14: ADSR, C++ Real-Time Audio Programming with Bela

Lecture 14 of C++ Real-Time Audio Programming with Bela. This lecture covers the ADSR (attack-decay-sustain-release) envelope, implemented using state machines.
In this lecture:
Section 1: Review of state machines and envelopes 0:00
Section 2: ADSR as a state machine 9:34
Section 3: ADSR class 23:02
Section 4: Exponential ADSR 35:42
Example code and companion materials:
github.com/BelaPlatform/bela-...
This course is a deep dive into how Bela processes data, and how to implement real-time audio and interaction. If you want to learn or improve your skills with C++ and audio programming, this is a great way to start!
Bela is the open-source platform for creating beautiful interaction. If you’d like to get a Bela system to follow along with these lectures, visit shop.bela.io. Use promo code CREATEATHOME for £10 off Bela and Bela Mini Starter Kits.
Music by Vula Viel (vulaviel.com).

[@SylvainPoitras]

Working with Pure Data, I always took the shortcut to fake exponential decay presented in Andy Farnell's Designing Sound: multiplying the current envelope value by itself four times. This quartic envelope is a fairly efficient approximation of exponential decay.

[@clausanders2886]

Is there a particular reason, why you are using nested if statements instead of switch/case statements? I personally find switch statements easier to read and maintain.

[@apm414]

Good question. You can definitely use switch/case statements instead of a series of if statements, but I chose the latter for a couple reasons: first, it's simpler and less bug-prone when learning C++ (particularly forgetting to include a "break"), and second, you can't define local variables within a "case" statement which can be slightly confusing if you have more complex code to run. Ultimately it's a matter of taste, and I use plenty of switch/case in my own code.