This directory contains a developer tool that generates and renders audio signals, via the Audio and AudioRenderer FIDL interfaces.
signal_generator [--chans=<NUM_CHANS>] [--rate=<FRAME_RATE>] [--int | --i] [--sine[=<FREQ>] | --square[=<FREQ>] | --saw[=<FREQ>] | --noise] [--amp=<AMPL>] [--dur=<DURATION>] [--ms=<MSEC>] [--wav[=<FILEPATH>]] [--rgain=<GAIN>] [--sgain=<GAIN>] [--last | --all] [--help | --?] --chans=<NUM_CHANS> Specify number of output channels (default 2) --rate=<FRAME_RATE> Set output frame rate in Hertz (default 48000) --int, --i Emit signal as 16-bit integer (default float32) --sine[=<FREQ>] Play sine of given frequency, in Hz (default 400) --square[=<FREQ>] Play square wave (default 400 Hz) --saw[=<FREQ>] Play rising sawtooth wave (default 400 Hz) --noise Play pseudo-random 'white' noise In absence of --square, --saw or --noise, a sine is played --amp=<AMPL> Set signal amplitude (full-scale=1.0, default 0.5) --dur=<DURATION> Set playback length, in seconds (default 2) --ms=<MSEC> Set data buffer size, in milliseconds (default 10) --wav[=<FILEPATH>] Save to .wav file (default /tmp/signal_generator.wav) Note: .wav file contents are unaffected by gain settings --rgain=<GAIN> Set Renderer gain to [-160.0, 24.0] dB (default 0.0) --sgain=<GAIN> Set System gain to [-160.0, 0.0] dB (default -12.0) Note: changes to System gain persist after playback. --last Set 'Play to Most-Recently-Plugged' policy --all Set 'Play to All' policy Note: changes to audio policy persist after playback. --help, --? Show this message
Developers can use this tool to manipulate two important systemwide audio settings: system (“master”) gain and audio output routing. Changes to these settings affect all audio output on the system and continue to take effect even after the signal_generator tool runs and exits. Only use --sgain, --last or --all if you intend to change the system state in a ‘sticky’ way.