BlankAudio

std.BlankAudio([anode clip, int[] channels=[FRONT_LEFT, FRONT_RIGHT], int bits=16, int sampletype=INTEGER, int samplerate=44100, int length=(10*samplerate), bint keep=0, string waveform="none", float amplitude=1.0, float frequency=440.0])

Generates a new empty clip. This can be useful to have when editing audio or for testing. The default is a 10 second long 44.1kHz 16 bit stereo clip. Instead of specifying every property individually, BlankAudio can also copy the properties from clip. If both an argument such as sampletype, and clip are set, then sampletype will take precedence.

The channels argument is a list of channel constants. Specifying the same channel twice is not allowed.

The possible sampletype values are currently INTEGER (0) and FLOAT (1).

If keep is set, a reference to the same frame is returned on every request. Otherwise a new frame is generated every time. There should usually be no reason to change this setting. It has no effect when a waveform is generated since every frame is then different.

waveform:

The signal to generate. Defaults to none, which fills the clip with silence the way it always has. The other options all produce a periodic signal at frequency with a peak level of amplitude, and the same signal is written to every channel:

none

Silence.

slope

A sawtooth ramping from -1 up to +1 across each period and jumping back.

sine

A sine wave starting at zero and rising.

square

A square wave, at its positive level for the first half of each period.

triangle

A triangle starting at zero, peaking at a quarter of the way through each period and bottoming out at three quarters.

The phase of a sample depends only on its position in the clip, so a frame is identical no matter in which order frames are requested and the phase does not drift over long clips.

amplitude:

Peak level of the generated waveform, where 1.0 is full scale. Defaults to 1.0. Negative values invert the waveform.

Since integer formats reach one step further down than up, a waveform that sits exactly at full scale for a while, such as a square wave at the default amplitude, is clamped to the last representable positive value. Use a slightly lower amplitude to avoid that.

No dither is applied when generating an integer format. Generate a float clip and convert it with AudioResample if you want dithered output.

frequency:

Frequency of the generated waveform in Hz. Defaults to 440. A frequency of 0 holds the waveform at its value for phase zero, and frequencies at or above the sample rate alias the way an actual sampled signal would.

To generate a 1 kHz alignment tone at -6 dB:

BlankAudio(waveform="sine", frequency=1000, amplitude=0.5)