Sorry about the delay replying, I have been away for a week, although I did see this and I have asked the internal experts about the IIR filters, I don’t have a full response yet.
The IIR filters are dedicated hardware pipelines, they are not software running on the main processor, or on the DSP.
Other little tidbits I have found are
- The filters are 5 stage IIR filters
- the filters are intended for sidetone equalization.
The consequence of 1) is you probably couldn’t do a lot of equalization for your application since there is only 5 stages, but if you are doing a very simple equalization it may be enough.
I haven’t figured out all of the consequences if 2), but I fear that you may not be able to route anything other than the MIC into the IIR filters and the output can only be routed to the speakers.
Of course I am not 100% sure about any of this, I will keep you updated as I discover more about the IIR filters.
Other related news is we are really close to enabling user programs on the DSP. When this becomes available you will be able to write your own filtering, run it on the DSP, and do any equalization your desire.
Full disclosure: I am an employee of Qualcomm Canada, any opinions I have expressed in this or any other post may not reflect the opinions of my employer.