rtmixer 0.0.0

Reliable low-latency audio playback and recording

WARNING: This is work in progress!

Goal: Reliable low-latency audio playback and recording with Python, using PortAudio via the sounddevice module.

The audio callback is implemented in C (and compiled with the help of CFFI) and doesn’t invoke the Python interpreter, therefore avoiding waiting for things like garbage collection and the GIL.

All PortAudio platforms and host APIs are supported. Runs on any Python version where CFFI is available.

Planned features:

• playback of multiple signals at the same time (fixed maximum number?)
• fixed latency playback, no jitter (optional)
• sample-accurate playback/recording (with known offset)
• non-blocking callback function, using PortAudio ringbuffer(s)
• play from memory, play from generator
• multichannel support
• meticulous reporting of overruns/underruns
• all memory allocations/deallocations happen outside of the audio callback
• loopback tests to verify correct operation and accurate latency values
• optional NumPy support?
• notification when playback is done?
• playlist/queue?

Out of scope:

• reading from/writing to files (use e.g. the soundfile module)
• realtime signal processing (inside the audio callback)
• signal generators
• multiple mixer instances (some PortAudio host APIs only support one stream at a time)
• resampling (apart from what PortAudio does)
• fade in/out
• fast forward/rewind
• panning/balance
• audio/video synchronization

Somewhat similar projects:

• https://github.com/nwhitehead/swmixer
• https://github.com/nvahalik/PyAudioMixer
• http://www.pygame.org/docs/ref/mixer.html

Installation

python3 setup.py develop --user

or

python3 -m pip install -e . --user

PortAudio doesn’t have to be installed for the compilation of the extension module, but portaudio.h must be available.

If you just want to compile the C extension module (without installing the rtmixer module), you can run this:

python3 rtmixer_build.py

Usage

import rtmixer
mixer = rtmixer.RtMixer()