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The AudioGraph

Graph configuration

There are a number of graph configuration parameters that can be used to change the global behaviour of the audio system. This can be done programmatically, via a config file, or via environmental variables.

Parameter Description
output_backend_name The name of the audio output backend to use, which can be one of: jack, alsa, pulseaudio, coreaudio, wasapi, dummy. Defaults to the first of these found on the system. Typically only required for Linux.
output_device_name The name of the audio output device to use. This must precisely match the device's name in your system. If not found, DeviceNotFoundException is thrown when instantiating the graph.
output_buffer_size The size of the hardware output audio buffer, in samples. A larger buffer reduces the chance of buffer overflows and glitches, but at the cost of higher latency. Note that this config option merely specifies the preferred output buffer size, which may not be available in the system hardware. To check the actual buffer size used by the AudioGraph, query graph.output_buffer_size after instantiation.
input_device_name The name of the input device to use.
input_buffer_size The size of the hardware input audio buffer.
sample_rate The audio sample rate to use.
cpu_usage_limit Imposes a hard limit on the CPU usage permitted by SignalFlow. If the estimated (single-core) CPU usage exceeds this value, no more nodes or patches can be created until it returns to below the limit. Floating-point value between 0..1, where 0.5 means 50% CPU.

Configuring the graph programmatically

To specify an alternative config, create and populate an AudioGraphConfig object before the graph is started:

config = AudioGraphConfig()
config.output_device_name = "MacBook Pro Speakers"
config.sample_rate = 44100
config.output_buffer_size = 2048

graph = AudioGraph(config)

Configuring the graph via ~/.signalflow/config

To specify a configuration that is used by all future SignalFlow sessions, create a file ~/.signalflow/config, containing one or more of the "Graph configuration" fields listed above.

For example:

sample_rate = 48000
output_buffer_size = 256
input_buffer_size = 256
output_device_name = "MacBook Pro Speakers"
input_device_name = "MacBook Pro Microphone"

All fields are optional.

A quick and easy way to edit your config, or create a new config file, is by using the signalflow command-line utility:

signalflow configure

This will use your default $EDITOR to open the configuration, or pico if no editor is specified.

Configuring the graph via environmental variables

SignalFlow config can also be set by setting an environmental variable in your shell. Variable names are identical to the upper-case version of the config string, prefixed with SIGNALFLOW_. For example:


Printing the current config

To print the current configuration to stdout:


→ Next: Graph status and properties

Last update: 2024-01-14
Created: 2021-06-08