Audio (vuo.audio)

Nodes for playing audio files, receiving live audio, and synthesizing, analyzing, and filtering audio.

Audio playback

You can play an audio file using the Play Audio File node. It supports files with extension .wav, .aif, .aiff, .mp3, .mp2, .aac, .m4a, .ac3, .3gp, and .amr. To play audio from a movie file, use the Play Movie node in the vuo.video node set.

Audio devices

An audio input device (such as the MacBook Pro’s built-in microphone, or an external USB interface) can send audio to the Receive Live Audio node, allowing the audio to control the composition.

An audio output device (such as the MacBook Pro’s built-in speakers, or an external USB interface) can receive audio from the Send Live Audio node, allowing you to hear audio that was read from a movie or sound file, or synthesized within Vuo.

Each audio device has a unique ID, which is assigned by the operating system. If all devices were plugged in after the computer started up, then ID 0 is usually the first device plugged in, ID 1 is usually the second device plugged in, etc.

Each audio device has a name, which is not necessarily unique. On macOS, you can look up a device’s name in the Audio MIDI Setup application. The device’s name may change depending on the system’s language settings or the port the device is connected to.

Each audio device also has a model code, which is the same for a given model regardless of system language settings and the port the device is connected to. Use the List Audio Devices node to see the model code for each device.

Audio signals

Each audio device has one or more channels. A channel is an independent audio signal — for example, in stereo audio, there are two channels: left and right. In stereo, typically, left is channel 1 and right is channel 2. You can look up a device’s channel numbers in the Audio MIDI Setup application.

A continuous stream of audio is broken up into slices called samples. Each sample is a measurement of the amplitude of the audio signal, which represents how much the physical airwaves are compressed or expanded at that instant in time. In Vuo, each sample is typically a number between -1 and 1. On macOS, you can configure the sample rate in the Audio MIDI Setup application. Higher sample rates result in a more accurate digital reproduction of the audio signal, but also require more computational power.

The Receive Live Audio node fires an event each time a new sample buffer is received. A sample buffer is a collection of 512 audio samples. Samples are grouped into buffers in order to improve efficiency.

Each event from the Receive Live Audio node provides a sample buffer for each channel. You can split up the channels and analyze them individually using the Calculate Loudness node, or you can combine them first using the Mix Audio Channels node.


Example compositions:


Nodes: