I2S audio popping playing samples

Support
1

Hi, I’ve bought a Pimoroni Audio Pack for the Raspberry Pico, and made some tests in CircuitPython with audio as a drum sampler.

I’ve noticed audio popping very frequently, ie. playing at default 16-bit 44100Khz kick and hi-hat sample. Feels like something about audio buffering issues, it happens 10% of the hits, which is a lot.

Do you have any guess? Can I help providing more info?

Here’s the kick.wav, and hat.wav

The code is pretty straightforward,

audio = audiobusio.I2SOut(board.GP10, board.GP11, board.GP9)
mixer = audiomixer.Mixer(voice_count=8, sample_rate=44100, channel_count=1)
audio.play(mixer)

kick = audiocore.WaveFile(open("dr55/kick.wav", "rb"))
hh = audiocore.WaveFile(open("dr55/hat.wav", "rb"))

while True
    tick = 0

    if tick % 2 == 0:
        mixer.voice[1].level = 0.1
        mixer.voice[1].play(hh)

    if tick % 8 == 0:
        mixer.voice[0].level = 0.1
        mixer.voice[0].play(kick)

    tick += 1

    time.sleep(0.05)
2

EDIT: that code snippet is part of another bigger code.

solved the issue by adding gc.collect() before playing, seems like that helps free the memory before the audiomixer does its stuff

3

however, something strange is happening: if one sample plays at all steps (~120bpm), some hits are not audible, it’s random; however if both samples plays at all steps no issues… poor wire connections