Audio record to SD sounds garbled

[donperryjm]

Hello, I'm recording audio using the example code below. T4.1
The output has however been garbled.

In passthrough mode the audio comes over cleanly to the USB. No issues there.
Issue arises when trying to record to the stereo raw file to SD card.

I've also attached the source audio file and the recorded garbled file. (I'm playing the source file to the input and using the teensy to record it to compare quality/clarity)

#include <Audio.h>
#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <SerialFlash.h>
 
// GUItool: begin automatically generated code
AudioInputI2S            is2stereoIn;    //xy=127.19999694824219,332
AudioAmplifier           amp1L;          //xy=372.1999969482422,177
AudioAmplifier           amp1R;          //xy=425.1999969482422,490
AudioFilterBiquad        biquad1L;       //xy=638.1999969482422,186
AudioFilterBiquad        biquad1R;       //xy=661.1999969482422,539
AudioAnalyzePeak         peakL;          //xy=810.1999969482422,136
AudioOutputUSB           usb2;           //xy=826.1999969482422,331
AudioAnalyzePeak         peakR;          //xy=839.1999969482422,626
AudioRecordQueue         queue1;         //xy=851.1999969482422,208.1999969482422
AudioRecordQueue         queue2;         //xy=888.1999969482422,523.1999969482422
AudioConnection          patchCord1(is2stereoIn, 0, amp1L, 0);
AudioConnection          patchCord2(is2stereoIn, 1, amp1R, 0);
AudioConnection          patchCord3(amp1L, biquad1L);
AudioConnection          patchCord4(amp1R, biquad1R);
AudioConnection          patchCord5(biquad1L, peakL);
AudioConnection          patchCord6(biquad1L, 0, usb2, 0);
AudioConnection          patchCord7(biquad1L, queue1);
AudioConnection          patchCord8(biquad1R, peakR);
AudioConnection          patchCord9(biquad1R, 0, usb2, 1);
AudioConnection          patchCord10(biquad1R, queue2);
// GUItool: end automatically generated code

 

// which input on the audio shield will be used?
const int myInput = AUDIO_INPUT_LINEIN;
//const int myInput = AUDIO_INPUT_MIC;


// Use these with the Teensy Audio Shield
#define SDCARD_CS_PIN    BUILTIN_SDCARD
#define SDCARD_MOSI_PIN  7
#define SDCARD_SCK_PIN   14

 
// Remember which mode we're doing
int mode = 0;  // 0=stopped, 1=recording, 2=playing



// The file where data is recorded
File frec;

void setup() {
  // record queue uses this memory to buffer incoming audio.
  AudioMemory(120); // 60
 


  // Initialize the SD card
  SPI.setMOSI(SDCARD_MOSI_PIN);
  SPI.setSCK(SDCARD_SCK_PIN);
  if (!(SD.begin(SDCARD_CS_PIN))) {
    // stop here if no SD card, but print a message
    while (1) {
      Serial.println("Unable to access the SD card");
      delay(500);
    }
  }

amp1L.gain(1);   
  amp1R.gain(1);   
   
 
  biquad1L.setHighpass(0, 200, 1.0); //1.5 was 2.0
  biquad1L.setLowpass(1, 10000, 1.0); //1.5 was 2.0
  biquad1R.setHighpass(0, 200, 1.0); //1.5 was 2.0
  biquad1R.setLowpass(1, 10000, 1.0); //1.5 was 2.0



  startRecording();
}


void loop() {
  if (millis() > 10000 && mode == 1) {
    stopRecording();
  }
  else {
    if (mode == 1) continueRecording();
  }
}

void startRecording() {
  Serial.println("StartRecording");
  if (SD.exists("RECORD.RAW")) {
    SD.remove("RECORD.RAW");
  }
  frec = SD.open("RECORD.RAW", FILE_WRITE);
  if (frec) {
    Serial.println("File Open");
    queue1.begin();
    queue2.begin();
    mode = 1;
  }

}

// write all 512 bytes to the SD card   
void continueRecording() {
  if (queue1.available() >= 2 && queue2.available() >= 2) {
    byte buffer[512];
    byte bufferL[256];
    byte bufferR[256];
    memcpy(bufferL, queue1.readBuffer(), 256);
    memcpy(bufferR, queue2.readBuffer(), 256);
    queue1.freeBuffer();
    queue2.freeBuffer();
    int b = 0;
    for (int i = 0; i < 512; i += 4) {
      buffer[i] = bufferL[b];
      buffer[i + 1] = bufferL[b + 1];
      buffer[i + 2] = bufferR[b];
      buffer[i + 3] = bufferR[b + 1];
      b = b+2;
    }
    elapsedMicros usec = 0;
    frec.write(buffer, 512);  //256 or 512 (dudes code)
    Serial.print("SD write, us=");
    Serial.println(usec);
  }
}

void stopRecording() {
  Serial.println("StopRecording");
  queue1.end();
  queue2.end();
  // flush buffer
  while (queue1.available() > 0 && queue2.available() > 0) {
    queue1.readBuffer();
    queue1.freeBuffer();
    queue2.readBuffer();
    queue2.freeBuffer();
  }
  frec.close(); // close file
  mode = 4;
}}

 

[donperryjm]

Anyways, problem was AUDIO_BLOCK_SAMPLES was set to 128 in the audio library
changing to 256 solved the problem.