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spectral: Add Spectral noise reduction

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Add Spectral Noise Reduction module, based on the code from
the UHSDR / Convolution-SDR code bases.

Signed-off-by: Graham Whaley <graham.whaley@gmail.com>
pull/13/head
Graham Whaley 3 years ago
parent a609fa8602
commit 065689a892
3 changed files with 541 additions and 0 deletions
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  1. 342
      AudioSpectralDenoise_F32.cpp
  2. 198
      AudioSpectralDenoise_F32.h
  3. 1
      OpenAudio_ArduinoLibrary.h

342
AudioSpectralDenoise_F32.cpp
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/* AudioSpectralDenoise_F2.h
* Spectral noise reduction
*
* Extracted and based on the work found in the:
* - Convolution SDR: https://github.com/DD4WH/Teensy-ConvolutionSDR
* - UHSDR: https://github.com/df8oe/UHSDR/blob/active-devel/mchf-eclipse/drivers/audio/audio_nr.c
*
* License: GNU GPLv3
* Both the Convolution SDR and UHSDR are licensed under GPLv3.
*/
#include "AudioSpectralDenoise_F32.h"
#include <new>
// No serial debug by default
static const bool serial_debug = false;
int AudioSpectralDenoise_F32::setup(const AudioSettings_F32 & settings,
const int _N_FFT)
{
enable(false); //Disable us, just incase we are already active...
sample_rate_Hz = settings.sample_rate_Hz;
if (N_FFT == -1) {
//setup the FFT and IFFT. If they return a negative FFT, it wasn't an allowed FFT size.
N_FFT = myFFT.setup(settings, _N_FFT); //hopefully, we got the same N_FFT that we asked for
if (N_FFT < 1)
return N_FFT;
N_FFT = myIFFT.setup(settings, _N_FFT); //hopefully, we got the same N_FFT that we asked for
if (N_FFT < 1)
return N_FFT;
//As we do a complex fft on a real signal, we only use half the returned FFT bins due
// to conjugate symmetry. Store the number of bins to make it obvious and handy.
N_bins = N_FFT / 2;
//Spectral uses sqrtHann filtering
(myFFT.getFFTObject())->useHanningWindow(); //applied prior to FFT
//allocate memory to hold frequency domain data - complex r+i, so double the size of the
// fft size.
complex_2N_buffer = new (std::nothrow) float32_t[2 * N_FFT];
if (complex_2N_buffer == NULL) return -1;
NR_X = new (std::nothrow) float32_t[N_bins];
if (NR_X == NULL) return -1;
ph1y = new (std::nothrow) float32_t[N_bins];
if (ph1y == NULL) return -1;
pslp = new (std::nothrow) float32_t[N_bins];
if (pslp == NULL) return -1;
xt = new (std::nothrow) float32_t[N_bins];
if (xt == NULL) return -1;
NR_SNR_post = new (std::nothrow) float32_t[N_bins];
if (NR_SNR_post == NULL) return -1;
NR_SNR_prio = new (std::nothrow) float32_t[N_bins];
if (NR_SNR_prio == NULL) return -1;
NR_Hk_old = new (std::nothrow) float32_t[N_bins];
if (NR_Hk_old == NULL) return -1;
NR_G = new (std::nothrow) float32_t[N_bins];
if (NR_G == NULL) return -1;
NR_Nest = new (std::nothrow) float32_t[N_bins];
if (NR_Nest == NULL) return -1;
}
//Clear out and initialise
for (int bindx = 0; bindx < N_bins; bindx++) {
NR_Hk_old[bindx] = 0.1; // old gain
NR_Nest[bindx] = 0.01;
NR_X[bindx] = 0.0;
NR_SNR_post[bindx] = 2.0;
NR_SNR_prio[bindx] = 1.0;
NR_G[bindx] = 0.0;
}
//Work out the 'bin' range for our chosen voice frequencies
// divide 2 to account for nyquist
VAD_low = VAD_low_freq / ((sample_rate_Hz / 2.0) / (float32_t) (N_bins));
VAD_high = VAD_high_freq / ((sample_rate_Hz / 2.0) / (float32_t) N_bins);
xih1 = powf(10, asnr / 10.0);
pfac = (1.0 / pspri - 1.0) * (1.0 + xih1);
xih1r = 1.0 / (1.0 + xih1) - 1.0;
//Configure the other things that might rely on the fft size of bitrate
tinc = 1.0 / (sample_rate_Hz / AUDIO_BLOCK_SAMPLES); //Frame time
tax = -tinc / log(tax_factor); //noise output smoothing constant in seconds = -tinc/ln(0.8)
tap = -tinc / log(tap_factor); //speech prob smoothing constant in seconds = -tinc/ln(0.9)
ap = expf(-tinc / tap); //noise output smoothing factor
ax = expf(-tinc / tax); //noise output smoothing factor
if (serial_debug) {
Serial.println(" Spectral setup with fft:" + String(N_FFT));
Serial.println(" FFT nblocks:" + String(myFFT.getNBuffBlocks()));
Serial.println(" iFFT nblocks:" + String(myIFFT.getNBuffBlocks()));
Serial.println(" Sample rate:" + String(sample_rate_Hz));
Serial.println(" bins:" + String(N_bins));
Serial.println(" VAD low:" + String(VAD_low));
Serial.println(" VAD low freq:" + String(getVADLowFreq()));
Serial.println(" VAD high:" + String(VAD_high));
Serial.println(" VAD high freq:" + String(getVADHighFreq()));
Serial.println(" tinc:" + String(tinc, 5));
Serial.println(" tax_factor:" + String(tax_factor, 5));
Serial.println(" tap_factor:" + String(tap_factor, 5));
Serial.println(" tax:" + String(tax, 5));
Serial.println(" tap:" + String(tap, 5));
Serial.println(" ax:" + String(ax, 5));
Serial.println(" ap:" + String(ap, 5));
Serial.println(" xih1:" + String(xih1, 5));
Serial.println(" xih1r:" + String(xih1r, 5));
Serial.println(" pfac:" + String(pfac, 5));
Serial.println(" snr_prio_min:" + String(getSNRPrioMin(), 5));
Serial.println(" power_threshold:" + String(getPowerThreshold(), 5));
Serial.println(" asnr:" + String(getAsnr(), 5));
Serial.println(" NR_alpha:" + String(getNRAlpha(), 5));
Serial.println(" NR_width:" + String(getNRWidth(), 5));
Serial.flush();
}
enable(true);
return is_enabled;
}
void AudioSpectralDenoise_F32::update(void)
{
//get a pointer to the latest data
audio_block_f32_t *in_audio_block = AudioStream_F32::receiveReadOnly_f32();
if (!in_audio_block)
return;
//simply return the audio if this class hasn't been enabled
if (!is_enabled) {
AudioStream_F32::transmit(in_audio_block);
AudioStream_F32::release(in_audio_block);
return;
}
//******************************************************************************
//convert to frequency domain
//FFT is in complex_2N_buffer, interleaved real, imaginary, real, imaginary, etc
myFFT.execute(in_audio_block, complex_2N_buffer);
// Preserve the block id, so we can pass it out with our final result
unsigned long incoming_id = in_audio_block->id;
// We just passed ownership of in_audio_block to myFFT, so we can
// release it here as we won't use it here again.
AudioStream_F32::release(in_audio_block);
if (init_phase == 1) {
if (serial_debug) {
Serial.println("One time init");
Serial.flush();
}
init_phase++;
for (int bindx = 0; bindx < N_bins; bindx++) {
NR_G[bindx] = 1.0;
NR_Hk_old[bindx] = 1.0; // old gain or xu in development mode
NR_Nest[bindx] = 0.0;
pslp[bindx] = 0.5;
}
}
//******************************************************************************
//***** Calculate magnitude, used later for noise estimates and calculations
// AIUI, as we are only passing real values into a complex FFT, the resulting
// data contains duplicated mirrored data, thus we only need to evaluate the
// magnitude of the first half of the bins, as it will be identical to that
// of the second half of the bins. When we finally apply the NR results to the
// FFT data we apply it to both the first half and the conjugate, mirror style.
// Fundamentally, this saves us half the processing on some parts.
for (int bindx = 0; bindx < N_bins; bindx++) {
NR_X[bindx] =
(complex_2N_buffer[bindx * 2] * complex_2N_buffer[bindx * 2] +
complex_2N_buffer[bindx * 2 + 1] * complex_2N_buffer[bindx * 2 + 1]);
}
//Second stage initialisation
if (init_phase == 2) {
static int NR_init_counter = 0;
if (serial_debug) {
Serial.println("Two time init (" + String(NR_init_counter) + ")");
Serial.flush();
}
for (int bindx = 0; bindx < N_bins; bindx++) {
// we do it 20 times to average over 20 frames for app. 100ms only on
// NR_on/bandswitch/modeswitch,...
NR_Nest[bindx] = NR_Nest[bindx] + 0.05 * NR_X[bindx];
xt[bindx] = psini * NR_Nest[bindx];
}
NR_init_counter++;
if (NR_init_counter > 19) //average over 20 frames for app. 100ms
{
if (serial_debug) {
Serial.println("Two time init done");
Serial.flush();
}
NR_init_counter = 0;
init_phase++;
}
if (serial_debug)
Serial.println(" Two time loop done");
}
//Now we are fully initialised, we can actually do the NR processing
//******************************************************************************
//MMSE (Minimum Mean Square Error) based noise estimate
// code/algo inspired by the matlab based voicebox library:
// http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
// Noise estimate code can be found at:
// https://github.com/YouriT/matlab-speech/blob/master/MATLAB_CODE_SOURCE/voicebox/estnoiseg.m
for (int bindx = 0; bindx < N_bins; bindx++) {
float32_t xtr;
// a-posteriori speech presence probability
ph1y[bindx] = 1.0 / (1.0 + pfac * expf(xih1r * NR_X[bindx] / xt[bindx]));
// smoothed speech presence probability
pslp[bindx] = ap * pslp[bindx] + (1.0 - ap) * ph1y[bindx];
// limit ph1y
if (pslp[bindx] > psthr) {
ph1y[bindx] = 1.0 - pnsaf;
} else {
ph1y[bindx] = fmin(ph1y[bindx], 1.0);
}
// estimated raw noise spectrum
xtr = (1.0 - ph1y[bindx]) * NR_X[bindx] + ph1y[bindx] * xt[bindx];
// smooth the noise estimate
xt[bindx] = ax * xt[bindx] + (1.0 - ax) * xtr;
}
// Limit the ratios
// I don't have a lot of info on how this works, but SNRpost and SNRprio are related
// to both Ephraim&Malah(84) and Romanin(2009) papers
for (int bindx = 0; bindx < N_bins; bindx++) {
// limited to +30 /-15 dB, might be still too much of reduction, let's try it?
NR_SNR_post[bindx] = fmax(fmin(NR_X[bindx] / xt[bindx], 1000.0), snr_prio_min);
NR_SNR_prio[bindx] =
fmax(NR_alpha * NR_Hk_old[bindx] +
(1.0 - NR_alpha) * fmax(NR_SNR_post[bindx] - 1.0, 0.0), 0.0);
}
//******************************************************************************
// VAD
// maybe we should limit this to the signal containing bins (filtering!!)
for (int bindx = VAD_low; bindx < VAD_high; bindx++) {
float32_t v =
NR_SNR_prio[bindx] * NR_SNR_post[bindx] / (1.0 + NR_SNR_prio[bindx]);
NR_G[bindx] = 1.0 / NR_SNR_post[bindx] * sqrtf((0.7212 * v + v * v));
NR_Hk_old[bindx] = NR_SNR_post[bindx] * NR_G[bindx] * NR_G[bindx];
}
//******************************************************************************
// Do the musical noise reduction
// musical noise "artefact" reduction by dynamic averaging - depending on SNR ratio
pre_power = 0.0;
post_power = 0.0;
for (int bindx = VAD_low; bindx < VAD_high; bindx++) {
pre_power += NR_X[bindx];
post_power += NR_G[bindx] * NR_G[bindx] * NR_X[bindx];
}
power_ratio = post_power / pre_power;
if (power_ratio > power_threshold) {
power_ratio = 1.0;
NN = 1;
} else {
NN = 1 + 2 * (int)(0.5 +
NR_width * (1.0 - power_ratio / power_threshold));
}
for (int bindx = VAD_low + NN / 2; bindx < VAD_high - NN / 2; bindx++) {
NR_Nest[bindx] = 0.0;
for (int m = bindx - NN / 2; m <= bindx + NN / 2; m++) {
NR_Nest[bindx] += NR_G[m];
}
NR_Nest[bindx] /= (float32_t) NN;
}
// and now the edges - only going NN steps forward and taking the average
// lower edge
for (int bindx = VAD_low; bindx < VAD_low + NN / 2; bindx++) {
NR_Nest[bindx] = 0.0;
for (int m = bindx; m < (bindx + NN); m++) {
NR_Nest[bindx] += NR_G[m];
}
NR_Nest[bindx] /= (float32_t) NN;
}
// upper edge - only going NN steps backward and taking the average
for (int bindx = VAD_high - NN; bindx < VAD_high; bindx++) {
NR_Nest[bindx] = 0.0;
for (int m = bindx; m > (bindx - NN); m--) {
NR_Nest[bindx] += NR_G[m];
}
NR_Nest[bindx] /= (float32_t) NN;
}
// end of edge treatment
for (int bindx = VAD_low + NN / 2; bindx < VAD_high - NN / 2; bindx++) {
NR_G[bindx] = NR_Nest[bindx];
}
// end of musical noise reduction
//******************************************************************************
// And finally actually apply the weightings to the signals...
// FINAL SPECTRAL WEIGHTING: Multiply current FFT results with complex_2N_buffer for
// bins with the bin-specific gain factors G
for (int bindx = 0; bindx < N_bins; bindx++) {
// real part
complex_2N_buffer[bindx * 2] = complex_2N_buffer[bindx * 2] * NR_G[bindx];
// imag part
complex_2N_buffer[bindx * 2 + 1] =
complex_2N_buffer[bindx * 2 + 1] * NR_G[bindx];
// real part conjugate symmetric
//N_bins * 4 == N_FFT * 2 == N_FFT[real, imag]
complex_2N_buffer[N_bins * 4 - bindx * 2 - 2] =
complex_2N_buffer[N_bins * 4 - bindx * 2 - 2] * NR_G[bindx];
// imag part conjugate symmetric
complex_2N_buffer[N_bins * 4 - bindx * 2 - 1] =
complex_2N_buffer[N_bins * 4 - bindx * 2 - 1] * NR_G[bindx];
}
//******************************************************************************
//And finally call the IFFT, back to the time domain, and pass the processed block on
//out_block is pre-allocated in here.
audio_block_f32_t *out_audio_block = myIFFT.execute(complex_2N_buffer);
//update the block number to match the incoming one
out_audio_block->id = incoming_id;
//send the returned audio block. Don't issue the release command here because myIFFT will re-use it
//don't release this buffer because myIFFT re-uses it within its own code
AudioStream_F32::transmit(out_audio_block); //don't release this buffer because myIFFT re-uses it within its own code
return;
}

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AudioSpectralDenoise_F32.h
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/*
* AudioSpectralDenoise_F32
*
* Created: Graham Whaley, 2022
* Purpose: Spectral noise reduction
*
* This processes a single stream of audio data (i.e., it is mono)
*
* License: GNU GPLv3 License
* As the code it is derived from is GPLv3
*
* Based off the work from the UHSDR project, as also used in the mcHF and Convolution-SDR
* projects.
* Reference documentation can be found at https://github.com/df8oe/UHSDR/wiki/Noise-reduction
* Code extracted into isolated files can be found at
* https://github.com/grahamwhaley/DSPham/blob/master/spectral.cpp
*/
#ifndef _AudioSpectralDenoise_F32_h
#define _AudioSpectralDenoise_F32_h
#include "AudioStream_F32.h"
#include <arm_math.h>
#include "FFT_Overlapped_OA_F32.h"
#include <Arduino.h>
class AudioSpectralDenoise_F32:public AudioStream_F32 {
//GUI: inputs:1, outputs:1 //this line used for automatic generation of GUI node
//GUI: shortName:spectral
public:
AudioSpectralDenoise_F32(void):AudioStream_F32(1, inputQueueArray_f32) {
};
AudioSpectralDenoise_F32(const AudioSettings_F32 &
settings):AudioStream_F32(1, inputQueueArray_f32) {
}
AudioSpectralDenoise_F32(const AudioSettings_F32 & settings,
const int _N_FFT):AudioStream_F32(1,
inputQueueArray_f32)
{
setup(settings, _N_FFT);
}
//destructor...release all of the memory that has been allocated
~AudioSpectralDenoise_F32(void) {
if (complex_2N_buffer) delete complex_2N_buffer;
if (NR_X) delete NR_X;
if (ph1y) delete ph1y;
if (pslp) delete pslp;
if (xt) delete xt;
if (NR_SNR_post) delete NR_SNR_post;
if (NR_SNR_prio) delete NR_SNR_prio;
if (NR_Hk_old) delete NR_Hk_old;
if (NR_G) delete NR_G;
if (NR_Nest) delete NR_Nest;
}
//Our default FFT size is 256. That is time and space efficient, but
// if you are running at a 'high' sample rate, the NR 'buckets' might
// be quite small. You may want to use a 1024 FFT if running at 44.1KHz
// for instance, if you can afford the time and space overheads.
int setup(const AudioSettings_F32 & settings, const int _N_FFT = 256);
virtual void update(void);
bool enable(bool state = true) {
is_enabled = state;
return is_enabled;
}
bool enabled(void) {
return is_enabled;
}
//Getters and Setters
float32_t getAsnr(void) {
return asnr;
}
void setAsnr(float32_t v) {
asnr = v;
}
float32_t getVADHighFreq(void) {
return VAD_high_freq;
}
void setVADHighFreq(float32_t f) {
VAD_high_freq = f;
}
float32_t getVADLowFreq(void) {
return VAD_low_freq;
}
void setVADLowFreq(float32_t f) {
VAD_low_freq = f;
}
float32_t getNRAlpha(void) {
return NR_alpha;
}
void setNRAlpha(float32_t v) {
NR_alpha = v;
if (NR_alpha < 0.9)
NR_alpha = 0.9;
if (NR_alpha > 0.9999)
NR_alpha = 0.9999;
}
float32_t getSNRPrioMin(void) {
return snr_prio_min;
}
void setSNRPrioMin(float32_t v) {
snr_prio_min = v;
}
int16_t getNRWidth(void) {
return NR_width;
}
void setNRWidth(int16_t v) {
NR_width = v;
}
float32_t getPowerThreshold(void) {
return power_threshold;
}
void setPowerThreshold(float32_t v) {
power_threshold = v;
}
float32_t getTaxFactor(void) {
return tax_factor;
}
void setTaxFactor(float32_t v) {
tax_factor = v;
}
float32_t getTapFactor(void) {
return tap_factor;
}
void setTapFactor(float32_t v) {
tap_factor = v;
}
private:
static const int max_fft = 2048; //The largest FFT FFT_OA handles. Fixed so we can fix the
//array sizes - FIXME - a hack, but easier than doing the dynamic allocations for now.
uint8_t init_phase = 1; //Track our phases of initialisation
int is_enabled = 0;
float32_t *complex_2N_buffer; //Store our FFT real/imag data
audio_block_f32_t *inputQueueArray_f32[1]; //memory pointer for the input to this module
FFT_Overlapped_OA_F32 myFFT;
IFFT_Overlapped_OA_F32 myIFFT;
int N_FFT = -1; //How big an FFT are we using?
int N_bins = -1; //How many actual data bins are we processing on
float sample_rate_Hz = AUDIO_SAMPLE_RATE;
//*********** NR vars
//Magnitudes (fabs) of power for the last four (three?) audio blocks
float32_t *NR_X = NULL;
float32_t *ph1y = NULL;
float32_t *pslp = NULL;
float32_t *xt = NULL;
const float32_t psini = 0.5; //initial speech probability
const float32_t pspri = 0.5; //prior speech probability
float32_t asnr = 25; //active SNR in dB - seems to make less different than I expected.
float32_t xih1;
float32_t pfac;
float32_t xih1r;
const float32_t psthr = 0.99; //threshold for smoothed speech probability
const float32_t pnsaf = 0.01; //noise probability safety value
float32_t tinc; //Frame time in seconds
float32_t tax_factor = 0.8; //Noise output smoothing factor
float32_t tax; //noise output smoothing constant in seconds = -tinc/ln(0.8)
float32_t tap_factor = 0.9; //Speech probability smoothing factor
float32_t tap; //speech prob smoothing constant in seconds = -tinc/ln(0.9)
float32_t ap; //noise output smoothing factor
float32_t ax; //noise output smoothing factor
float32_t snr_prio_min = powf(10, -(float32_t) 20 / 20.0); //Lower limit of SNR ratio calculation
// Time smoothing of gain weights. Makes quite a difference to the NR performance.
float32_t NR_alpha = 0.99; //range 0.98-0.9999. 0.95 acts much too hard: reverb effects.
float32_t *NR_SNR_post = NULL;
float32_t *NR_SNR_prio = NULL;
float32_t *NR_Hk_old = NULL;
// preliminary gain factors (before time smoothing) and after that contains the frequency
// smoothed gain factors
float32_t *NR_G = NULL;
//Our Noise estimate array - 'one dimentional' is a hangover from the old version of the
// original code that used multiple entries for averaging, which seems to have then been
// dropped, but the arrays still left in place.
float32_t *NR_Nest = NULL;
float32_t VAD_low_freq = 100.0;
float32_t VAD_high_freq = 3600.0;
//if we grow the FFT to 1024, these might need to be bigger than a uint8?
uint8_t VAD_low, VAD_high; //lower/upper bounds for 'voice spectrum' slot processing
int16_t NN; //used as part of VAD calculations, n-bin averaging?. Also, why an int16 ?
int16_t NR_width = 4;
float32_t pre_power, post_power; //Used in VAD calculations
float32_t power_ratio;
float32_t power_threshold = 0.4;
};
#endif

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OpenAudio_ArduinoLibrary.h
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@ -21,6 +21,7 @@
#include "AudioMixer_F32.h" #include "AudioMixer_F32.h"
#include "AudioMultiply_F32.h" #include "AudioMultiply_F32.h"
#include "AudioSettings_F32.h" #include "AudioSettings_F32.h"
#include "AudioSpectralDenoise_F32.h"
#include "input_i2s_f32.h" #include "input_i2s_f32.h"
#include "output_i2s_f32.h" #include "output_i2s_f32.h"
#include "play_queue_f32.h" #include "play_queue_f32.h"

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