Audio and DSP Programming in C++

What you will be able to do

• Represent sound as samples, and explain sample rate, bit depth, decibels and aliasing
• Process audio in blocks with std::span, mix and apply gain without clicks or clipping
• Build band-limited oscillators, envelopes and LFOs, and combine them into a small synth voice
• Follow the real-time rules of the audio thread, and prove by counting that a callback does not allocate
• Pass parameters and messages to the audio thread with atomics and a lock-free queue
• Design biquad filters, check their stability, and measure their frequency response
• Implement an FFT, choose a window, and read a spectrum correctly
• Build delay and reverb effects, and explain how a JUCE plugin is put together

Who it is for

• C++ developers who want to write audio plugins, synthesizers or game audio
• Musicians who code and want to understand what their tools do to a signal
• Engineers curious about real-time programming, where a late answer is a wrong answer
• Programmers who found signal processing too abstract in a textbook and want to run it and hear it

Before you start

• Memory & Resources
• Templates & Generic Programming
• STL & Algorithms
• Concurrency

The course project

You build a small effects-and-synth engine one block of samples at a time: oscillators and envelopes make the sound, filters shape it, delay and reverb place it in a space, and a lock-free parameter system lets another thread control it safely. Every stage plays in your browser. The last lesson wires the pieces into one plugin-shaped class with a simulated host, the same structure a JUCE plugin has.

Lessons

1. 1Sound as Numbers: Samples, Sample Rate and Your First ToneFree sampleTurn air pressure into a list of floats, write a WAV file by hand, then hear and measure what bit depth and aliasing do, including a rising scale that plays backward.50 min
2. 2Sample Buffers: Blocks, Channels, Gain and ClippingProLay out stereo audio in memory, process it in blocks with std::span, mix and apply gain in decibels, tame clipping with a soft clipper, and remove the click from a gain change.40 min
3. 3Oscillators: Phase, Waveforms and Band-LimitingProBuild sine, saw, square and triangle oscillators on a phase accumulator, measure their aliasing with a small DFT, then reduce it with PolyBLEP and wavetables.45 min
4. 4Envelopes and LFOs: Giving a Tone a ShapeProShape a raw oscillator into notes with an ADSR state machine, add tremolo, vibrato and FM, play a melody from a table, and count what polyphony and voice stealing cost.45 min
5. 5The Audio Thread: Real-Time Rules and What Breaks ThemProWhy audio code has a deadline every block, what allocation, locks, logging and denormals do to it, and how to prove by counting that a callback obeys the rules.35 min
6. 6Talking to the Audio Thread: Atomics and Lock-Free QueuesProSend parameters, messages and whole wavetables to the audio thread without locks, with atomics, a tested ring buffer and a triple buffer, and free old objects on the right thread.35 min
7. 7Filters from Scratch: Impulse Response and Frequency ResponseProBuild moving average, FIR and one-pole filters, measure their frequency response with sine tones, match it to the complex formula, and see why feedback can blow up.50 min
8. 8Biquad Filters: The Cookbook, Stability and Smooth ChangesProDesign low-pass, high-pass, band-pass, notch, peaking and shelving biquads from the Audio EQ Cookbook, check them for stability, measure their response, and change them without clicks.50 min
9. 9The FFT: Reading the Frequencies in a SignalProBuild the DFT from correlation with sines, turn it into a radix-2 FFT, read bins correctly with a Hann window, and use fast convolution, checking every step against a slower reference.45 min
10. 10Delay Lines: Echo, Chorus and Fractional DelayProBuild a circular delay line that never allocates in process, then use it for feedback echo, chorus and flanging, and measure the decay, treble loss and clicks each design choice causes.45 min
11. 11Reverb: Building a Room from Delay LinesProBuild a Schroeder reverb from comb and allpass filters, measure its RT60, add damping, move to a feedback delay network with a Householder matrix, and hear a dry hit become a room.40 min
12. 12Inside a Plugin: JUCE Structure and the Whole EngineProSee how VST3, AU, AAX and CLAP plugins are shaped, how JUCE's AudioProcessor lifecycle works, then run a complete synth and effects engine whose output does not depend on the block size.25 min