feat: add JSONFeatureExtractor

Parses JSON, eg that output by the pipeline or defined manually and
produces Features that can be (re-)used with the pipeline

pipeline/feature_extractors.py

@@ -1,10 +1,10 @@
 from abc import ABC
+import json
 import logging
 import os
 import random
 import subprocess
 from ast import literal_eval
-from pipeline.utils import SourceMedia, Feature, Interval
 from pipeline.utils import SourceMedia, Source, Feature, Interval
 
 # for loudness detection
@@ -332,6 +332,42 @@ class VideoActivityFeatureExtractor(FeatureExtractor):
         pass
 
 
+class JSONFeatureExtractor(FeatureExtractor):
+    """(Re-)create features from a JSON file
+
+    The JSON file can have one of two formats:
+      - the format produced by the pipleline (@see: video_producers.py:JSONProducer)
+      - a simplified format which is easier for manual creation
+    """
+
+    def __init__(self, input_files=None, config=None):
+        if not input_files:
+            raise ValueError("No input files provided!")
+        self.input_files = input_files
+        self.config = config
+        self.features = []
+
+    def setup(self):
+        pass
+
+    def _interval_from_dict(self, d):
+        return Interval(start=d["start"], duration=d["duration"])
+
+    def _source_from_dict(self, d):
+        return Source(d["source"], d["path"], d["provider"])
+
+    def run(self):
+
+        # only pipeline JSON format for now
+        # TODO: add support for simplified format
+        for file in self.input_files:
+            features_from_json = self._read_json_from_file(file.path)
+
+            for feature in features_from_json:
+                self.features.append(Feature(interval=self._interval_from_dict(feature["interval"]),
+                                             source=self._source_from_dict(feature["source"]),
+                                             feature_extractor=feature["feature_extractor"],
+                                             score=feature["score"]))
 
     def teardown(self):
         pass