Inverse FFT corrections

Author: pschatzmann

src/AudioTools/AudioLibs/AudioFFT.h

@@ -91,6 +91,7 @@ class FFTInverseOverlapAdder {
 
   void resize(int size) {
     rfft_max = 0.0;
+    len = size;
     data.resize(size);
     for (int j = 0; j < data.size(); j++) {
       data[j] = 0.0;
@@ -240,6 +241,7 @@ class AudioFFTBase : public AudioStream {
     if (cfg.rxtx_mode == RX_MODE || cfg.rxtx_mode == RXTX_MODE) {
       rfft_data.resize(cfg.channels * bytesPerSample() * step_size);
       rfft_add.resize(cfg.length);
+      step_data.resize(cfg.stride);
       is_valid_rxtx = true;
     }
 
@@ -462,10 +464,10 @@ class AudioFFTBase : public AudioStream {
 
   // Add samples to input data p_x - and process them if full
   template <typename T>
-  void processSamples(const void *data, size_t samples) {
+  void processSamples(const void *data, size_t count) {
     T *dataT = (T *)data;
     T sample;
-    for (int j = 0; j < samples; j += cfg.channels) {
+    for (int j = 0; j < count; j += cfg.channels) {
       sample = dataT[j + cfg.channel_used];
       if (writeStrideBuffer((uint8_t *)&sample, sizeof(T))){
         // process data if buffer is full
@@ -527,10 +529,9 @@ class AudioFFTBase : public AudioStream {
   /// write reverse fft result to buffer to make it available for readBytes
   void rfftWriteData(BaseBuffer<uint8_t> &data) {
     // get data to result buffer
-    step_data.resize(cfg.stride);
-    for (int j = 0; j < cfg.stride; j++) {
-      step_data[j] = 0.0;
-    }
+    // for (int j = 0; j < cfg.stride; j++) {
+    //   step_data[j] = 0.0;
+    // }
     rfft_add.getStepData(step_data.data(), cfg.stride,
                          NumberConverter::maxValue(cfg.bits_per_sample));
 

src/AudioTools/AudioLibs/FFT/FFTWindows.h

@@ -75,7 +75,7 @@ class BufferedWindow : public WindowFunction {
     WindowFunction::begin(samples);
     if (p_wf->samples() != samples) {
       p_wf->begin(samples);
-      len = samples / 2;
+      len = samples;
       buffer.resize(len);
       for (int j = 0; j < len; j++) {
         buffer[j] = p_wf->factor(j);
@@ -89,7 +89,8 @@ class BufferedWindow : public WindowFunction {
   int len;
 
   float factor_internal(int idx) override {
-    return idx < len ? buffer[idx] : buffer[i_samples - idx];
+    if (idx < 0 || idx > len) return 0.0;
+    return buffer[idx];
   }
 };
 

tests-cmake/CMakeLists.txt

@@ -23,6 +23,7 @@ endif()
 add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/resample ${CMAKE_CURRENT_BINARY_DIR}/resample)
 add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/generator ${CMAKE_CURRENT_BINARY_DIR}/generator)
 add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/effects ${CMAKE_CURRENT_BINARY_DIR}/effects)
+add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/fft ${CMAKE_CURRENT_BINARY_DIR}/fft)
 add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/filter ${CMAKE_CURRENT_BINARY_DIR}/filter)
 add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/filter-wav ${CMAKE_CURRENT_BINARY_DIR}/filter-wav)
 add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/url-test ${CMAKE_CURRENT_BINARY_DIR}/url-test)

tests-cmake/fft/CMakeLists.txt

@@ -0,0 +1,35 @@
+cmake_minimum_required(VERSION 3.20)
+
+
+# set the project name
+project(fft)
+set (CMAKE_CXX_STANDARD 11)
+set (DCMAKE_CXX_FLAGS "-Werror")
+set (CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -O0 -ldl -lpthread -lm")
+set (CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -O0 -ldl -lpthread -lm")
+
+# Emulator is not necessary for -DIS_MIN_DESKTOP
+set(ADD_ARDUINO_EMULATOR OFF CACHE BOOL "Add Arduino Emulator Library") 
+set(ADD_PORTAUDIO OFF CACHE BOOL "No Portaudio") 
+
+# Build with arduino-audio-tools
+if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
+    add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/../.. ${CMAKE_CURRENT_BINARY_DIR}/arduino-audio-tools )
+endif()
+
+# Download miniaudio.h
+file(DOWNLOAD https://raw.githubusercontent.com/mackron/miniaudio/master/miniaudio.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/miniaudio.h)
+
+
+# build sketch as executable
+add_executable (fft fft.cpp)
+
+# set preprocessor defines
+target_compile_definitions(fft PUBLIC -DIS_MIN_DESKTOP)
+
+# specify libraries
+target_link_libraries(fft arduino-audio-tools)
+
+# access to miniaudio in sketch directory
+target_include_directories(fft PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})

tests-cmake/fft/fft.cpp

@@ -0,0 +1,48 @@
+#include "AudioTools.h"
+#include "AudioTools/AudioLibs/AudioRealFFT.h" // using RealFFT
+#include "AudioTools/AudioLibs/MiniAudioStream.h"
+
+AudioInfo info(44100, 2, 16);
+AudioRealFFT afft; // or AudioKissFFT
+Hann hann;
+BufferedWindow buffered(&hann);
+SineWaveGenerator<int16_t> sineWave(32000);
+GeneratedSoundStream<int16_t> in(sineWave);
+StreamCopy copier(afft, in);
+//CsvOutput<int16_t> out(Serial);
+MiniAudioStream out;
+StreamCopy copierIFFT(out, afft);
+
+// process fft result
+void fftResult(AudioFFTBase &fft) {
+  // copy ifft result to output
+  while (copierIFFT.copy());
+}
+
+void setup() {
+  AudioToolsLogger.begin(Serial, AudioToolsLogLevel::Warning);
+
+  // set the frequency
+  sineWave.setFrequency(N_B4);
+
+  // Setup sine wave
+  auto cfg = in.defaultConfig();
+  cfg.copyFrom(info);
+  in.begin(cfg);
+
+  // Setup FFT
+  auto tcfg = afft.defaultConfig(RXTX_MODE);
+  tcfg.copyFrom(info);
+  tcfg.length = 1024;
+  tcfg.window_function = &buffered;
+  tcfg.stride = 512;
+  tcfg.callback = fftResult;
+  afft.begin(tcfg);
+
+  // setup output
+  auto ocfg = out.defaultConfig(TX_MODE);
+  ocfg.copyFrom(info);
+  out.begin(ocfg);
+}
+
+void loop() { copier.copy(); }