Can the prop be a DSP (process audio signals)?

DaveF

Hey all!
Does anyone know of a way to use the propeller to process audio?· Specifically, I would like to see it be able to read levels of specific frequencies in an audio signal.

Possible?

Thanks!

Dave

Post Edited (DaveF) : 11/19/2006 6:12:09 PM GMT

potatohead

Somebody here posted an FFT object. That will get you your frequency information.

A few resistors connected to some pins will form crude DAC's. Actually they might form really good DAC's, depending on their tolerance.

It comes down to a program to grab the samples, buffer them, analyze them, and send them along their way if you want a pass thru processor. If the prop can do broadcast video and sound with two cogs, a lot of audio processing is gonna be possible.

DaveF

I found that post. I must admit, I am not familiar with FFT. I looked it up and was left scratching my head!

It sounded like that guy was on the brink of getting what I need. Maybe I should talk to him!

Is this the only way to do it?

FYI, here is that other thread:
http://forums.parallax.com/showthread.php?p=615024

DaveF

Does anyone else have any ideas?

Paul Baker

If you are looking for spectral content of a signal (many frequencies) then yes it's the best way of doing it. If you only care about the energy in a few bands you can implement digital filters. Research Infinite Impulse Response (IIR) and Finite Impulse Response (FIR) filters. There are interactive webpages on the internet which provide bandpass design capabilities and spit the filter coefficients out.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

M. K. Borri

My lab manager keeps saying that if Parallax stuff included ADCs he'd never buy anything else. [noparse]:)[/noparse]

Don Norris

Creating an audio digital filter using the Propeller chip is definitely achievable provided you use sufficient precision for the coefficients.· This means using either 16 bit integers or floating point (real) representations for the coefficients.· Then it becomes a simple matter or multiplying and accumulating partial sums.· You must also observe the Nyquist sampling rate constraint to ensure you don't create alias signals due to under-sampling.

There are also dsp chips available with compatible tool sets that may better fit this application development.· A significant difference between the Prop and the dsp is that the dsp chip architecture includes pipe-lined multipliers and accumulators to achieve significant computational efficiency as compared to a more general purpose microprocessor.

I would recommend obtaining a copy of Rorabaugh's "DSP Primer" if you want to get serious about learning and implementing digital filters.· Be forewarned that the book presumes you are familiar with C++ in order to use and/or modified·the included examples.

Good luck.

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