Realtime EQ + Reverb

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Shuptuu

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Hi,
Can anybody tell me if would be doable to embed in a teensy board with the audio adapter board, a mono 4bands parametric EQ and a reverb (chained), the whole thing working in realtime (meaning with a very low time processing or low latency)?
Do I have to go directly for a teensy 3.6 to handle this kind of job?
What kind of performence can I expect from this?
(already using teensy boards for midi applications, works great! but never tried with audio...)
Thanks for your help!
Olivier
 
Probably depends on how you'd implement the 4 filters. As biquads, I'd say Teensy 3.2 is pretty likely to work. As long response FIR, you might need to step up to Teensy 3.6.

You can expect latency to be about 6 ms for the input & output of data buffering, plus about 1 ms in the hardware, of course added to the effective delay of your filters.
 
I'm currently doing performance optimization on my analog audio delay module which uses an 8th order IIR filter broken down into four biquad stages.

Just to give you some numbers on what I saw (trying to recall from memory): on a T3.2, it takes about 25% of the processor and the T3.6 is about half that for 4 stages, the rest of the processing is very lightweight. So, very roughly speaking, I think I'm seeing 6% utilization per stage of biquad. I'm assuming utilization will scale linearly with the number of biquads stages. Based on that you can probably have about 15 stages of biquad on a T3.2 and 30 on at T3.6.

It's also possible I'm doing something inefficient and performance could be even better but you should at least get this.
 
You might also want to try the built-in-EQ of the codec hardware in the Teensy audio board:

https://www.pjrc.com/teensy/gui/?info=AudioControlSGTL5000

This gives you a five-band-EQ without additional load on the Teensy processor itself.

And its quite easy to use, see the GUI under the link above.

It performs quite well, although it seems not many people use it. My experience is good with that EQ.

Have fun with the Teensy,

Frank

P.S.: or you try the 7-band parametric equalizer which is basically the same as a cascade of 7 biquad IIRs, but there you would have to provide the filter coefficients by yourself. Probably best to use some program to calculate them, eg. Iowa Hills IIR Filter designer, very good.
 
Thank you for all these answers. Really interesting!
Thanks DD4WH: I was not aware of that built-in EQ in the teensy audio board. Sounds a really good option.
Olivier
 
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