analyze_fft1024_F32.cpp

/* analyze_fft1024_F32.cpp      Converted from Teensy I16 Audio Library
 * This version uses float F32 inputs.  See comments at analyze_fft1024_F32.h
 * Converted to use half-length FFT 17 March 2021  RSL
 *
 * Conversion parts copyright (c) Bob Larkin 2021
 *
 *  Audio Library for Teensy 3.X
 * Copyright (c) 2014, Paul Stoffregen, paul@pjrc.com
 *
 * Development of this audio library was funded by PJRC.COM, LLC by sales of
 * Teensy and Audio Adaptor boards.  Please support PJRC's efforts to develop
 * open source software by purchasing Teensy or other PJRC products.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice, development funding notice, and this permission
 * notice shall be included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include <Arduino.h>
#include "analyze_fft1024_F32.h"

// Move audio data from an audio_block_f32_t to the FFT instance buffer.
// This is for 128 numbers per block, only.
static void copy_to_fft_buffer(void *destination, const void *source)  {
    const float *src = (const float *)source;
    float *dst = (float *)destination;

    for (int i=0; i < 128; i++) {
        *dst++ = *src++;     // real sample for half-length FFT
        }
    }

static void apply_window_to_fft_buffer(void *buffer, const void *window) {
    float *buf = (float *)buffer;
    const float *win = (float *)window;

    for(int i=0; i<NFFT; i++)
       buf[i] *= *win++;
    }

void AudioAnalyzeFFT1024_F32::update(void)  {
    audio_block_f32_t *block;
    float outDC=0.0f;
    float magsq=0.0f;

    block = AudioStream_F32::receiveReadOnly_f32();
    if (!block) return;

    switch (state) {
    case 0:
        blocklist[0] = block;
        state = 1;
        break;
    case 1:
        blocklist[1] = block;
        state = 2;
        break;
    case 2:
        blocklist[2] = block;
        state = 3;
        break;
    case 3:
        blocklist[3] = block;
        state = 4;
        break;
    case 4:
        blocklist[4] = block;
        // Now the post FT processing for using half-length transform
        // FFT was in state==7, but it loops around to here.  Does some
        // zero data at startup that is harmless.
        count++;      // Next do non-coherent averaging
        for(int i=0; i<NFFT_D2; i++)  {
            if(i>0) {
               float rns = 0.5f*(fft_buffer[2*i] +   fft_buffer[NFFT-2*i]);
               float ins = 0.5f*(fft_buffer[2*i+1] + fft_buffer[NFFT-2*i+1]);
               float rnd = 0.5f*(fft_buffer[2*i] -   fft_buffer[NFFT-2*i]);
               float ind = 0.5f*(fft_buffer[2*i+1] - fft_buffer[NFFT-2*i+1]);

               float xr = rns + cosN[i]*ins - sinN[i]*rnd;
               float xi = ind - sinN[i]*ins - cosN[i]*rnd;
               magsq = xr*xr + xi*xi;
               }
            else  {
               magsq = outDC*outDC;    // Do the DC term
               }

            if(count==1)               // Starting new average
               sumsq[i] = magsq;
            else if (count<=nAverage)  // Adding on to average
               sumsq[i] += magsq;
            }

        if (count >= nAverage) {       // Average is finished
        // Set outputflag false here to minimize reads of output[]  data
        // when it is being updated.
        outputflag = false;
            count = 0;
            float inAf = 1.0f/(float)nAverage;
            float kMaxDB = 20.0*log10f((float)NFFT_D2);  // 54.1854 for 1024

            for(int i=0; i<NFFT_D2; i++)  {
               if(outputType==FFT_RMS)
                  output[i] = sqrtf(inAf*sumsq[i]);
               else if(outputType==FFT_POWER)
                  output[i] = inAf*sumsq[i];
               else if(outputType==FFT_DBFS)  {
                  if(sumsq[i]>0.0f)
                     output[i] = 10.0f*log10f(inAf*sumsq[i]) - kMaxDB;  // Scaled to FS sine wave
                  else
                     output[i] = -193.0f;   // lsb for 23 bit mantissa
                  }
               else
                  output[i] = 0.0f;
               }    // End, set output[i] over all NFFT_D2
            outputflag = true;
            }    // End of average is finished
        state = 5;
        break;
    case 5:
        blocklist[5] = block;
        state = 6;
        break;
    case 6:
        blocklist[6] = block;
        state = 7;
        break;
    case 7:
        blocklist[7] = block;
        // We have 4 previous blocks pointed to by blocklist[]:
        copy_to_fft_buffer(fft_buffer+0x000, blocklist[0]->data);
        copy_to_fft_buffer(fft_buffer+0x080, blocklist[1]->data);
        copy_to_fft_buffer(fft_buffer+0x100, blocklist[2]->data);
        copy_to_fft_buffer(fft_buffer+0x180, blocklist[3]->data);
        // and 4 new blocks, just gathered:
        copy_to_fft_buffer(fft_buffer+0x200, blocklist[4]->data);
        copy_to_fft_buffer(fft_buffer+0x280, blocklist[5]->data);
        copy_to_fft_buffer(fft_buffer+0x300, blocklist[6]->data);
        copy_to_fft_buffer(fft_buffer+0x380, blocklist[7]->data);

        if (pWin)
           apply_window_to_fft_buffer(fft_buffer, window);

        outDC = 0.0f;
        for(int i=0; i<NFFT; i++)
            outDC += fft_buffer[i];
        outDC /= ((float)NFFT);

#if defined(__IMXRT1062__)
        // Teensyduino core for T4.x supports arm_cfft_f32
        // arm_cfft_f32 (const arm_cfft_instance_f32 *S, float32_t *p1, uint8_t ifftFlag, uint8_t bitReverseFlag)
        arm_cfft_f32 (&Sfft, fft_buffer, 0, 1);
#else
        // For T3.x go back to old (deprecated) style (check radix2/radix4)<<<
        arm_cfft_radix2_f32(&fft_inst, fft_buffer);
#endif
        // FFT output is now in fft_buffer.  Pick up processing at state==4.

        AudioStream_F32::release(blocklist[0]);
        AudioStream_F32::release(blocklist[1]);
        AudioStream_F32::release(blocklist[2]);
        AudioStream_F32::release(blocklist[3]);

        blocklist[0] = blocklist[4];
        blocklist[1] = blocklist[5];
        blocklist[2] = blocklist[6];
        blocklist[3] = blocklist[7];
        state = 4;
        break;
     }     // End switch(state)
  }        // End update()