This directory contains a developer tool that generates and outputs audio signals, via the Audio, AudioRenderer, GainControl and AudioOutputRoutingPolicy FIDL protocols.
signal_generator [--chans=<NUM_CHANS>] [--int16 | --int24] [--rate=<FRAME_RATE>] [--sine[=<FREQ>] | --square[=<FREQ>] | --saw[=<FREQ>] | --noise] [--dur=<DURATION_SEC>] [--amp=<AMPL>] [--wav[=<FILEPATH>]] [--frames=<PACKET_SIZE>] [--nbufs=<NUM_BUFFERS>] [--pts] [--threshold=<SECS>] [--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] [--settings<=ENABLED>] [--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
--int16 Use 16-bit integer samples
--int24 Use 24-in-32-bit integer samples (left-justified 'padded-24')
--rate=<FRAME_RATE> Set frame rate in Hz
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 in non-timestamped buffers of 480 frames using a single VMO.
--frames=<FRAMES> Set data buffer size in frames
--nbufs=<NUM_BUFFERS> Set the number of payload buffers to use
--pts Apply presentation timestamps (units: frames)
--threshold[=<SECS>] Set PTS discontinuity threshold, in seconds (0.0, if unspecified)
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
By default, changes to audio device settings are persisted
--settings[=<0|1>] Enable/disable creation/update of device settings
(0=Disable, 1=Enable; 0 is default if only '--settings' is provided)
--help, --? Show this message
Developers can use this tool to manipulate a few important systemwide audio settings: system (“master”) gain/mute, audio output routing, and systemwide creation/update of settings files for audio input and output devices. Changes to these settings affect all audio on the system and continue to have effect even after the signal_generator tool exits. Only use the ‘--sgain’, ‘--smute’, ‘--last’, ‘--all’ or ‘--settings’ flags when you intend to change the system state in a persistent, “sticky” way.