[v2,9/9] libcamera: software_isp: Apply CCM in debayering
diff mbox series

Message ID 20241125180310.1254519-10-mzamazal@redhat.com
State New
Headers show
Series
  • Software ISP support for CCM
Related show

Commit Message

Milan Zamazal Nov. 25, 2024, 6:03 p.m. UTC
This patch applies color correction matrix (CCM) in debayering if the
CCM is specified.  Not using CCM must still be supported for performance
reasons.

The CCM is applied as follows:

            [r1 r2 r3]
  [r g b] * [g1 g2 g3]
            [b1 b2 b3]

The CCM matrix (the right side of the multiplication) is constant during
single frame processing, while the input pixel (the left side) changes.
Because each of the color channels is only 8-bit in software ISP, we can
make 9 lookup tables with 256 input values for multiplications of each
of the r_i, g_i, b_i values.  This way we don't have to multiply each
pixel, we can use table lookups and additions instead.  Gamma (which is
non-linear and thus cannot be a part of the 9 lookup tables values) is
applied on the final values rounded to integers using another lookup
table.

We use int16_t to store the precomputed multiplications.  This seems to
be noticeably (>10%) faster than `float' for the price of slightly less
accuracy and it covers the range of values that sane CCMs produce.  The
selection and structure of data is performance critical, for example
using bytes would add significant (>10%) speedup but would be too short
to cover the value range.

The color lookup tables are changed to unions to be able to serve as
both simple lookup tables or CCM lookup tables.  This is arguable but it
keeps the code easier to understand if nothing else.  It is important to
make the unions on the whole lookup tables rather than their values
because the latter might cause a noticeable slowdown on simple lookup
due to the sheer fact that the table is not compact.  Using unions makes
the initialization of the tables dubious because it is done before the
decision about using CCM is made but the initial values are dubious
anyway.

The tables are copied (as before), which is not elegant but also not a
big problem.  There are patches posted that use shared buffers for
parameters passing in software ISP (see software ISP TODO #5) and they
can be adjusted for the new parameter format.

With this patch, the reported per-frame slowdown when applying CCM is
about 45% on Debix Model A and about 75% on TI AM69 SK.

Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
---
 .../internal/software_isp/debayer_params.h    | 20 ++++++-
 src/ipa/simple/algorithms/lut.cpp             | 58 ++++++++++++++-----
 src/ipa/simple/algorithms/lut.h               |  1 +
 src/libcamera/software_isp/debayer.cpp        | 53 ++++++++++++++++-
 src/libcamera/software_isp/debayer_cpu.cpp    | 34 ++++++++---
 src/libcamera/software_isp/debayer_cpu.h      |  7 ++-
 src/libcamera/software_isp/software_isp.cpp   |  6 +-
 7 files changed, 145 insertions(+), 34 deletions(-)

Patch
diff mbox series

diff --git a/include/libcamera/internal/software_isp/debayer_params.h b/include/libcamera/internal/software_isp/debayer_params.h
index 7d8fdd481..f8731eaee 100644
--- a/include/libcamera/internal/software_isp/debayer_params.h
+++ b/include/libcamera/internal/software_isp/debayer_params.h
@@ -18,11 +18,25 @@  namespace libcamera {
 struct DebayerParams {
 	static constexpr unsigned int kRGBLookupSize = 256;
 
+	struct CcmColumn {
+		int16_t r;
+		int16_t g;
+		int16_t b;
+	};
+
 	using ColorLookupTable = std::array<uint8_t, kRGBLookupSize>;
+	using CcmLookupTable = std::array<CcmColumn, kRGBLookupSize>;
+	using GammaLookupTable = std::array<uint8_t, kRGBLookupSize>;
+
+	union LookupTable {
+		ColorLookupTable simple;
+		CcmLookupTable ccm;
+	};
 
-	ColorLookupTable red;
-	ColorLookupTable green;
-	ColorLookupTable blue;
+	LookupTable red;
+	LookupTable green;
+	LookupTable blue;
+	GammaLookupTable gammaLut;
 };
 
 } /* namespace libcamera */
diff --git a/src/ipa/simple/algorithms/lut.cpp b/src/ipa/simple/algorithms/lut.cpp
index 8fca96b0a..1d9a607b2 100644
--- a/src/ipa/simple/algorithms/lut.cpp
+++ b/src/ipa/simple/algorithms/lut.cpp
@@ -44,6 +44,11 @@  void Lut::updateGammaTable(IPAContext &context)
 	context.activeState.gamma.blackLevel = blackLevel;
 }
 
+int16_t Lut::ccmValue(unsigned int i, float ccm) const
+{
+	return std::round(i * ccm);
+}
+
 void Lut::prepare(IPAContext &context,
 		  [[maybe_unused]] const uint32_t frame,
 		  [[maybe_unused]] IPAFrameContext &frameContext,
@@ -55,27 +60,48 @@  void Lut::prepare(IPAContext &context,
 	 * observed, it's not permanently prone to minor fluctuations or
 	 * rounding errors.
 	 */
-	if (context.activeState.gamma.blackLevel != context.activeState.blc.level)
+	const bool gammaUpdateNeeded =
+		context.activeState.gamma.blackLevel != context.activeState.blc.level;
+	if (gammaUpdateNeeded)
 		updateGammaTable(context);
 
 	auto &gains = context.activeState.awb.gains;
 	auto &gammaTable = context.activeState.gamma.gammaTable;
 	const unsigned int gammaTableSize = gammaTable.size();
-
-	for (unsigned int i = 0; i < DebayerParams::kRGBLookupSize; i++) {
-		const double div = static_cast<double>(DebayerParams::kRGBLookupSize) /
-				   gammaTableSize;
-		/* Apply gamma after gain! */
-		unsigned int idx;
-		idx = std::min({ static_cast<unsigned int>(i * gains.red / div),
-				 gammaTableSize - 1 });
-		params->red[i] = gammaTable[idx];
-		idx = std::min({ static_cast<unsigned int>(i * gains.green / div),
-				 gammaTableSize - 1 });
-		params->green[i] = gammaTable[idx];
-		idx = std::min({ static_cast<unsigned int>(i * gains.blue / div),
-				 gammaTableSize - 1 });
-		params->blue[i] = gammaTable[idx];
+	const double div = static_cast<double>(DebayerParams::kRGBLookupSize) /
+			   gammaTableSize;
+
+	if (!context.activeState.ccm.enabled) {
+		for (unsigned int i = 0; i < DebayerParams::kRGBLookupSize; i++) {
+			/* Apply gamma after gain! */
+			unsigned int idx;
+			idx = std::min({ static_cast<unsigned int>(i * gains.red / div),
+					 gammaTableSize - 1 });
+			params->red.simple[i] = gammaTable[idx];
+			idx = std::min({ static_cast<unsigned int>(i * gains.green / div),
+					 gammaTableSize - 1 });
+			params->green.simple[i] = gammaTable[idx];
+			idx = std::min({ static_cast<unsigned int>(i * gains.blue / div),
+					 gammaTableSize - 1 });
+			params->blue.simple[i] = gammaTable[idx];
+		}
+	} else if (context.activeState.ccm.changed || gammaUpdateNeeded) {
+		auto &ccm = context.activeState.ccm.ccm;
+		auto &red = params->red.ccm;
+		auto &green = params->green.ccm;
+		auto &blue = params->blue.ccm;
+		for (unsigned int i = 0; i < DebayerParams::kRGBLookupSize; i++) {
+			red[i].r = ccmValue(i, ccm[0][0]);
+			red[i].g = ccmValue(i, ccm[1][0]);
+			red[i].b = ccmValue(i, ccm[2][0]);
+			green[i].r = ccmValue(i, ccm[0][1]);
+			green[i].g = ccmValue(i, ccm[1][1]);
+			green[i].b = ccmValue(i, ccm[2][1]);
+			blue[i].r = ccmValue(i, ccm[0][2]);
+			blue[i].g = ccmValue(i, ccm[1][2]);
+			blue[i].b = ccmValue(i, ccm[2][2]);
+			params->gammaLut[i] = gammaTable[i / div];
+		}
 	}
 }
 
diff --git a/src/ipa/simple/algorithms/lut.h b/src/ipa/simple/algorithms/lut.h
index b635987d0..8d50a23fc 100644
--- a/src/ipa/simple/algorithms/lut.h
+++ b/src/ipa/simple/algorithms/lut.h
@@ -27,6 +27,7 @@  public:
 
 private:
 	void updateGammaTable(IPAContext &context);
+	int16_t ccmValue(unsigned int i, float ccm) const;
 };
 
 } /* namespace ipa::soft::algorithms */
diff --git a/src/libcamera/software_isp/debayer.cpp b/src/libcamera/software_isp/debayer.cpp
index f0b832619..47f9996bb 100644
--- a/src/libcamera/software_isp/debayer.cpp
+++ b/src/libcamera/software_isp/debayer.cpp
@@ -23,11 +23,56 @@  namespace libcamera {
  * \brief Size of a color lookup table
  */
 
+/**
+ * \struct DebayerParams::CcmColumn
+ * \brief Type of a single column of a color correction matrix
+ */
+
+/**
+ * \var DebayerParams::CcmColumn::r
+ * \brief Red (first) component of a CCM column
+ */
+
+/**
+ * \var DebayerParams::CcmColumn::g
+ * \brief Green (second) component of a CCM column
+ */
+
+/**
+ * \var DebayerParams::CcmColumn::b
+ * \brief Blue (third) component of a CCM column
+ */
+
 /**
  * \typedef DebayerParams::ColorLookupTable
+ * \brief Type of the simple lookup tables for red, green, blue values
+ */
+
+/**
+ * \typedef DebayerParams::CcmLookupTable
+ * \brief Type of the CCM lookup tables for red, green, blue values
+ */
+
+/**
+ * \typedef DebayerParams::GammaLookupTable
+ * \brief Type of the gamma lookup tables for CCM
+ */
+
+/**
+ * \union DebayerParams::LookupTable
  * \brief Type of the lookup tables for red, green, blue values
  */
 
+/**
+ * \var DebayerParams::LookupTable::simple
+ * \brief Simple lookup table for red, green, blue values
+ */
+
+/**
+ * \var DebayerParams::LookupTable::ccm
+ * \brief CCM lookup table for red, green, blue values
+ */
+
 /**
  * \var DebayerParams::red
  * \brief Lookup table for red color, mapping input values to output values
@@ -43,6 +88,11 @@  namespace libcamera {
  * \brief Lookup table for blue color, mapping input values to output values
  */
 
+/**
+ * \var DebayerParams::gammaLut
+ * \brief Gamma lookup table used with color correction matrix
+ */
+
 /**
  * \class Debayer
  * \brief Base debayering class
@@ -57,10 +107,11 @@  Debayer::~Debayer()
 }
 
 /**
- * \fn int Debayer::configure(const StreamConfiguration &inputCfg, const std::vector<std::reference_wrapper<StreamConfiguration>> &outputCfgs)
+ * \fn int Debayer::configure(const StreamConfiguration &inputCfg, const std::vector<std::reference_wrapper<StreamConfiguration>> &outputCfgs, ccmEnabled)
  * \brief Configure the debayer object according to the passed in parameters
  * \param[in] inputCfg The input configuration
  * \param[in] outputCfgs The output configurations
+ * \param[in] ccmEnabled Whether a color correction matrix is applied
  *
  * \return 0 on success, a negative errno on failure
  */
diff --git a/src/libcamera/software_isp/debayer_cpu.cpp b/src/libcamera/software_isp/debayer_cpu.cpp
index 92f81baf2..30bd1991c 100644
--- a/src/libcamera/software_isp/debayer_cpu.cpp
+++ b/src/libcamera/software_isp/debayer_cpu.cpp
@@ -11,6 +11,7 @@ 
 
 #include "debayer_cpu.h"
 
+#include <algorithm>
 #include <stdlib.h>
 #include <sys/ioctl.h>
 #include <time.h>
@@ -50,8 +51,12 @@  DebayerCpu::DebayerCpu(std::unique_ptr<SwStatsCpu> stats)
 	enableInputMemcpy_ = true;
 
 	/* Initialize color lookup tables */
-	for (unsigned int i = 0; i < DebayerParams::kRGBLookupSize; i++)
-		red_[i] = green_[i] = blue_[i] = i;
+	for (unsigned int i = 0; i < DebayerParams::kRGBLookupSize; i++) {
+		red_.simple[i] = green_.simple[i] = blue_.simple[i] = i;
+		red_.ccm[i].r = red_.ccm[i].g = red_.ccm[i].b = 0;
+		green_.ccm[i].r = green_.ccm[i].g = green_.ccm[i].b = 0;
+		blue_.ccm[i].r = blue_.ccm[i].g = blue_.ccm[i].b = 0;
+	}
 }
 
 DebayerCpu::~DebayerCpu() = default;
@@ -61,12 +66,24 @@  DebayerCpu::~DebayerCpu() = default;
 	const pixel_t *curr = (const pixel_t *)src[1] + xShift_; \
 	const pixel_t *next = (const pixel_t *)src[2] + xShift_;
 
-#define STORE_PIXEL(b, g, r)        \
-	*dst++ = blue_[b];          \
-	*dst++ = green_[g];         \
-	*dst++ = red_[r];           \
-	if constexpr (addAlphaByte) \
-		*dst++ = 255;       \
+#define GAMMA(value) \
+	*dst++ = gammaLut_[std::clamp(value, 0, static_cast<int>(gammaLut_.size()) - 1)]
+
+#define STORE_PIXEL(b_, g_, r_)                                   \
+	if constexpr (ccmEnabled) {                               \
+		DebayerParams::CcmColumn &blue = blue_.ccm[b_];   \
+		DebayerParams::CcmColumn &green = green_.ccm[g_]; \
+		DebayerParams::CcmColumn &red = red_.ccm[r_];     \
+		GAMMA(blue.r + blue.g + blue.b);                  \
+		GAMMA(green.r + green.g + green.b);               \
+		GAMMA(red.r + red.g + red.b);                     \
+	} else {                                                  \
+		*dst++ = blue_.simple[b_];                        \
+		*dst++ = green_.simple[g_];                       \
+		*dst++ = red_.simple[r_];                         \
+	}                                                         \
+	if constexpr (addAlphaByte)                               \
+		*dst++ = 255;                                     \
 	x++;
 
 /*
@@ -764,6 +781,7 @@  void DebayerCpu::process(uint32_t frame, FrameBuffer *input, FrameBuffer *output
 	green_ = params.green;
 	red_ = swapRedBlueGains_ ? params.blue : params.red;
 	blue_ = swapRedBlueGains_ ? params.red : params.blue;
+	gammaLut_ = params.gammaLut;
 
 	/* Copy metadata from the input buffer */
 	FrameMetadata &metadata = output->_d()->metadata();
diff --git a/src/libcamera/software_isp/debayer_cpu.h b/src/libcamera/software_isp/debayer_cpu.h
index b2ec8f1bd..35c51e4fd 100644
--- a/src/libcamera/software_isp/debayer_cpu.h
+++ b/src/libcamera/software_isp/debayer_cpu.h
@@ -137,9 +137,10 @@  private:
 	/* Max. supported Bayer pattern height is 4, debayering this requires 5 lines */
 	static constexpr unsigned int kMaxLineBuffers = 5;
 
-	DebayerParams::ColorLookupTable red_;
-	DebayerParams::ColorLookupTable green_;
-	DebayerParams::ColorLookupTable blue_;
+	DebayerParams::LookupTable red_;
+	DebayerParams::LookupTable green_;
+	DebayerParams::LookupTable blue_;
+	DebayerParams::GammaLookupTable gammaLut_;
 	debayerFn debayer0_;
 	debayerFn debayer1_;
 	debayerFn debayer2_;
diff --git a/src/libcamera/software_isp/software_isp.cpp b/src/libcamera/software_isp/software_isp.cpp
index 0e1d3a457..08eca192e 100644
--- a/src/libcamera/software_isp/software_isp.cpp
+++ b/src/libcamera/software_isp/software_isp.cpp
@@ -79,9 +79,9 @@  SoftwareIsp::SoftwareIsp(PipelineHandler *pipe, const CameraSensor *sensor)
 	for (unsigned int i = 0; i < 256; i++)
 		gammaTable[i] = UINT8_MAX * std::pow(i / 256.0, 0.5);
 	for (unsigned int i = 0; i < DebayerParams::kRGBLookupSize; i++) {
-		debayerParams_.red[i] = gammaTable[i];
-		debayerParams_.green[i] = gammaTable[i];
-		debayerParams_.blue[i] = gammaTable[i];
+		debayerParams_.red.simple[i] = gammaTable[i];
+		debayerParams_.green.simple[i] = gammaTable[i];
+		debayerParams_.blue.simple[i] = gammaTable[i];
 	}
 
 	if (!dmaHeap_.isValid()) {