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:
[audio]
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:
export SIGNALFLOW_OUTPUT_DEVICE_NAME="MacBook Pro Speakers"
export SIGNALFLOW_OUTPUT_BUFFER_SIZE=1024
Printing the current config
To print the current configuration to stdout:
graph.config.print()
→ Next: Graph status and properties
Created: 2021-06-08