### Eric Brombaugh (@emeb)

Wireless and Audio DSP designer working in the fields of Software Defined Radio and electronic music.

## Re: Simple filter in C

Try this:http://t-filter.engineerjs.com/

## Re: Variable IIR-Filter Coefficient calculation in frequency domain

For the curve fitting approach: You need to generate a family of responses, basically a 2D surface with FFT bin weights in one axis and cutoff frequency setting...

## Re: Variable IIR-Filter Coefficient calculation in frequency domain

Option 1) is attractive as it would imply simply shifting a single fixed response up or down. You'd want to evaluate your filter response across its whole range...

## Re: The size of an FIR filter for PDM-PCM conversion

This sent me down a rabbit-hole. For 1-bit -> 16-bit you'd need a 4^15 decimation rate - roughly 2 billion, so that's clearly not what's going on in a PDM->PCM...

## Re: The size of an FIR filter for PDM-PCM conversion

Something doesn't smell right here: Wouldn't a factor of 64 bandwidth reduction only gain you 3 bits of precision?

## Re: Digital Filters that have prescribed phase shift

I haven't designed 2-arm IIR filter style Hilbert transforms from first principles myself - I assume most folks looking for such would likely begin with common...

## Re: Digital Filters that have prescribed phase shift

It's common to use a pair of allpass IIR filters with +/-45deg shifts as an analytic signal converter (aka Hilbert transform) that can generate a complex (quadrature)...

## Re: Digital down-conversion and cross-talk

By what mechanism do you anticipate crosstalk?All signal processing after the ADC is done in the digital domain. Unless there's something seriously wrong with the...

## Re: ADC and Complex Mixer Nyquist question

Here's how I'd approach this: Assuming that your ADC is sampling just a real signal, the complete spectrum of this can be viewed as 0-500MHz of the real signal,...

## Re: Extract pitch of irregular signal ?

Yes, I grabbed the clip you posted and listened to it. I also looked at it in time & frequency with Audacity. It seems to have a fairly strong peak around 377Hz...

## Re: Extract pitch of irregular signal ?

I just built a musical instrument tuner that's based on phase vocoder principles and it seems to work pretty well on irregular waveforms for estimating frequency....

## Re: FIR Convolution Compile Error

It would be very helpful if you could tell us which development tools you used that generated these errors. I do a lot of DSP work on STM32 and I've never come...

## Re: Real-Time Long FIR Convolution on STM32F769I Discovery Board

Seems like you really need to understand why your overlap/save code isn't running on the STM32 properly. Add some diagnostics to the audio processing code - toggle...

## Re: What's your favorite modern DSP chip?

ARM's Cortex-M4F claims to have "DSP instructions" but it's nowhere near as cycle-efficient as a "real" DSP would be - no simultaneous operand buses, no auto looping...

## Re: What's your favorite modern DSP chip?

Not strictly a true DSP, but I use STM32 ARM processors for a lot of audio DSP. Any of the families with Cortex M4F do quite nicely - even the low end STM32F3xx...

## Re: Audio FFT Filter, noisy clicks

As Tim noted earlier, you should be able to do the forward and inverse transforms and get virtually identical input/output. If not then you need to check your work...

Use this form to contact emeb

Before you can contact a member of the *Related Sites:

• You must be logged in (register here)
• You must confirm you email address