USB Audio in not working?

[LoopMasta]

Hi, i am trying to get audio in to my teensy 3.1 (MK20DX256 with audio shield, Audio lib 1.3.0) via usb but it stops working after ca. 1 minute. Audio out via usb or I2S works fine.

#include <Audio.h>
#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <SerialFlash.h>

AudioInputUSB            usb1;           //xy=200,69  (must set Tools > USB Type to Audio)
AudioOutputI2S           i2s1;           //xy=365,94
AudioConnection          patchCord1(usb1, 0, i2s1, 0);
AudioConnection          patchCord2(usb1, 1, i2s1, 1);
AudioControlSGTL5000     sgtl5000_1;     //xy=302,184

void setup() {
  AudioMemory(12);
  sgtl5000_1.enable();
  sgtl5000_1.volume(0.3);
}

void loop() {
  // TODO: make PC's volume setting control the SGTL5000 volume...
}

At first the audio stream sounds ok but over time it gets more and more digital artefacts until the sound is completely distorted. After a reset the sound is back to normal for ca. 1 minute.

 

[PaulStoffregen]

Maybe you're using a Mac? This is a known problem (Mac only, it works great on Windows & Linux). There's an ugly & imperfect workaround you can enable by editing usb_audio.cpp.

https://github.com/PaulStoffregen/cores/blob/master/teensy3/usb_audio.cpp#L39

Prior conversation is here. If you need more help, please comment on this thread:

https://forum.pjrc.com/threads/34855-Distorted-audio-when-using-USB-input-on-Teensy-3-1

 

[LoopMasta]

Hi Paul. Uncommenting #define MACOSX_ADAPTIVE_LIMIT works perfect. Thank you very much.

 

[PaulStoffregen]

Sadly, it's far from perfect. If you listen carefully, you'll hear a slight click every minute or so. But that's far better than the horribly distorted sound the Mac sends when asked to adapt more than it can.