Signalsmith Basics

A collection of basic effects, available as plugins and re-usable open-source (MIT) C++ classes.

• Analyser
• Chorus
• Crunch
• FreqShifter
• Limiter
• Reverb

How to use

Each effect can be used just by including the corresponding header (e.g. limiter.h). This defines two classes ...Float and ...Double. Some of these have initialisation arguments (e.g. maximum lookahead) but these are always optional.

// Limiter with maximum attack/lookahead of 100ms
signalsmith::basics::LimiterFloat effect(100);

Before use, these classes must be configured. The .configure() method returns true if the config was accepted. They can be configured multiple times, but (obviously) not while actively processing audio.

effect.configure(sampleRate, maxBlockSize, channels);

To process audio, pass in a classic array-of-buffers for input and output (which shouldn't be the same):

float **inputBuffers, **outputBuffers;
int blockSize;
effect.process(inputBuffers, outputBuffers, blockSize);

When playback (re)starts, you can also call .reset() to clear any tails/state. You can also inspect latency (effect.latencySamples()) and tail length (effect.tailSamples()).

Parameters

Floating-point parameters are declared as ParamRanges in the ...STFX template. This is an opaque type which can be assigned from / converted into double from any thread. Parameter smoothing is handled internally.

Integer parameters are declared as ParamSteppeds. This is a similarly opaque type which converts to/from int.

Meters

The Analyser doesn't need any audio outputs (and will simply pass through audio if configured with them). The spectrum data is provided using the two methods .spectrumHz() and .spectrumEnergy(channel).

However, since the spectrum data is typically wanted on the main/UI thread, we need to know when it's OK to call the above methods. This is done using two "meter" methods:

• .wantsMeters(bool=true) (thread-safe) - tells the plugin whether meters should be provided
• .hasMeters() (const and thread-safe) - whether the values are ready and safe to read

After any call to .wantsMeters(), .hasMeters() will immediately return false, indicating that no thread should read meter values. If multiple threads are reading the meters, it is up to you to make sure another thread isn't calling .wantsMeters() between you checking .hasMeters() and using the values.

Implementation

The actual implementations are templates (e.g. LimiterSTFX) which you shouldn't every need to use directly, although they should be readable enough to understand the DSP and inspect parameters. These are wrapped up into the ...Float and ...Double classes by the code in stfx/stfx-library.h.

The .state() method of these templates contain a lot of detail, almost all of which is ignored (and optimised away) when using the ...Float/...Double classes. The .configureSTFX()/.processSTFX() methods are also wrapped into more typical .configure() and .process() functions.

Dependencies

Some of the effects use the submodules in modules/: DSP library, Hilbert filter, and signalsmith-linear (which provides STFTs and can wrap Accelerate/IPP).

License and support

This project is released under the MIT License. See SUPPORT.txt for the current (expected) support period and details.

If you'd like bespoke alterations to any of these effects, get in touch!