[PATCH 9/9] libcamera: software_isp: Apply CCM in debayering
Robert Mader
robert.mader at collabora.com
Sun Nov 24 17:13:16 CET 2024
There's a red <-> blue color swap when the ccm is active, see below:
On 20.11.24 19:01, Milan Zamazal wrote:
> 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 85% on TI AM69 SK.
>
> Signed-off-by: Milan Zamazal<mzamazal at 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(-)
>
> diff --git a/include/libcamera/internal/software_isp/debayer_params.h b/include/libcamera/internal/software_isp/debayer_params.h
> index 7d8fdd481..531db6968 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 CcmRow {
> + int16_t c1;
> + int16_t c2;
> + int16_t c3;
> + };
> +
> using ColorLookupTable = std::array<uint8_t, kRGBLookupSize>;
> + using CcmLookupTable = std::array<CcmRow, 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..259976e08 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].c1 = ccmValue(i, ccm[0][0]);
> + red[i].c2 = ccmValue(i, ccm[0][1]);
> + red[i].c3 = ccmValue(i, ccm[0][2]);
> + green[i].c1 = ccmValue(i, ccm[1][0]);
> + green[i].c2 = ccmValue(i, ccm[1][1]);
> + green[i].c3 = ccmValue(i, ccm[1][2]);
> + blue[i].c1 = ccmValue(i, ccm[2][0]);
> + blue[i].c2 = ccmValue(i, ccm[2][1]);
> + blue[i].c3 = 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..97106b22b 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::CcmRow
> + * \brief Type of a single row of a color correction matrix
> + */
> +
> +/**
> + * \var DebayerParams::CcmRow::c1
> + * \brief First column of a CCM row
> + */
> +
> +/**
> + * \var DebayerParams::CcmRow::c2
> + * \brief Second column of a CCM row
> + */
> +
> +/**
> + * \var DebayerParams::CcmRow::c3
> + * \brief Third column of a CCM row
> + */
> +
> /**
> * \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 52baf43dc..d8976f183 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].c1 = red_.ccm[i].c2 = red_.ccm[i].c3 = 0;
> + green_.ccm[i].c1 = green_.ccm[i].c2 = green_.ccm[i].c3 = 0;
> + blue_.ccm[i].c1 = blue_.ccm[i].c2 = blue_.ccm[i].c3 = 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_[r]; \
> - *dst++ = green_[g]; \
> - *dst++ = red_[b]; \
> - if constexpr (addAlphaByte) \
> - *dst++ = 255; \
> +#define GAMMA(value) \
> + *dst++ = gammaLut_[std::clamp(value, 0, 1023)]
> +
> +#define STORE_PIXEL(b, g, r) \
> + if constexpr (ccmEnabled) { \
> + DebayerParams::CcmRow &red = red_.ccm[r]; \
> + DebayerParams::CcmRow &green = green_.ccm[g]; \
> + DebayerParams::CcmRow &blue = blue_.ccm[b]; \
> + GAMMA(red.c3 + green.c3 + blue.c3); \
> + GAMMA(red.c2 + green.c2 + blue.c2); \
> + GAMMA(red.c1 + green.c1 + blue.c1); \
This apparently should be:
+ GAMMA(red.c1 + green.c1 + blue.c1); \
+ GAMMA(red.c2 + green.c2 + blue.c2); \
+ GAMMA(red.c3 + green.c3 + blue.c3); \
> + } 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()) {
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