Blog
This started by tidying up some of the notes I took while working on audio/DSP stuff, but it's become a project of its own.
Latest post
Filter-Bank Spectra (and Pitch-Tracking)
Geraint LuffSignalsmith Audio Ltd.
Non-uniform spectrum analysis and how it can be useful
I didn't get to talk at ADC this year, so this is pretty much my would-be-presentation in blog form. 😄
Investigations
Things I figured out up with while trying to solve a problem... or just having fun. 🙂
Cascaded box-filter smoothing filters
Geraint LuffSignalsmith Audio Ltd. original
We combine box-filters to create a family of cheap FIR smoothing filters, and provide some optimal sizes.
Stride-Interpolated Delay
Geraint Luff original
When we change the length of a delay-line, we usually use either a smooth slide (with detuning) or a cross-fade (with comb-filtering artefacts). Let's look at a third option!
Analytic pluck synthesis
Geraint Luff original
No feedback, no wavetables, no aliasing: synthesising a plucked-string sound using a family of directly-computable band-limited impulses.
A cheap energy-preserving-ish crossfade
Geraint Luff original
A fun little polynomial cross-fade curve with (almost) constant energy, extended into a family of curves for fractional power-laws.
Effects
Guides to some designs for particular audio effects. The reverb one was presented at ADC21.
Warmer waveshapers
Geraint LuffSignalsmith Audio Ltd.
Looking at a couple of ways to reduce the bright high-end you commonly get from waveshaping distortion, while preserving clarity.
Designing a straightforward limiter
Geraint LuffSignalsmith Audio Ltd.
We set out some requirements for a brick-wall limiter, have a go at solving them, and sketch out some ways it could be modified.
Let's Write A Reverb
Geraint LuffNo magic numbers, no tricky tuning: a clean and flexible approach to designing a smooth high-quality reverb, using a variation on the classic feedback-delay network (FDN) structure.
It's not quite a how-to guide (the ADC22 talk is closer to that), but here are some particular choices for our Signalsmith Stretch library:
Technical Tidbits
Technical stuff I thought was interesting!
Filter-Bank Spectra (and Pitch-Tracking)
Geraint LuffSignalsmith Audio Ltd.
Non-uniform spectrum analysis and how it can be useful
Constant-time peak-hold
Geraint LuffSignalsmith Audio Ltd.
Looking at some ways to implement peak-hold (sliding maximum), including one with constant O(1) complexity.
Smooth Monotonic Interpolation
Geraint Luff
Producing a smooth, intuitive curve from a set of control points.
Invertible fixed-point complex rotation
Geraint Luff
A look at how to perform lossless rotations on integer / fixed-point co-ordinates or complex values.
Box-filters without accumulating errors
Geraint LuffSignalsmith Audio Ltd.
Exploring some ways to efficiently calculate box filters without accumulating floating-point errors, including varying-width filters.
Extra-wide window functions
Geraint Luff
Window functions are typically matched to the length of your FFT, but they don't have to be. Let's look at how we can use a window longer than the FFT size.