Play and Record Sound with Python
- Source code repository and issue tracker:
- MIT – see the file LICENSE for details.
- Of course, you’ll need Python. Any version where CFFI (see below) is supported should work. If you don’t have Python installed yet, you should get one of the distributions which already include CFFI and NumPy (and many other useful things), e.g. Anaconda or WinPython.
Those are needed for the installation of the Python module and its dependencies. Most systems will have these installed already, but if not, you should install it with your package manager or you can download and install pip and setuptools as described on the pip installation page. If you happen to have pip but not setuptools, use this command:
python3 -m pip install setuptools --user
The C Foreign Function Interface for Python is used to access the C-API of the PortAudio library from within Python. It supports CPython 2.6, 2.7, 3.x; and is distributed with PyPy. If it’s not installed already, you should install it with your package manager (the package might be called python3-cffi or similar), or you can get it with:
python3 -m pip install cffi --user
- PortAudio library:
- The PortAudio library must be installed on your system (and CFFI must be able to find it). Again, you should use your package manager to install it (the package might be called libportaudio2 or similar). If you prefer, you can of course also download the sources and compile the library yourself. If you are using Mac OS X or Windows, the library will be installed automagically with pip (see “Installation” below).
- NumPy (optional):
- NumPy is only needed if you want to play back and record NumPy arrays. The classes sounddevice.RawStream, sounddevice.RawInputStream and sounddevice.RawOutputStream use plain Python buffer objects and don’t need NumPy at all. If you need NumPy, you should install it with your package manager or use a Python distribution that already includes NumPy (see above). Installing NumPy with pip requires a compiler and several additional libraries and is therefore not recommended for beginners.
Once you have installed the above-mentioned dependencies, you can use pip to download and install the latest release with a single command:
python3 -m pip install sounddevice --user
If you want to install it system-wide for all users (assuming you have the necessary rights), you can just drop the --user option.
To un-install, use:
python3 -m pip uninstall sounddevice
If you are using Windows, you can alternatively install one of the packages provided at http://www.lfd.uci.edu/~gohlke/pythonlibs/#sounddevice. The PortAudio library is also included in the package and you can get the rest of the dependencies on the same page.
First, import the module:
import sounddevice as sd
Assuming you have a NumPy array named myarray holding audio data with a sampling frequency of fs (in the most cases this will be 44100 or 48000 frames per second), you can play it back with sounddevice.play():
This function returns immediately but continues playing the audio signal in the background. You can stop playback with sounddevice.stop():
If you know that you will use the same sampling frequency for a while, you can set it as default using sounddevice.default.samplerate:
sd.default.samplerate = fs
After that, you can drop the samplerate argument:
To record audio data from your sound device into a NumPy array, use sounddevice.rec():
duration = 10.5 # seconds myrecording = sd.rec(int(duration * fs), samplerate=fs, channels=2)
Again, for repeated use you can set defaults using sounddevice.default:
sd.default.samplerate = fs sd.default.channels = 2
After that, you can drop the additional arguments:
myrecording = sd.rec(duration * fs)
This function also returns immediately but continues recording in the background. In the meantime, you can run other commands. If you want to check if the recording is finished, you should use sounddevice.wait():
If the recording was already finished, this returns immediately; if not, it waits and returns as soon as the recording is finished.
Alternatively, you could have used the blocking argument in the first place:
myrecording = sd.rec(duration * fs, blocking=True)
By default, the recorded array has the data type 'float32' (see sounddevice.default.dtype), but this can be changed with the dtype argument:
myrecording = sd.rec(duration * fs, dtype='float64')
Simultaneous Playback and Recording
To play back an array and record at the same time, use sounddevice.playrec():
myrecording = sd.playrec(myarray, fs, channels=2)
The number of output channels is obtained from myarray, but the number of input channels still has to be specified.
Again, default values can be used:
sd.default.samplerate = fs sd.default.channels = 2 myrecording = sd.playrec(myarray)
In this case the number of output channels is still taken from myarray (which may or may not have 2 channels), but the number of input channels is taken from sounddevice.default.channels.
In many cases, the default input/output device(s) will be the one(s) you want, but it is of course possible to choose a different device. Use sounddevice.query_devices() to get a list of supported devices. The same list can be obtained from a terminal by typing the command
python3 -m sounddevice
You can use the corresponding device ID to select a desired device by assigning to sounddevice.default.device or by passing it as device argument to sounddevice.play(), sounddevice.Stream() etc.
Instead of the numerical device ID, you can also use a space-separated list of case-insensitive substrings of the device name (and the host API name, if needed). See sounddevice.default.device for details.
import sounddevice as sd sd.default.samplerate = 44100 sd.default.device = 'digital output' sd.play(myarray)
Callback “wire” with sounddevice.Stream:
import sounddevice as sd duration = 5.5 # seconds def callback(indata, outdata, frames, time, status): if status: print(status) outdata[:] = indata with sd.Stream(channels=2, callback=callback): sd.sleep(int(duration * 1000))
Same thing with sounddevice.RawStream:
import sounddevice as sd duration = 5.5 # seconds def callback(indata, outdata, frames, time, status): if status: print(status) outdata[:] = indata with sd.RawStream(channels=2, dtype='int24', callback=callback): sd.sleep(int(duration * 1000))
We are using 24-bit samples here for no particular reason (just because we can).
Blocking Read/Write Streams
Instead of using a callback function, you can also use the blocking methods sounddevice.Stream.read() and sounddevice.Stream.write() (and of course the corresponding methods in sounddevice.InputStream, sounddevice.OutputStream, sounddevice.RawStream, sounddevice.RawInputStream and sounddevice.RawOutputStream).
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