ESP32 Audio Board 2,2 404 Guitar Distortion pedal raw and distorted buffer play in real time and write to SDMMC

[AndreyLapshov]

Hello. Its a perfect library. I've got not bad sound. But if i try to write Wav to sdmmc while realtime process line in - effect - lineout i cant normally write, i have robotics playback. Is it possible to with esp-a1s to do two things at the same time. I just attach code of my audio processing here.
#include <Arduino.h>
#include <AudioTools.h>
#include <AudioTools/AudioLibs/AudioBoardStream.h>

// === Audio Constants ===
static constexpr int SAMPLE_RATE = 48000;
static constexpr int BITS_PER_SAMPLE = 16;
static constexpr int CHANNELS = 2;

// === Footswitch Pins ===
static constexpr int KEY_BYPASS = 36;
static constexpr int KEY_VOL_UP = 19;
static constexpr int KEY_VOL_DN = 23;
static constexpr int KEY_DRIVE_UP = 18;
static constexpr int KEY_DRIVE_DN = 5;

// === Globals ===
uint32_t lastPress[5] = {};
float masterVolume = 0.5f;

// === Audio Streams ===
AudioBoardStream board(AudioKitEs8388V1);
AudioEffectStream fx(board);
StreamCopy copier(board, fx);

// === DSP Classes ===
class Biquad {
float b0=0,b1=0,b2=0,a1=0,a2=0;
float x1=0,x2=0,y1=0,y2=0;
public:
void setHighpass(float f0,float fs,float Q=0.707f){
float w0=2PIf0/fs,cosw=cosf(w0),sinw=sinf(w0),alpha=sinw/(2Q);
float b0u=(1+cosw)/2,b1u=-(1+cosw),b2u=b0u;
float a0u=1+alpha,a1u=-2cosw,a2u=1-alpha;
b0=b0u/a0u; b1=b1u/a0u; b2=b2u/a0u;
a1=a1u/a0u; a2=a2u/a0u;
x1=x2=y1=y2=0;
}
void setLowpass(float f0,float fs,float Q=0.707f){
float w0=2PIf0/fs,cosw=cosf(w0),sinw=sinf(w0),alpha=sinw/(2Q);
float b0u=(1-cosw)/2,b1u=1-cosw,b2u=b0u;
float a0u=1+alpha,a1u=-2cosw,a2u=1-alpha;
b0=b0u/a0u; b1=b1u/a0u; b2=b2u/a0u;
a1=a1u/a0u; a2=a2u/a0u;
x1=x2=y1=y2=0;
}
void setPeaking(float f0,float fs,float Q,float gainDB){
float A=powf(10.0f,gainDB/40.0f);
float w0=2PIf0/fs,cosw=cosf(w0),sinw=sinf(w0),alpha=sinw/(2Q);
float b0u=1+alphaA,b1u=-2cosw,b2u=1-alphaA;
float a0u=1+alpha/A,a1u=-2cosw,a2u=1-alpha/A;
b0=b0u/a0u; b1=b1u/a0u; b2=b2u/a0u;
a1=a1u/a0u; a2=a2u/a0u;
x1=x2=y1=y2=0;
}
float process(float x){
float y=b0x + b1x1 + b2x2 - a1y1 - a2y2;
x2=x1; x1=x; y2=y1; y1=y;
return y;
}
};

class MyCompressor {
float thr,invR;
public:
MyCompressor(float t=0.6f,float r=6.0f):thr(t),invR(1.0f/r){}
float process(float x)const{
float a=fabsf(x);
if(a<=thr) return x;
float exc=a-thr,cmp=thr+exc*invR;
return copysignf(cmp,x);
}
};

class MeatDist : public AudioEffect {
Biquad preHP1, preHP2, postLP1, postLP2, midCut;
MyCompressor comp{0.5f,8.0f};
float drive=8.0f, bias=0.15f, sustain=0.0f, yPrev=0.0f;
float makeupGain=1.2f, mix=1.0f, lastIn=0.0f;
public:
MeatDist(){
preHP1.setHighpass(80,SAMPLE_RATE);
preHP2.setHighpass(80,SAMPLE_RATE);
postLP1.setLowpass(6000,SAMPLE_RATE);
postLP2.setLowpass(6000,SAMPLE_RATE);
midCut.setPeaking(800,SAMPLE_RATE,0.7f,-8.0f);
}
AudioEffect* clone() override { return new MeatDist(this); }
void setActive(bool a){ AudioEffect::setActive(a); yPrev=0; lastIn=0; }
void setDrive(float v){ drive=constrain(v,1.0f,30.0f); }
float getDrive() const { return drive; }
void setPresence(float f){ preHP2.setHighpass(f,SAMPLE_RATE); }
void setTone(float f){ postLP2.setLowpass(f,SAMPLE_RATE); }
void setMakeup(float v){ makeupGain=constrain(v,0.1f,10.0f); }
void setMidCutGain(float g){ midCut.setPeaking(800,SAMPLE_RATE,0.7f,g); }
void setSustain(float v){ sustain=constrain(v,0.0f,0.99f); }
effect_t process(effect_t in) override {
if(!active()) return in;
float x_in = in/32768.0f, y_out;
float x_mid = (lastIn + x_in)0.5f;
processSample(x_mid);
y_out = processSample(x_in);
lastIn = x_in;
long s = lroundf(y_out32767.0f);
return (effect_t)constrain(s,-32768,32767);
}
private:
float processSample(float x){
x = preHP1.process(x);
x = preHP2.process(x);
float t = (x + bias)drive; t = constrain(t,-1.0f,1.0f);
float y = t - ttt/3.0f;
float tb = biasdrive; tb = constrain(tb,-1.0f,1.0f);
float by = tb - tbtbtb/3.0f;
x = y - by;
x = comp.process(x);
x = x + sustainyPrev; yPrev = x;
x = postLP1.process(x);
x = midCut.process(x);
x = postLP2.process(x);
x = makeupGain;
float dry = lastIn;
return mixx + (1-mix)*dry;
}
};

MeatDist dist;

// debounce
bool checkKey(int pin,int idx){
if(digitalRead(pin)==LOW && millis()-lastPress[idx]>200){
lastPress[idx]=millis();
return true;
}
return false;
}

// single audio task for I²S in→FX→DAC
void audioTask(void*) {
while(true){
copier.copy();
vTaskDelay(pdMS_TO_TICKS(1));
}
}

void setup(){
Serial.begin(115200);
pinMode(KEY_BYPASS, INPUT);
for(int pin:{KEY_VOL_UP,KEY_VOL_DN,KEY_DRIVE_UP,KEY_DRIVE_DN})
pinMode(pin, INPUT_PULLUP);

auto cfg = board.defaultConfig(RXTX_MODE);
cfg.sample_rate = SAMPLE_RATE;
cfg.bits_per_sample = BITS_PER_SAMPLE;
cfg.channels = CHANNELS;
cfg.input_device = ADC_INPUT_LINE2;
cfg.buffer_size = 4096;
cfg.buffer_count = 16;
//cfg.sd_active = false;
board.begin(cfg);
board.setVolume(masterVolume);

fx.addEffect(&dist);
fx.begin(cfg);

xTaskCreatePinnedToCore(
audioTask, "audio", 4096, nullptr, 3, nullptr, 0
);
}

void loop(){
if(checkKey(KEY_VOL_UP,1)){
masterVolume = min(masterVolume+0.1f,1.0f);
board.setVolume(masterVolume);
Serial.printf("Volume=%.1f\n", masterVolume);
}
if(checkKey(KEY_VOL_DN,2)){
masterVolume = max(masterVolume-0.1f,0.0f);
board.setVolume(masterVolume);
Serial.printf("Volume=%.1f\n", masterVolume);
}
if(checkKey(KEY_DRIVE_UP,3)){
dist.setDrive(dist.getDrive()+1);
Serial.printf("Drive=%.1f\n", dist.getDrive());
}
if(checkKey(KEY_DRIVE_DN,4)){
dist.setDrive(dist.getDrive()-1);
Serial.printf("Drive=%.1f\n", dist.getDrive());
}

if(checkKey(KEY_BYPASS,0)){
bool a = !dist.active();
dist.setActive(a);
Serial.printf("Effect %s\n", a ? "ON" : "OFF");
}

// serial params (P,T,M,D,C,S) as before...
if(Serial.available()){
String s = Serial.readStringUntil('\n');
if(s.startsWith("P")){ float f=s.substring(1).toFloat(); dist.setPresence(f); Serial.printf("HPF=%.0fHz\n",f); }
if(s.startsWith("T")){ float f=s.substring(1).toFloat(); dist.setTone(f); Serial.printf("LPF=%.0fHz\n",f); }
if(s.startsWith("M")){ float g=s.substring(1).toFloat(); dist.setMakeup(g); Serial.printf("Makeup=%.2f\n",g); }
if(s.startsWith("D")){ float d=s.substring(1).toFloat(); dist.setDrive(d); Serial.printf("Drive=%.1f\n",dist.getDrive()); }
if(s.startsWith("C")){ float db=s.substring(1).toFloat(); dist.setMidCutGain(db); Serial.printf("MidCut=%.1fdB\n",db); }
if(s.startsWith("S")){ float sv=s.substring(1).toFloat(); dist.setSustain(sv); Serial.printf("Sustain=%.2f\n",sv); }
}

delay(10);
}
Also a have to ask may be you or anyone knows better drive distortion effect for guitar with good sustain and attack even like guitarpro sound or cheap digital guitar processor?

[pschatzmann]

I am not sure if I understand your question: if you want to write out the audio to the SD, you will need to make sure that write thruput is not lower than the the one required to process the audio: a first step would be to lower the sample rate and if you have determined the acutal working rate you can try to improve the write speed.

If you just want to do some SD processing in parallel, you would use a separate task.

Here is the list of all available effects.