feat: adjust LoudFE._keen_num() to work as VAFE._keep_num

As with VAFE, update LoudFE to expand to min duration when keeping n features

see: 72fc6b563b

pipeline/feature_extractors.py

@@ -201,13 +201,17 @@ class LoudAudioFeatureExtractor(FeatureExtractor):
      teardown() is used to clean up temporary files created during setup (if specified by config)
     """
     _CONFIG_DEFAULT_NUM_FEATURES = 5 # keep the top 5 loudnesses
-    def __init__(self, input_files=None, config=None, num_features=_CONFIG_DEFAULT_NUM_FEATURES):
+    _CONFIG_DEFAULT_MIN_DURATION = 5.00 # seconds
+    def __init__(self, input_files=None, config=None,
+                 num_features=_CONFIG_DEFAULT_NUM_FEATURES,
+                 min_duration=_CONFIG_DEFAULT_MIN_DURATION):
         if not input_files:
             raise ValueError("No input files provided!")
         self.input_files = input_files
         self.config = config
         self.features = []
         self._num_features = num_features
+        self._min_duration = min_duration
 
     def _audio_file_from_path(self, path: str) -> str:
         """Return the audio file path given a video file path
@@ -251,9 +255,28 @@ class LoudAudioFeatureExtractor(FeatureExtractor):
 
         return loudness_features
 
-    def _keep_num(self, loudnesses, num=_CONFIG_DEFAULT_NUM_FEATURES) -> list:
-        """Keep the top n loudnesses (default: 5)"""
-        return sorted(loudnesses, key=lambda x: x[1], reverse=True)[:num]
+    def _keep_num(self, features, num=_CONFIG_DEFAULT_NUM_FEATURES) -> list:
+        """Keep the top n features (default: 5)
+
+        Approach:
+         - for range in 0-n
+           + expand the nth top feature to min duration
+            (move start back by 0.5*min_duration, end forward by 0.5*min_duration)
+           + drop any features that are now in that feature's range
+         - return the top n features
+
+        Each feature is a Feature object, with an Interval object
+        """
+        for i in range(num):
+            # expand the feature to min_duration
+            features[i].interval.move_start(-0.5*self._min_duration, relative=True)
+            features[i].interval.move_end(0.5*self._min_duration, relative=True)
+            # drop any features that are now in that feature's range
+            features = [f for f in features if
+                        f.interval.start < features[i].interval.start or
+                        f.interval.end > features[i].interval.end]
+
+        return features[:num]
 
     def setup(self):
         """extract audio from video files to be processed by pyloudnorm
@@ -272,11 +295,14 @@ class LoudAudioFeatureExtractor(FeatureExtractor):
         for file in self.input_files:
             audio_file = self._audio_file_from_path(file.path)
             loudnesses = self._loudnorm(audio_file)
-            top_loudnesses = self._keep_num(loudnesses, self._num_features)
-            for time, loudness in top_loudnesses:
-                self.features.append(Feature(interval=Interval(start=time, duration=0.500),
+
+            features = []
+            for time, loudness in loudnesses:
+                features.append(Feature(interval=Interval(start=time, duration=0.500),
                                              source=file, feature_extractor="loudness",
                                              score=loudness))
+            # prune features list to keep self.num_features
+            self.features = self._keep_num(features, self._num_features)
 
 
 class VideoActivityFeatureExtractor(FeatureExtractor):
@@ -354,7 +380,7 @@ class VideoActivityFeatureExtractor(FeatureExtractor):
         return scores[:int(len(scores) * (percent / 100))]
 
     def _keep_num(self, features, num=_CONFIG_DEFAULT_NUM_FEATURES) -> list:
-        """Keep the top n activity features (default: 5)
+        """Keep the top n features (default: 5)
 
         Approach:
          - for range in 0-n