Audio Input and Output from USB Microphone + Raspberry Pi

Overview

This tutorial will describe how to input audio to a Raspberry Pi using a USB microphone and furthermore how to output that audio simultaneously if needed.

Materials and Prerequisites

• USB Microphone
• Raspberry Pi
• Speaker for audio output

Process

Libraries to Install
PyAudio: Used to play and record audio on a variety of platforms. Install it by typing pip install pyaudio into the terminal
Numpy: fundamental package for scientific computing in Python. Install it by typing pip install numpy into the terminal

Code
Copy the following Python script to read audio input to wave files:

import pyaudio
import wave
import os

#The following code comes from markjay4k as referenced below
form_1 = pyaudio.paInt16
chans=1
samp_rate = 44100
chunk = 4096
record_secs = 1     #record time
dev_index = 2
wav_output_filename = 'test1.wav'


audio = pyaudio.PyAudio()

#setup audio input stream
stream=audio.open(format = form_1,rate=samp_rate,channels=chans, input_device_index = dev_index, input=True, frames_per_buffer=chunk)
print("recording")
frames=[]

for ii in range(0,int((samp_rate/chunk)*record_secs)):
    data=stream.read(chunk,exception_on_overflow = False)
    frames.append(data)

print("finished recording")

stream.stop_stream()
stream.close()
audio.terminate()

#creates wave file with audio read in
#Code is from the wave file audio tutorial as referenced below
wavefile=wave.open(wav_output_filename,'wb')
wavefile.setnchannels(chans)
wavefile.setsampwidth(audio.get_sample_size(form_1))
wavefile.setframerate(samp_rate)
wavefile.writeframes(b''.join(frames))
wavefile.close()

#plays the audio file
os.system("aplay test1.wav")

Copy the following Python script for simultaneously streaming audio output with input:

import pyaudio
import numpy as np

#The following code comes from markjay4k as referenced below

chunk=4096
RATE=44100

p=pyaudio.PyAudio()

#input stream setup
stream=p.open(format = pyaudio.paInt16,rate=RATE,channels=1, input_device_index = 2, input=True, frames_per_buffer=chunk)

#the code below is from the pyAudio library documentation referenced below
#output stream setup
player=p.open(format = pyaudio.paInt16,rate=RATE,channels=1, output=True, frames_per_buffer=chunk)

while True:            #Used to continuously stream audio
     data=np.fromstring(stream.read(chunk,exception_on_overflow = False),dtype=np.int16)
     player.write(data,chunk)
    
#closes streams
stream.stop_stream()
stream.close()
p.terminate

Authors

Pavan Narahari - Fall 2018
Sam Manyak - Fall 2018

Group Link

Crutooth

References

• The basis of the code was derived from the code developed by markjay4k, an engineer working with audio spectrum analyzers. You can find a link to his github at: https://github.com/markjay4k/Audio-Spectrum-Analyzer-in-Python
• Here is the documentation for the PyAudio Library: PyAudio
• Tutorial for audio input to wave file: https://docs.python.org/3/library/wave.html