999e1 100644
--- a/src/ipa/libipa/camera_sensor_helper.cpp
+++ b/src/ipa/libipa/camera_sensor_helper.cpp
@@ -7,6 +7,8 @@
*/
#include "camera_sensor_helper.h"
+#include <cmath>
+
#include <libcamera/base/log.h>
/**
@@ -51,20 +53,28 @@ namespace ipa {
* This function aims to abstract the calculation of the gain letting the IPA
* use the real gain for its estimations.
*
- * The parameters come from the MIPI Alliance Camera Specification for
- * Camera Command Set (CCS).
- *
* \return The gain code to pass to V4L2
*/
uint32_t CameraSensorHelper::gainCode(double gain) const
{
const AnalogueGainConstants &k = gainConstants_;
- ASSERT(gainType_ == AnalogueGainLinear);
- ASSERT(k.linear.m0 == 0 || k.linear.m1 == 0);
+ switch (gainType_) {
+ case AnalogueGainLinear:
+ ASSERT(k.linear.m0 == 0 || k.linear.m1 == 0);
+
+ return (k.linear.c0 - k.linear.c1 * gain) /
+ (k.linear.m1 * gain - k.linear.m0);
- return (k.linear.c0 - k.linear.c1 * gain) /
- (k.linear.m1 * gain - k.linear.m0);
+ case AnalogueGainExponential:
+ ASSERT(k.exp.a != 0 && k.exp.m != 0);
+
+ return std::log2(gain / k.exp.a) / k.exp.m;
+
+ default:
+ ASSERT(false);
+ return 0;
+ }
}
/**
@@ -75,20 +85,29 @@ uint32_t CameraSensorHelper::gainCode(double gain) const
* use the real gain for its estimations. It is the counterpart of the function
* CameraSensorHelper::gainCode.
*
- * The parameters come from the MIPI Alliance Camera Specification for
- * Camera Command Set (CCS).
- *
* \return The real gain
*/
double CameraSensorHelper::gain(uint32_t gainCode) const
{
const AnalogueGainConstants &k = gainConstants_;
+ double gain = static_cast<double>(gainCode);
+
+ switch (gainType_) {
+ case AnalogueGainLinear:
+ ASSERT(k.linear.m0 == 0 || k.linear.m1 == 0);
+
+ return (k.linear.m0 * gain + k.linear.c0) /
+ (k.linear.m1 * gain + k.linear.c1);
- ASSERT(gainType_ == AnalogueGainLinear);
- ASSERT(k.linear.m0 == 0 || k.linear.m1 == 0);
+ case AnalogueGainExponential:
+ ASSERT(k.exp.a != 0 && k.exp.m != 0);
- return (k.linear.m0 * static_cast<double>(gainCode) + k.linear.c0) /
- (k.linear.m1 * static_cast<double>(gainCode) + k.linear.c1);
+ return k.exp.a * std::exp2(k.exp.m * gain);
+
+ default:
+ ASSERT(false);
+ return 0.0;
+ }
}
/**
@@ -120,15 +139,22 @@ double CameraSensorHelper::gain(uint32_t gainCode) const
/**
* \var CameraSensorHelper::AnalogueGainExponential
- * \brief Gain is computed using exponential gain estimation
- * (introduced in CCS v1.1)
+ * \brief Gain is expressed using an exponential model
*
- * Starting with CCS v1.1, Alternate Global Analogue Gain is also available.
- * If the image sensor supports it, then the global analogue gain can be
- * controlled by linear and exponential gain formula:
+ * The relationship between the integer gain parameter and the resulting gain
+ * multiplier is given by the following equation:
+ *
+ * \f$gain = a \cdot 2^{m \cdot x}\f$
*
- * \f$gain = analogLinearGainGlobal * 2^{analogExponentialGainGlobal}\f$
- * \todo not implemented in libipa
+ * Where 'x' is the gain control parameter, and 'a' and 'm' are image
+ * sensor-specific constants.
+ *
+ * This is a subset of the MIPI CCS exponential gain model with the linear
+ * factor 'a' being a constant, but with the exponent being configurable
+ * through the 'm' coefficient.
+ *
+ * When the gain is expressed in dB, 'a' is equal to 1 and 'm' to
+ * \f$log_{2}{10^{frac{1}{20}}}\f$.
*/
/**
@@ -153,6 +179,17 @@ double CameraSensorHelper::gain(uint32_t gainCode) const
*/
/**
+ * \struct CameraSensorHelper::AnalogueGainExpConstants
+ * \brief Analogue gain constants for the exponential gain model
+ *
+ * \var CameraSensorHelper::AnalogueGainExpConstants::a
+ * \brief Constant used in the exponential gain coding/decoding
+ *
+ * \var CameraSensorHelper::AnalogueGainExpConstants::m
+ * \brief Constant used in the exponential gain coding/decoding
+ */
+
+/**
* \struct CameraSensorHelper::AnalogueGainConstants
* \brief Analogue gain model constants
*
@@ -161,6 +198,9 @@ double CameraSensorHelper::gain(uint32_t gainCode) const
*
* \var CameraSensorHelper::AnalogueGainConstants::linear
* \brief Constants for the linear gain model
+ *
+ * \var CameraSensorHelper::AnalogueGainConstants::exp
+ * \brief Constants for the exponential gain model
*/
/**
diff --git a/src/ipa/libipa/camera_sensor_helper.h b/src/ipa/libipa/camera_sensor_helper.h
index 6b96520b..7351fc7c 100644
--- a/src/ipa/libipa/camera_sensor_helper.h
+++ b/src/ipa/libipa/camera_sensor_helper.h
@@ -41,8 +41,14 @@ protected:
int16_t c1;
};
+ struct AnalogueGainExpConstants {
+ double a;
+ double m;
+ };
+
union AnalogueGainConstants {
AnalogueGainLinearConstants linear;
+ AnalogueGainExpConstants exp;
};
AnalogueGainType gainType_;