This directory contains a developer tool that generates and outputs audio signals, via the Audio, AudioRenderer, GainControl and AudioOutputRoutingPolicy FIDL interfaces.
signal_generator [--chans=<NUM_CHANS>] [--rate=<FRAME_RATE>] [--int16 | --int24] [--sine[=<FREQ>] | --square[=<FREQ>] | --saw[=<FREQ>] | --noise] [--dur=<DURATION_SEC>] [--amp=<AMPL>] [--wav[=<FILEPATH>]] [--frames=<PACKET_SIZE>] [--gain[=<STREAM_GAIN_DB>]] [--mute[=<0|1>]] [--ramp] [--endgain=<TARGET_GAIN_DB>] [--rampdur=<RAMP_DURATION_MSEC>] [--sgain=<SYSTEM_GAIN_DB>] [--smute[=<0|1>]] [--last | --all] [--help | --?]
These optional parameters are interpreted as follows:
By default, set stream format to 2-channel float32 at 48000 Hz --chans=<NUM_CHANS> Specify number of channels --rate=<FRAME_RATE> Set frame rate in Hz --int16 Use 16-bit integer samples --int24 Use 24-in-32-bit integer samples (left-justified 'padded-24') By default, signal is a 440.0 Hz sine wave --sine[=<FREQ>] Play sine wave at given frequency (Hz) --square[=<FREQ>] Play square wave at given frequency --saw[=<FREQ>] Play rising sawtooth wave at given frequency --noise Play pseudo-random 'white' noise If no frequency is provided (e.g. '--square'), 440.0 Hz is used By default, signal plays for 2.0 seconds, at amplitude 0.25 --dur=<DURATION_SEC> Set playback length in seconds --amp=<AMPL> Set amplitude (full-scale=1.0, silence=0.0) --wav[=<FILEPATH>] Save to .wav file ('/tmp/signal_generator.wav' if only '--wav' is provided) Subsequent settings (e.g. gain) do not affect file contents By default, submit data to the renderer using buffers of 480 frames --frames=<FRAMES> Set data buffer size in frames By default, AudioRenderer gain and mute are not set (unity 0 dB, unmuted, no ramping) --gain[=<GAIN_DB>] Set stream gain (dB in [-160.0, 24.0]; 0.0 if only '--gain' is provided) --mute[=<0|1>] Set stream mute (0=Unmute or 1=Mute; Mute if only '--mute' is provided) --ramp Smoothly ramp gain from initial value to a target -75.0 dB by end-of-signal If '--gain' is not provided, ramping starts from unity gain --endgain=<GAIN_DB> Set a different ramp target gain (dB). Implies '--ramp' --rampdur=<DURATION_MS> Set a specific ramp duration in milliseconds. Implies '--ramp' By default, System Gain and Mute are unchanged --sgain[=<GAIN_DB>] Set System Gain (dB in [-160.0, 0.0]; -12.0 if only '--sgain' is provided) --smute[=<0|1>] Set System Mute (0=Unmute or 1=Mute; Mute if only '--smute' is provided) Note: changes to System Gain/Mute persist after playback By default, system audio output routing policy is unchanged --last Set 'Play to Most-Recently-Plugged' routing policy --all Set 'Play to All' routing policy Note: changes to routing policy persist after playback --help, --? Show this message
Developers can use this tool to manipulate two important systemwide audio settings: system (“master”) gain/mute and audio output routing. Changes to these settings affect all audio output on the system and continue to have effect even after the signal_generator tool runs and exits. Only use the ‘--sgain’, ‘--smute’, ‘--last’ or ‘--all’ flags if you intend to change the system state in a persistent, “sticky” way.