I am creating an new audio object to emplemet a HRTF(head related transfer function). to make it sound like a sound is coming from locations in space. I have this code working in MATLAB but I am having a bit of trouble getting it to work in my teensy 3.6 with the audio hat.
I need help with a few concepts.

The idea is to:
take a mono signal from the I2S input (Lsig)
duplicate mono input(Rsig)
convolv Lsig and Rsig with spacetialized filters
playout I2S convololved signals

I feel that I am missing a basic understanding of how to left and right audio channels.
Can anyone point me to the right documentation or share some wisdom with me?

This is part of what is in my update method...

// sample code
audio_block_t *blockL;
audio_block_t *blockR;
short *bpL;
short *bpR;

blockL = reciveWritable(0);
blockR = reciveWritable(1);

bpL = blockL->data;
bpR = blockR->data;

// read in buff
for (int i, i <128,i++){
buf[i] = *bpL++;
}

for (int i, i <128,i++){
*bpL++ = playbufL[i];
*bpR++ = playbufR[i];// <--gets stuck here
}
transmit(blockL,0); // does this trans only Left?
transmit(blockR,1); // does this trans only Right?
release(blockL);
release(blockR);

// fill playbufL & playbufR