autobpm: Do not import 'beat' subpackage immediately to improve startup time

beetsplug/autobpm.py

@@ -15,7 +15,7 @@
 
 from typing import Iterable
 
-from librosa import beat, load
+import librosa
 from soundfile import LibsndfileError
 
 from beets import ui, util
@@ -63,7 +63,9 @@ class AutoBPMPlugin(BeetsPlugin):
                     continue
 
             try:
-                y, sr = load(util.syspath(item.path), res_type="kaiser_fast")
+                y, sr = librosa.load(
+                    util.syspath(item.path), res_type="kaiser_fast"
+                )
             except LibsndfileError as exc:
                 self._log.error(
                     "LibsndfileError: failed to load {0} {1}",
@@ -80,7 +82,7 @@ class AutoBPMPlugin(BeetsPlugin):
                 continue
 
             kwargs = self.config["beat_track_kwargs"].flatten()
-            tempo, _ = beat.beat_track(y=y, sr=sr, **kwargs)
+            tempo, _ = librosa.beat.beat_track(y=y, sr=sr, **kwargs)
             bpm = round(tempo[0] if isinstance(tempo, Iterable) else tempo)
             item["bpm"] = bpm
             self._log.info(

docs/changelog.rst

@@ -60,6 +60,10 @@ Other changes:
 * :doc:`plugins/autobpm`: Add plugin dependencies to `pyproject.toml` under
   the `autobpm` extra and update the plugin installation instructions in the
   docs.
+  Since importing the bpm calculation functionality from ``librosa`` takes
+  around 4 seconds, update the plugin to only do so when it actually needs to
+  calculate the bpm. Previously this import was being done immediately, so
+  every ``beet`` invocation was being delayed by a couple of seconds.
   :bug:`5185`
 
 2.0.0 (May 30, 2024)