Add freeze property to audiodelays.PitchShift

[relic-se]

This update adds the audiodelays.PitchShift.freeze flag to allow you to prevent any updates to the window and overlap buffer, holding the current sound to be repeated. As soon as freeze=True, normal operation resumes. This flag is reset whenever the audiosample buffer is reset as well.

Demonstration

# boot.py
import usb_audio
usb_audio.enable(
    sample_rate=16000,
)

# code.py
import audiodelays
import synthio
import time
import ulab.numpy as np
from usb_audio import usb_microphone

SAMPLE_SIZE = 1024
SAMPLE_VOLUME = 32767
ramp = np.linspace(-SAMPLE_VOLUME, SAMPLE_VOLUME, SAMPLE_SIZE, endpoint=False, dtype=np.int16)

synth = synthio.Synthesizer(
    channel_count=1,
    sample_rate=16000,
)

pitch_shift = audiodelays.PitchShift(
    mix=0.0,
    semitones=12.0,
    window=2048,
    overlap=512,
    channel_count=1,
    sample_rate=16000,
)

usb_microphone.play(pitch_shift.play(synth))

note = synthio.Note(
    frequency=synthio.midi_to_hz(60),  # middle C
    amplitude=0.25,
    waveform=ramp,
)

while True:
    print("press")
    synth.press(note)
    time.sleep(1)
    print("pitch_shift on")
    pitch_shift.mix = 0.5
    time.sleep(1)
    print("freeze")
    pitch_shift.freeze = True
    time.sleep(1)
    print("release")
    synth.release(note)
    time.sleep(1)
    print("unfreeze")
    pitch_shift.freeze = False
    time.sleep(1)
    print("pitch_shift off")
    pitch_shift.mix = 0.0
    time.sleep(1)

pitch-shift-freeze.mp3

[relic-se]

The failing test is "test_zlib_decompress_binary_bytes" within the zephyr build. Not related to this PR from what I can tell.