Convert PyAudio microphone input stream to mp3

Question

I am looking for ways to directly encode mp3 files from the microphone without saving to an intermediate wav file. There are tons of examples for saving to a wav file out there and a ton of examples for converting a wav file to mp3. But I have had no luck finding a way to save an mp3 directly from the mic. For example I am using the below example found on the webs to record to a wav file.

Am hoping to get suggestions on how to convert the frames list (pyaudio stream reads) to an mp3 directly. Or alternatively, stream the pyaudio microphone input directly to an mp3 via ffmpeg without populating a list/array with read data. Thank you very much!

import pyaudio
import wave

# the file name output you want to record into
filename = "recorded.wav"
# set the chunk size of 1024 samples
chunk = 1024
# sample format
FORMAT = pyaudio.paInt16
# mono, change to 2 if you want stereo
channels = 1
# 44100 samples per second
sample_rate = 44100
record_seconds = 5
# initialize PyAudio object
p = pyaudio.PyAudio()
# open stream object as input & output
stream = p.open(format=FORMAT,
                channels=channels,
                rate=sample_rate,
                input=True,
                output=True,
                frames_per_buffer=chunk)
frames = []
print("Recording...")
for i in range(int(44100 / chunk * record_seconds)):
    data = stream.read(chunk)
    frames.append(data)
print("Finished recording.")
# stop and close stream
stream.stop_stream()
stream.close()
# terminate pyaudio object
p.terminate()
# save audio file
# open the file in 'write bytes' mode
wf = wave.open(filename, "wb")
# set the channels
wf.setnchannels(channels)
# set the sample format
wf.setsampwidth(p.get_sample_size(FORMAT))
# set the sample rate
wf.setframerate(sample_rate)
# write the frames as bytes
wf.writeframes(b"".join(frames))
# close the file
wf.close()

Answer 1

I was able to find a way to convert the pyaudio pcm stream to mp3 without saving to an intermediate wav file using a lame 3.1 binary from rarewares. I'm sure it can be done with ffmpeg as well but since ffmpeg uses lame to encode to mp3 I thought I would just focus on lame.

For converting the raw pcm array to an mp3 directly, remove all the wave file operations and replace with the following. This pipes the data into lame all in one go.

raw_pcm = b''.join(frames)
l = subprocess.Popen("lame - -r -m m recorded.mp3", stdin=subprocess.PIPE)
l.communicate(input=raw_pcm)

For piping the pcm data into lame as it is read, I used the following. I'm sure you could do this in a stream callback if you wished.

l = subprocess.Popen("lame - -r -m m recorded.mp3", stdin=subprocess.PIPE)
for i in range(int(44100 / chunk * record_seconds)):
    l.stdin.write(stream.read(chunk))

I should note, that either way, lame did not start encoding until after the data was finished piping in. When piping in the data on each stream read, I assumed the encoding would start right away, but that was not the case.

Also, using .stdin.write may cause some trouble if stdout and stderr buffers arent read. Something I need to look into further.