Add methods to get oversampler factor given in/out rates

devtools/HIIRDesigner.cpp

@@ -152,6 +152,7 @@ static void generate_cpp_prologue(int argc, char *argv[])
     printf(
         "#pragma once\n"
         "#include \"OversamplerHelpers.h\"\n"
+        "#include \"MathHelpers\"\n"
         "\n"
         "namespace sfz {\n"
         );
@@ -209,6 +210,14 @@ static void generate_cpp_upsampler(const Stage *stages, int num_stages)
     printf("\t\t" "}\n");
     printf("\t" "}\n");
 
+    printf("\t" "static unsigned conversionFactor(double sourceRate, double targetRate)\n");
+    printf("\t" "{\n");
+    printf("\t\t" "int factor = static_cast<int>(std::ceil(targetRate / sourceRate));\n");
+    printf("\t\t" "factor = (factor > 1) ? factor : 1;\n");
+    printf("\t\t" "factor = (factor < 128) ? factor : 128;\n");
+    printf("\t\t" "return nextPow2(factor);\n");
+    printf("\t" "}\n");
+
     printf("\t" "static bool canProcess(int factor)\n");
     printf("\t" "{\n");
     printf("\t\t" "switch (factor) {\n");
@@ -322,6 +331,14 @@ static void generate_cpp_downsampler(const Stage *stages, int num_stages)
     printf("\t\t" "}\n");
     printf("\t" "}\n");
 
+    printf("\t" "static unsigned conversionFactor(double sourceRate, double targetRate)\n");
+    printf("\t" "{\n");
+    printf("\t\t" "int factor = static_cast<int>(std::ceil(targetRate / sourceRate));\n");
+    printf("\t\t" "factor = (factor > 1) ? factor : 1;\n");
+    printf("\t\t" "factor = (factor < 128) ? factor : 128;\n");
+    printf("\t\t" "return nextPow2(factor);\n");
+    printf("\t" "}\n");
+
     printf("\t" "static bool canProcess(int factor)\n");
     printf("\t" "{\n");
     printf("\t\t" "switch (factor) {\n");

src/CMakeLists.txt

@@ -263,8 +263,8 @@ add_library(sfizz::internal ALIAS sfizz_internal)
 target_sources(sfizz_internal PRIVATE ${SFIZZ_HEADERS} ${SFIZZ_SOURCES} ${FAUST_FILES})
 target_include_directories(sfizz_internal PUBLIC "." "sfizz")
 target_link_libraries(sfizz_internal
-    PUBLIC absl::strings absl::span sfizz::filesystem sfizz::atomic_queue sfizz::spin_mutex sfizz::bit_array sfizz::simde
+    PUBLIC absl::strings absl::span sfizz::filesystem sfizz::atomic_queue sfizz::spin_mutex sfizz::bit_array sfizz::simde sfizz::hiir
-    PRIVATE sfizz::parser sfizz::messaging absl::flat_hash_map Threads::Threads st_audiofile sfizz::pugixml sfizz::spline sfizz::tunings sfizz::hiir sfizz::kissfft sfizz::cephes sfizz::cpuid sfizz::threadpool sfizz::jsl sfizz::atomic)
+    PRIVATE sfizz::parser sfizz::messaging absl::flat_hash_map Threads::Threads st_audiofile sfizz::pugixml sfizz::spline sfizz::tunings sfizz::kissfft sfizz::cephes sfizz::cpuid sfizz::threadpool sfizz::jsl sfizz::atomic)
 if(SFIZZ_USE_SNDFILE)
     target_compile_definitions(sfizz_internal PUBLIC "SFIZZ_USE_SNDFILE=1")
     target_link_libraries(sfizz_internal PUBLIC st_audiofile)

src/sfizz/MathHelpers.h

@@ -296,6 +296,25 @@ constexpr long int lroundPositive(T value)
     return static_cast<int>(0.5f + value); // NOLINT
 }
 
+/**
+ * @brief Compute the next power of 2
+ *
+ * @param v An integer
+ * @return The next power of 2, inclusive from @p v
+ */
+inline uint32_t nextPow2(uint32_t v)
+{
+    // Bit Twiddling Hacks
+    v--;
+    v |= v >> 1;
+    v |= v >> 2;
+    v |= v >> 4;
+    v |= v >> 8;
+    v |= v >> 16;
+    v++;
+    return v;
+}
+
 /**
    @brief Wrap a normalized phase into the domain [0;1[
  */

src/sfizz/OversamplerHelpers.hxx

@@ -11,6 +11,7 @@
 
 #pragma once
 #include "OversamplerHelpers.h"
+#include "MathHelpers.h"
 
 namespace sfz {
 
@@ -94,6 +95,13 @@ public:
 			return factor * spl;
 		}
 	}
+	static unsigned conversionFactor(double sourceRate, double targetRate)
+	{
+		int factor = static_cast<int>(std::ceil(targetRate / sourceRate));
+		factor = (factor > 1) ? factor : 1;
+		factor = (factor < 128) ? factor : 128;
+		return nextPow2(factor);
+	}
 	static bool canProcess(int factor)
 	{
 		switch (factor) {
@@ -293,6 +301,13 @@ public:
 			return factor * spl;
 		}
 	}
+	static unsigned conversionFactor(double sourceRate, double targetRate)
+	{
+		int factor = static_cast<int>(std::ceil(targetRate / sourceRate));
+		factor = (factor > 1) ? factor : 1;
+		factor = (factor < 128) ? factor : 128;
+		return nextPow2(factor);
+	}
 	static bool canProcess(int factor)
 	{
 		switch (factor) {

tests/CMakeLists.txt

@@ -41,6 +41,7 @@ set(SFIZZ_TEST_SOURCES
     ModulationsT.cpp
     LFOT.cpp
     MessagingT.cpp
+    OversamplerT.cpp
     DataHelpers.h
     DataHelpers.cpp
 )

tests/OversamplerT.cpp

@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: BSD-2-Clause
+
+// This code is part of the sfizz library and is licensed under a BSD 2-clause
+// license. You should have receive a LICENSE.md file along with the code.
+// If not, contact the sfizz maintainers at https://github.com/sfztools/sfizz
+
+#include "sfizz/OversamplerHelpers.h"
+#include "catch2/catch.hpp"
+
+TEST_CASE("[Oversampler] Conversion factor")
+{
+    REQUIRE(sfz::Upsampler::conversionFactor(44100.0, 44100.0) == 1);
+    REQUIRE(sfz::Upsampler::conversionFactor(44100.0, 44101.0) == 2);
+    REQUIRE(sfz::Upsampler::conversionFactor(44100.0, 88200.0) == 2);
+    REQUIRE(sfz::Upsampler::conversionFactor(44100.0, 88201.0) == 4);
+    REQUIRE(sfz::Upsampler::conversionFactor(44100.0, 176400.0) == 4);
+    REQUIRE(sfz::Upsampler::conversionFactor(44100.0, 176401.0) == 8);
+    // low and high limits
+    REQUIRE(sfz::Upsampler::conversionFactor(44100.0, 1.0) == 1);
+    REQUIRE(sfz::Upsampler::conversionFactor(44100.0, 1e10) == 128);
+}