Caching#

This section covers the librosa function cache. This allows you to store and reuse intermediate computations across sessions.

Enabling the cache#

By default, caching is disabled. To enable caching, the environment variable LIBROSA_CACHE_DIR must be set prior to loading librosa. This can be done on the command line prior to instantiating a python interpreter:

$ export LIBROSA_CACHE_DIR=/tmp/librosa_cache
$ ipython

or from within python, prior to importing librosa:

>>> import os
>>> os.environ['LIBROSA_CACHE_DIR'] = '/tmp/librosa_cache'
>>> import librosa

Warning

The cache does not implement any eviction policy. As such, it can grow without bound on disk if not purged. To purge the cache directly, call:

>>> librosa.cache.clear()

Cache configuration#

The cache is implemented on top of joblib.Memory. The default configuration can be overridden by setting the following environment variables

  • LIBROSA_CACHE_DIR : path (on disk) to the cache directory

  • LIBROSA_CACHE_MMAP : optional memory mapping mode {None, ‘r+’, ‘r’, ‘w+’, ‘c’}

  • LIBROSA_CACHE_COMPRESS : flag to enable compression of data on disk {0, 1}

  • LIBROSA_CACHE_VERBOSE : controls how much debug info is displayed. {int, non-negative}

  • LIBROSA_CACHE_LEVEL : controls the caching level: the larger this value, the more data is cached. {int}

Please refer to the joblib.Memory documentation for a detailed explanation of these parameters.

As of 0.7, librosa’s cache wraps (rather than extends) the joblib.Memory object. The memory object can be directly accessed by librosa.cache.memory.

Cache levels#

Cache levels operate in a fashion similar to logging levels. For small values of LIBROSA_CACHE_LEVEL, only the most important (frequently used) data are cached. As the cache level increases, broader classes of functions are cached. As a result, application code may run faster at the expense of larger disk usage.

The caching levels are described as follows:

  • 10: filter bases, independent of audio data (mel, chroma, constant-q)

  • 20: low-level features (cqt, stft, zero-crossings, etc)

  • 30: high-level features (tempo, beats, decomposition, recurrence, etc)

  • 40: post-processing (delta, stack_memory, normalize, sync)

The default cache level is 10.