Decode audio files using whichever backend is available. The library
currently supports:
- `Gstreamer`_ via `gst-python`_.
- `Core Audio`_ on Mac OS X via `ctypes`_. (PyObjC not required.)
- `MAD`_ via the `pymad`_ bindings.
- `FFmpeg`_ via its command-line interface.
- The standard library `wave`_ and `aifc`_ modules (for WAV and AIFF files).