CC3220SF-LAUNCHXL: i2sWrite with audioboost codec issues using i2secho example

Using the example it is not clear why there are 3 NUMDESC ? Also, the example uses a i2sWriteReclaim / i2sReadReclaim which I can probably do without as all I need to do is send data to the codec.

Having tried to write out to the codec of an incoming set of UDP  buffers using i2sWrite without success, is there another method to write to the audio codec?

while(1) {

...reads from UDP and buffers into sample_out...

cb_audio_out.bufPtr = audio_out_ptr; // sample_out
cb_audio_out.bufSize = AUDIO_BUFFER_SIZE;
bytesSent = I2S_write(i2sHandle, &cb_audio_out);
audio_out_ptr += AUDIO_SAMPLE_BUFFER_SIZE/sizeof(uint32_t);
b++;

}