macos - record output sound in python

Question

i want to programatically record sound coming out of my laptop in python. i found PyAudio and came up with the following program that accomplishes the task:

import pyaudio, wave, sys

chunk = 1024
FORMAT = pyaudio.paInt16
CHANNELS = 1
RATE = 44100
RECORD_SECONDS = 5
WAVE_OUTPUT_FILENAME = sys.argv[1]

p = pyaudio.PyAudio()
channel_map = (0, 1)

stream_info = pyaudio.PaMacCoreStreamInfo(
    flags = pyaudio.PaMacCoreStreamInfo.paMacCorePlayNice,
    channel_map = channel_map)

stream = p.open(format = FORMAT,
                rate = RATE,
                input = True,
                input_host_api_specific_stream_info = stream_info,
                channels = CHANNELS)

all = []
for i in range(0, RATE / chunk * RECORD_SECONDS):
        data = stream.read(chunk)
        all.append(data)
stream.close()
p.terminate()

data = ''.join(all)
wf = wave.open(WAVE_OUTPUT_FILENAME, 'wb')
wf.setnchannels(CHANNELS)
wf.setsampwidth(p.get_sample_size(FORMAT))
wf.setframerate(RATE)
wf.writeframes(data)
wf.close()

the problem is i have to connect the headphone jack to the microphone jack. i tried replacing these lines:

input = True,
input_host_api_specific_stream_info = stream_info,

with these:

output = True,
output_host_api_specific_stream_info = stream_info,

but then i get this error:

Traceback (most recent call last):
File "./test.py", line 25, in
data = stream.read(chunk)
File "/Library/Python/2.5/site-packages/pyaudio.py", line 562, in read
paCanNotReadFromAnOutputOnlyStream)
IOError: [Errno Not input stream] -9975

is there a way to instantiate the PyAudio stream so that it inputs from the computer's output and i don't have to connect the headphone jack to the microphone? is there a better way to go about this? i'd prefer to stick w/ a python app and avoid cocoa.

Answer 1

You can install Soundflower, which allows you to create extra audio devices and route audio between them. This way you can define your system's output to the Soundflower device and read the audio from it using PyAudio.

You can also take a look at PyJack, an audio client for Jack.