Tag: audio

Over the last few weeks I ported the libebur128 C library to Rust, both with a proper Rust API as well as a 100% compatible C API.

A few months ago I wrote a new GStreamer plugin: an audio filter for live loudness normalization and automatic gain control.

Its code is based on Kyle Swanson’s great FFmpeg filter af_loudnorm, about which he wrote some more technical details on his blog a few years back. I’m not going to repeat all that here, if you’re interested in those details and further links please read Kyle’s blog post.

From a very high-level, the filter works by measuring the loudness of the input following the EBU R128 standard with a 3s lookahead, adjusts the gain to reach the target loudness and then applies a true peak limiter with 10ms to prevent any too high peaks to get passed through. Both the target loudness and the maximum peak can be configured via the loudness-target and max-true-peak properties, same as in the FFmpeg filter. Different to the FFmpeg filter I only implemented the “live” mode and not the two-pass mode that is implemented in FFmpeg, which first measures the loudness of the whole stream and then in a second pass adjusts it.

Below I’ll describe the usage of the filter in GStreamer a bit and also some information about the development process, and the porting of the C code to Rust.

I ported a C library to rust last week, and it went pretty smoothly. The library in question is RNNoise, a library for removing noise from audio. It works well, it runs fast, and best of all it has no knobs that you need to tune. There’s even a rust
binding.

Wavetable Synthesis is a method for synthesizing audio by interpolating between different pre-sampled waveforms stored in a table. It's a very neat way to generate sounds that change over time, allowing the different waveforms to morph into each other slowly in order to create rich and complicated textures.

I've been experimenting with synthesizing audio in the web browser via my web-based DSP project, and figured that wavetable synthesis would be a cool addition to the platform. It seemed like a simple enough thing to implement from scratch and an awesome opportunity to put Rust and WebAssembly to work in a useful way! As it turns out, it's both a really well-fitting usecase for Rust/Wasm and terrific context for a tour of the broader WebAudio landscape.

In this post, we'll throw something random into, well, a math-oven and viola, music! We'll just skip the crash. In other words, we're going to teach our computers to "sing" using idiomatic Rust, backed by a little light physics and music theory.

Shortwave is an internet radio player that lets you search for stations, listen to them and record songs automatically.

In my spare time I’m an emergency services volunteer, and one of the tasks our unit has is to run the radio network and keep track of what’s happening. This can be a pretty stressful job, especially when there’s lots of radio traffic, and it’s not unusual to miss words or entire transmissions.

To help with a personal project that could make the job easier I’d like to implement a basic component of audio processing, the Noise Gate.