I have a question rearding the DRC.
The TLV320 codec have AGC (automatic gain control) on the analogue inputs, why not use the built in compression fucntion?
This might take some load off the Teensy and, more important for me, being able to route the analogue signal to lineout directly with compression.
Also, are you able to use both analogue mics at the same time as the i2s mic?
I have some ideas for a project, and I might be able to use your hardware for testing.
Best Regards Kristian Solberg
I asked this the question though email, but the answer might be interessting to more people:
I had considered using he AGC that is built into the audio codec and, yes, using it would reduce the computational load on the processor. But, using the codec’s AGC would enable a single band of compression (per audio channel). This is too simple for most hearing aid algorithms.
Most hearing aid algorithms break the audio up into multiple frequency bands, apply dynamic range compression to each band independently, and then sum the bands back together before pushing out to the earphones. So, if one is doing 4 frequency bands, the single AGC on the audio codec would not satisfy. As a result, we do it in software in the digital processor.
As for your question of using the analog mics along with the digital mics…to my knowledge, no, you cannot use both. And, worse, I can’t seem to get the digital mics to work at all. So, right now, it’s analog inputs only.
Thanks for your interest!