How to convert a numpy array to a mp3 file

Question

I am using the soundcard library to record my microphone input, it records in a NumPy array and I want to grab that audio and save it as an mp3 file.

Code:

import soundcard as sc
import numpy 
import threading


speakers = sc.all_speakers() # Gets a list of the systems speakers
default_speaker = sc.default_speaker() # Gets the default speaker
mics = sc.all_microphones() # Gets a list of all the microphones


default_mic = sc.get_microphone('Headset Microphone (Arctis 7 Chat)') # Gets the default microphone


# Records the default microphone
def record_mic():
  print('Recording...')
  with default_mic.recorder(samplerate=48000) as mic, default_speaker.player(samplerate=48000) as sp:
      for _ in range(1000000000000):
          data = mic.record(numframes=None) # 'None' creates zero latency
          sp.play(data) 
          
          # Save the mp3 file here 


recordThread = threading.Thread(target=record_mic)
recordThread.start()

Answer 1

With Scipy (to wav file)

You can easily convert to wav and then separately convert wav to mp3. More details here.

from scipy.io.wavfile import write

samplerate = 44100; fs = 100
t = np.linspace(0., 1., samplerate)

amplitude = np.iinfo(np.int16).max
data = amplitude * np.sin(2. * np.pi * fs * t)

write("example.wav", samplerate, data.astype(np.int16))

With pydub (to mp3)

Try this function from this excellent thread -

import pydub 
import numpy as np

def write(f, sr, x, normalized=False):
    """numpy array to MP3"""
    channels = 2 if (x.ndim == 2 and x.shape[1] == 2) else 1
    if normalized:  # normalized array - each item should be a float in [-1, 1)
        y = np.int16(x * 2 ** 15)
    else:
        y = np.int16(x)
    song = pydub.AudioSegment(y.tobytes(), frame_rate=sr, sample_width=2, channels=channels)
    song.export(f, format="mp3", bitrate="320k")

#[[-225  707]
# [-234  782]
# [-205  755]
# ..., 
# [ 303   89]
# [ 337   69]
# [ 274   89]]

write('out2.mp3', sr, x)

Note: Output MP3 will of cause be 16-bit, because MP3s are always 16 bit. However, you can set sample_width=3 as suggested by @Arty for 24-bit input.