[PATCH v5] ipa: rkisp1: Add a helper to convert floating-point to fixed-point
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Sun Jun 2 02:05:18 CEST 2024
Hi Paul,
Thank you for the patch, and sorry for the late review.
On Fri, May 31, 2024 at 03:51:21PM +0900, Paul Elder wrote:
> Add helper functions for converting between floating point and fixed
> point numbers. Also add tests for them.
>
> Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
> Reviewed-by: Stefan Klug <stefan.klug at ideasonboard.com>
> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
>
> ---
> Changes in v5:
> - fix test comments
> - add documentation for the actual parameters (only template parameters
> were documented previously)
>
> Changes in v4:
> - relax the test case floating point precision
> - optimize the fixed -> floating point converter
>
> Changes in v3:
> - (used to be "libcamera: utils: Add a helper to convert floating-point to fixed-point")
> - move the everything from libcamera global utils to the rkisp1 ipa
>
> Changes in v2:
> - added the reverse conversion function (fixed -> floating)
> - added tests
> - make the conversion code cleaner
> ---
> src/ipa/rkisp1/meson.build | 1 +
> src/ipa/rkisp1/utils.cpp | 42 +++++++++++++++
> src/ipa/rkisp1/utils.h | 66 ++++++++++++++++++++++++
> test/ipa/meson.build | 2 +
> test/ipa/rkisp1/meson.build | 15 ++++++
> test/ipa/rkisp1/rkisp1-utils.cpp | 87 ++++++++++++++++++++++++++++++++
> 6 files changed, 213 insertions(+)
> create mode 100644 src/ipa/rkisp1/utils.cpp
> create mode 100644 src/ipa/rkisp1/utils.h
> create mode 100644 test/ipa/rkisp1/meson.build
> create mode 100644 test/ipa/rkisp1/rkisp1-utils.cpp
>
> diff --git a/src/ipa/rkisp1/meson.build b/src/ipa/rkisp1/meson.build
> index e813da53a..cf05cdb27 100644
> --- a/src/ipa/rkisp1/meson.build
> +++ b/src/ipa/rkisp1/meson.build
> @@ -8,6 +8,7 @@ ipa_name = 'ipa_rkisp1'
> rkisp1_ipa_sources = files([
> 'ipa_context.cpp',
> 'rkisp1.cpp',
> + 'utils.cpp',
> ])
>
> rkisp1_ipa_sources += rkisp1_ipa_algorithms
> diff --git a/src/ipa/rkisp1/utils.cpp b/src/ipa/rkisp1/utils.cpp
> new file mode 100644
> index 000000000..960ec64e9
> --- /dev/null
> +++ b/src/ipa/rkisp1/utils.cpp
> @@ -0,0 +1,42 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2024, Paul Elder <paul.elder at ideasonboard.com>
> + *
> + * Miscellaneous utility functions specific to rkisp1
> + */
> +
> +#include "utils.h"
> +
> +/**
> + * \file utils.h
Missing \brief
> + */
> +
> +namespace libcamera {
> +
> +namespace ipa::rkisp1::utils {
> +
> +/**
> + * \fn R floatingToFixedPoint(T number)
> + * \brief Convert a floating point number to a fixed-point representation
> + * \tparam I Bit width of the integer part of the fixed-point
> + * \tparam F Bit width of the fractional part of the fixed-point
> + * \tparam R Return type of the fixed-point representation
> + * \tparam T Input type of the floating point representation
> + * \param number The floating point number to convert to fixed point
> + * \return The converted value
> + */
> +
> +/**
> + * \fn R fixedToFloatingPoint(T number)
> + * \brief Convert a fixed-point number to a floating point representation
> + * \tparam I Bit width of the integer part of the fixed-point
> + * \tparam F Bit width of the fractional part of the fixed-point
> + * \tparam R Return type of the floating point representation
> + * \tparam T Input type of the fixed-point representation
> + * \param number The fixed point number to convert to floating point
> + * \return The converted value
> + */
> +
> +} /* namespace ipa::rkisp1::utils */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/rkisp1/utils.h b/src/ipa/rkisp1/utils.h
> new file mode 100644
> index 000000000..450f22442
> --- /dev/null
> +++ b/src/ipa/rkisp1/utils.h
> @@ -0,0 +1,66 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2024, Paul Elder <paul.elder at ideasonboard.com>
> + *
> + * Miscellaneous utility functions specific to rkisp1
> + */
> +
> +#pragma once
> +
> +#include <cmath>
> +#include <limits>
> +#include <type_traits>
> +
> +namespace libcamera {
> +
> +namespace ipa::rkisp1::utils {
> +
> +#ifndef __DOXYGEN__
> +template<unsigned int I, unsigned int F, typename R, typename T,
> + std::enable_if_t<std::is_integral_v<R> &&
> + std::is_floating_point_v<T>> * = nullptr>
> +#else
> +template<unsigned int I, unsigned int F, typename R, typename T>
> +#endif
> +constexpr R floatingToFixedPoint(T number)
> +{
> + static_assert(sizeof(int) >= sizeof(R));
> + static_assert(I + F <= sizeof(R) * 8);
> +
> + /*
> + * The intermediate cast to int is needed on arm platforms to properly
> + * cast negative values. See
> + * https://embeddeduse.com/2013/08/25/casting-a-negative-float-to-an-unsigned-int/
> + */
> + R mask = (1 << (F + I)) - 1;
> + R frac = static_cast<R>(static_cast<int>(std::round(number * (1 << F)))) & mask;
> +
> + return frac;
> +}
> +
> +#ifndef __DOXYGEN__
> +template<unsigned int I, unsigned int F, typename R, typename T,
> + std::enable_if_t<std::is_floating_point_v<R> &&
> + std::is_integral_v<T>> * = nullptr>
> +#else
> +template<unsigned int I, unsigned int F, typename R, typename T>
> +#endif
> +constexpr R fixedToFloatingPoint(T number)
> +{
> + static_assert(sizeof(int) >= sizeof(T));
> + static_assert(I + F <= sizeof(T) * 8);
> +
> + /*
> + * Recreate the upper bits in case of a negative number by shifting the sign
> + * bit from the fixed point to the first bit of the unsigned and then right shifting
> + * by the same amount which keeps the sign bit in place.
> + * This can be optimized by the compiler quite well.
> + */
> + int remaining_bits = sizeof(int) * 8 - (I + F);
> + int t = static_cast<int>(static_cast<unsigned>(number) << remaining_bits) >> remaining_bits;
> + return static_cast<R>(t) / static_cast<R>(1 << F);
> +}
> +
> +} /* namespace ipa::rkisp1::utils */
> +
> +} /* namespace libcamera */
> diff --git a/test/ipa/meson.build b/test/ipa/meson.build
> index 180b0da0a..dc956284c 100644
> --- a/test/ipa/meson.build
> +++ b/test/ipa/meson.build
> @@ -1,5 +1,7 @@
> # SPDX-License-Identifier: CC0-1.0
>
> +subdir('rkisp1')
> +
> ipa_test = [
> {'name': 'ipa_module_test', 'sources': ['ipa_module_test.cpp']},
> {'name': 'ipa_interface_test', 'sources': ['ipa_interface_test.cpp']},
> diff --git a/test/ipa/rkisp1/meson.build b/test/ipa/rkisp1/meson.build
> new file mode 100644
> index 000000000..5ffc5dd60
> --- /dev/null
> +++ b/test/ipa/rkisp1/meson.build
> @@ -0,0 +1,15 @@
> +# SPDX-License-Identifier: CC0-1.0
> +
> +rkisp1_ipa_test = [
> + {'name': 'rkisp1-utils', 'sources': ['rkisp1-utils.cpp']},
> +]
> +
> +foreach test : rkisp1_ipa_test
> + exe = executable(test['name'], test['sources'], libcamera_generated_ipa_headers,
> + dependencies : libcamera_private,
> + link_with : [libipa, test_libraries],
> + include_directories : [libipa_includes, test_includes_internal,
> + '../../../src/ipa/rkisp1/'])
> +
> + test(test['name'], exe, suite : 'ipa')
> +endforeach
> diff --git a/test/ipa/rkisp1/rkisp1-utils.cpp b/test/ipa/rkisp1/rkisp1-utils.cpp
> new file mode 100644
> index 000000000..ed6f44e9b
> --- /dev/null
> +++ b/test/ipa/rkisp1/rkisp1-utils.cpp
> @@ -0,0 +1,87 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Copyright (C) 2024, Paul Elder <paul.elder at ideasonboard.com>
> + *
> + * Miscellaneous utility tests
> + */
> +
> +#include <cmath>
> +#include <iostream>
> +#include <map>
> +
> +#include "../src/ipa/rkisp1/utils.h"
> +
> +#include "test.h"
> +
> +using namespace std;
> +using namespace libcamera;
> +using namespace ipa::rkisp1;
> +
> +class RkISP1UtilsTest : public Test
> +{
> +protected:
> + template<unsigned int intPrec, unsigned fracPrec, typename T>
> + int testSingleFixedPoint(double input, T expected)
> + {
> + T ret = utils::floatingToFixedPoint<intPrec, fracPrec, T>(input);
> + if (ret != expected) {
> + cerr << "Expected " << input << " to convert to "
> + << expected << ", got " << ret << std::endl;
> + return TestFail;
> + }
> +
> + /*
> + * The precision check is fairly arbitrary but is based on what
> + * the rkisp1 is capable of in the crosstalk module.
Shouldn't it be based on the fracPrec value instead ?
> + */
> + double f = utils::fixedToFloatingPoint<intPrec, fracPrec, double>(ret);
> + if (std::abs(f - input) > 0.005) {
> + cerr << "Reverse conversion expected " << ret
> + << " to convert to " << input
> + << ", got " << f << std::endl;
> + return TestFail;
> + }
> +
> + return TestPass;
> + }
> +
> + int testFixedPoint()
> + {
> + /*
> + * The second 7.992 test is to test that unused bits don't
> + * affect the result.
> + */
> + std::map<double, uint16_t> testCases = {
> + { 7.992, 0x3FF },
> + { 7.992, 0xBFF },
I had a bit of a WTF moment, not understanding how the same double could
convert to two different fixed point values. Then I realized you're
using a std::map here, which doesn't support multiple items with the
same key.
What you need is a
std::vector<std::pair<double, uint16_t>> testCases = {
(don't forget to include vector and utility instead of map). With that,
the test will fail.
As this patch has been merged already, could you send patches to fix
those issues ?
> + { 0.2, 0x01A },
> + { -0.2, 0x7E6 },
> + { -0.8, 0x79A },
> + { -0.4, 0x7CD },
> + { -1.4, 0x74D },
> + { -8, 0x400 },
> + { 0, 0 },
> + };
> +
> + int ret;
> + for (const auto &testCase : testCases) {
> + ret = testSingleFixedPoint<4, 7, uint16_t>(testCase.first,
> + testCase.second);
> + if (ret != TestPass)
> + return ret;
> + }
> +
> + return TestPass;
> + }
> +
> + int run()
> + {
> + /* fixed point conversion test */
> + if (testFixedPoint() != TestPass)
> + return TestFail;
> +
> + return TestPass;
> + }
> +};
> +
> +TEST_REGISTER(RkISP1UtilsTest)
--
Regards,
Laurent Pinchart
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