Source Manipulation¶

We have created a source in the last section. As said previously, its properties can be manipulated to create wanted effects.

Moving the Source¶

Changing Source.position is one of the most noticeable, but first, we have to enable spatialization via Source.spatialize.

from time import sleep
from palace import Device, Context, Source, decode

with Device() as device, Context(device) as context, Source() as source:
    source.spatialize = True
    decoder = decode('some_audio.ogg')
    decoder.play(12000, 4, source)
    while source.playing:
        sleep(0.025)
        context.update()

Now, we can set the position of the source in this virtual 3D space. The position is a 3-tuple indicating the coordinate of the source. The axes are aligned according to the normal coordinate system:

The x-axis goes from left to right
The y-axis goes from below to above
The z-axis goes from front to back

For example, this will set the source above the listener:

src.position = 0, 1, 0

Note

For this too work for stereo, you have to have HRTF enabled. You can check that via Device.current_hrtf.

You can as well use a function to move the source automatically by writing a function that generate positions. A simple example is circular motion.

from itertools import takewhile, count
...
for i in takewhile(src.playing, count(step=0.025)):
    source.position = sin(i), 0, cos(-i)
    ...

A more well-written example of this can be found in our repository.

Speed and Pitch¶

Modifying pitch changes the playing speed, effectively changing pitch. Pitch can be any positive number.

src.pitch = 2    # high pitch
src.pitch = 0.4  # low pitch

Air Absorption Factor¶

Source.air_absorption_factor simulates atmospheric high-frequency air absorption. Higher values simulate foggy air and lower values simulate drier air.

src.air_absorption_factor = 9  # very high humidity
src.air_absorption_factor = 0  # dry air (default)