Signal Generator tool

This directory contains a developer tool that generates and outputs audio signals, via the Audio, AudioRenderer, GainControl and AudioOutputRoutingPolicy FIDL interfaces.

USAGE

signal_generator
  [--chans=<NUM_CHANS>]
  [--rate=<FRAME_RATE>]
  [--int16 | --int24]
  [--sine[=<FREQ>] | --square[=<FREQ>] | --saw[=<FREQ>] | --noise]
  [--amp=<AMPL>]
  [--dur=<DURATION>]
  [--frames=<PACKET_SIZE>]
  [--wav[=<FILEPATH>]]
  [--gain=<GAIN>]
  [--sgain=<GAIN>]
  [--smute[=0|=1]]
  [--last | --all]
  [--help | --?]

These optional parameters are interpreted as follows:

--chans=<NUM_CHANS>       Specify number of output channels (default 2)
--rate=<FRAME_RATE>       Set output frame rate in Hertz (default 48000)
--int16                   Emit signal as 16-bit integer (default float32)
--int24                   Emit signal as 24-in-32-bit integer (default float32)

--sine[=<FREQ>]           Play sine of given frequency, in Hz (default 440.0)
--square[=<FREQ>]         Play square wave (default 440.0 Hz)
--saw[=<FREQ>]            Play rising sawtooth wave (default 440.0 Hz)
--noise                   Play pseudo-random 'white' noise
                          In the absence of any of the above, a sine is played.

--amp=<AMPL>              Set signal amplitude (full-scale=1.0, default 0.5)

--dur=<DURATION>          Set playback length, in seconds (default 2.0)
--frames=<PACKET_SIZE>    Set packet size, in frames (default 480)

--wav[=<FILEPATH>]        Save this signal to .wav file (default /tmp/signal_generator.wav)
                          Note: gain/mute settings do not affect .wav file contents, and
                          24-bit signals are saved left-justified in 32-bit ints.

--gain=<GAIN>             Set AudioRenderer (stream) Gain to [-160.0, +24.0] dB (default 0.0)
--sgain=<GAIN>            Set System Gain to [-160.0, 0.0] dB (default -12.0)
--smute[=<0|1>]           Set System Mute (1=mute, 0=unmute, default 1)
                          Note: changes to System Gain/Mute 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

IMPORTANT NOTE

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 take effect even after the signal_generator tool runs and exits. Only use --sgain, --smute,--last or --all if you intend to change the system state in a ‘sticky’ way.