playing sine wave on raspberry pi has 25+ seconds delay before sound starts to play

I have been testing sounddevice to play a sine wave (based on the code example in the docs). Everything works - but after I start the output stream, it takes about 25-30 seconds before the sine wave sound starts to play. On a Raspberry pi 3B - I did a clean latest rasbian buster light install - running headless (SSH from mac), and only installed what was necessary for sounddevice and soundfile. Installed python 3.9.4 - but I had the same problem when I was running 3.7 that came with the OS (playing the wave file example). I can use aplay on the RPi to play a sound wave no problem (no delay)

I initially used the code from sine wave example with outputstream(...) - and but then changed to creating the stream first and start it separately: same result. I inserted a bunch of calls to time.time() - I can see the stream starts right away but the first call to the callback takes 25-30 seconds.

My Code:

import sounddevice as sd
import numpy as np 

start_idx = 0
cnt=1
sd.default.device=0


try:
    samplerate = 44100

    def callback(outdata, frames, time, status):
        if status:
            print(status, file=sys.stderr)
        global start_idx
        global cnt
        t = (start_idx + np.arange(frames)) / samplerate
        t = t.reshape(-1, 1)
        outdata[:] = 1 * np.sin(2 * np.pi * 440 * t) 
        start_idx += frames
        cnt+=1
        if cnt>20: 
            print('count =',cnt)
            raise sd.CallbackStop

    myStream=sd.OutputStream(device=0, channels=1, callback=callback,
                         samplerate=samplerate)
    myStream.start()
    print('stream is active: ',myStream.active).   #This shows True
    print('cpu load = ',myStream.cpu_load).        #This shows 0.0
    input()  # (I wait until I see count=21 printed in terminal and sound stops in headphones, then hit return )
    myStream.stop()
    myStream.close()

For info - sd.query_devices() yields:

* 0 bcm2835 Headphones: - (hw:0,0), ALSA (0 in, 8 out)
  1 Logitech USB Microphone: Audio (hw:1,0), ALSA (1 in, 0 out)
  2 sysdefault, ALSA (0 in, 128 out)
  3 output, ALSA (0 in, 8 out)
  4 dmix, ALSA (0 in, 2 out)
  5 default, ALSA (0 in, 128 out)

any ideas why this happens? could it be a PortAudio issue on the pi - nothing to do with sounddevice?

[HaHeho]

I believe this can be closed then.

[josephernest]

Good news!

apt update
apt install raspberrypi-kernel

solves it 😃