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I'm trying to record some sound on a Raspberry Pi using sounddevice in python. I have been following the solution from this post. When I run the program below, it all works for a short time (time may vary) and then either starts detecting no sound (volume_norm is always 0) or it hangs, eventually crashing or needing to be interrupted.

import numpy as np
import sounddevice as sd
from datetime import datetime

duration = 1800  # in seconds
scaling_factor = 100


def audio_callback(indata, frames, time, status):
    current = datetime.now()
    volume_norm = np.linalg.norm(indata) * scaling_factor
    print("{0}\t{1}".format(current.strftime("%d/%m/%Y %H:%M:%S"), volume_norm))


stream = sd.InputStream(callback=audio_callback)
with stream:
    sd.sleep(duration * 1000)

Whether the program hangs, crashes or is interrupted the same message is displayed:

Expression 'alsa_snd_pcm_drop( stream->capture.pcm )' failed in 'src/hostapi/alsa/pa_linux_alsa.c', line: 3046

I've not managed to find anything when Googling that error message. In case it's important I can check that sounddevice can detect the USB microphone and can see:

{'hostapi': 0, 'default_high_output_latency': -1.0, 'default_low_input_latency': 0.008684807256235827, 'default_samplerate': 44100.0, 'max_input_channels': 1, 'default_low_output_latency': -1.0, 'max_output_channels': 0, 'default_high_input_latency': 0.034829931972789115, 'name': 'USB PnP Sound Device: Audio (hw:1,0)'}

Please let me know if anyone knows how to solve this?

Ryan Ames
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  • I'm still trying to tackle this. I have updated PortAudio to the latest version but it still throws the same error `Expression 'alsa_snd_pcm_drop( stream->capture.pcm )' failed in 'src/hostapi/alsa/pa_linux_alsa.c', line: 3049` albeit the line number has changed slightly! Looking at the PortAudio [git repo](https://github.com/PortAudio/portaudio/blob/master/src/hostapi/alsa/pa_linux_alsa.c) it appears to be some error handling that stops a stream abruptly. – Ryan Ames Jul 07 '21 at 09:13

0 Answers0