pylastfp 0.2

Installation

To install, you will need a compiler and the dependencies required by fplib itself: fftw (compiled for single-precision floats) and libsamplerate. (On Debian/Ubuntu, the packages are libfftw3-dev and libsamplerate0-dev.)

Once you have these, you can easily install from PyPI using pip:

$ pip install pylastfp

Or, if you don’t have pip (or easy_install), head to the download page. The normal install command should work:

$ python setup.py install

To build from the version control source (i.e., not from a release tarball), you will also need Cython. (The source distributions include the generated C++ file, avoiding the need for Cython. This package’s setup.py plays tricks to detect whether you have Cython installed.)

Running

You can run the included fingerprinter/lookup script, lastmatch.py, to test your installation:

$ lastmatch.py mysterious_music.mp3

This will show metadata matches from Last.fm’s database. The script uses Gstreamer’s Python bindings to decode MP3s. You can also use pymad instead of Gstreamer (for MPEG audio only) by supplying the -m flag:

$ lastmatch.py -m mysterious_music.mp3

Using in Your Code

The script exhibits the usual way to use pylastfp, which is this:

>>> import lastfp
>>> xml = lastfp.gst_match(apikey, path)
>>> matches = lastfp.parse_metadata(xml)
>>> print matches[0]['artist'], '-', matches[0]['title']
The National - Fake Emprire

This example uses the gst_match convenience function, which uses Gstreamer to decode audio data. The function imports the Gstreamer module when called, so if you don’t want to depend on Gstreamer, just don’t call this function. Another similar function called mad_match instead imports the pymad library and uses MAD to decode instead of Gstreamer.

If you have your own way of decoding audio, you can use the lower-level interface:

>>> xml = lastfp.match(apikey, pcmdata, samplerate, time_in_secs)

Of course, you’ll need a PCM stream for the audio you want to fingerprint. The pcmdata parameter must be an iterable of Python str or buffer objects containing PCM data as arrays of C short (16-bit integer) values.

All of these functions (match, gst_match, and mad_match) accept an additional optional parameter called metadata. It should be a dict containing your current guess at the file’s metadata. Last.fm might use this information to improve their database. The dict should use these keys (all of which are optional): "artist", "album", and "track".

The module internally performs thread-safe API limiting to 5 queries per second, in accordance with Last.fm’s API TOS.

To-Do

The fingerprinting library allows for an optimization that skips decoding a few milliseconds at the beginning of every file. (See FingerprintExtractor::getToSkipMs(), as demonstrated by the example client.) Taking advantage of this will complicate the module’s interface a bit because the decoding source will need to know the amount of time to skip.

Version History

0.2

Fix a horrible memory leak. Fail safely when file is too short. Safely handle malformed XML returned from the API. Handle and expose HTTP failures.

0.1

Initial release.

Credits

This library is by Adrian Sampson. It includes the fplib source code, which is by Last.fm. fplib is licensed under the LGPLv3, so pylastfp uses the same license. pylastfp was written to be used with beets, which you should probably check out.