fix extend_to resolves #972 and #948

changes the behavior of extend_to() so that it doesn't trim audio

opensoundscape/audio.py

@@ -587,41 +587,42 @@ def loop(self, length=None, n=None):
     def extend_to(self, duration):
         """Extend audio file to desired duration by adding silence to the end
 
-        If duration is less than the Audio's .duration, the Audio object is trimmed.
+        If `duration` is less than or equal to the Audio's self.duration, the Audio remains unchanged.
+
         Otherwise, silence is added to the end of the Audio object to achieve the desired
-        duration.
+        `duration`.
 
         Args:
-            duration: the final duration in seconds of the audio object
+            duration: the minimum final duration in seconds of the audio object
 
         Returns:
             a new Audio object of the desired duration
         """
 
-        target_n_samples = round(duration * self.sample_rate)
+        minimum_n_samples = round(duration * self.sample_rate)
         current_n_samples = len(self.samples)
 
-        if target_n_samples > current_n_samples:
+        if minimum_n_samples <= current_n_samples:
+            return self._spawn()
+
+        else:
             # add 0's to the end of the sample array
             new_samples = np.pad(
-                self.samples, pad_width=(0, target_n_samples - current_n_samples)
+                self.samples, pad_width=(0, minimum_n_samples - current_n_samples)
             )
-        elif target_n_samples < current_n_samples:
-            # trim to desired samples (similar to self.trim())
-            new_samples = self.samples[0:target_n_samples]
 
-        # update metadata to reflect new duration
-        if self.metadata is None:
-            metadata = None
-        else:
-            metadata = self.metadata.copy()
-            if "duration" in metadata:
-                metadata["duration"] = len(new_samples) / self.sample_rate
+            # update metadata to reflect new duration
+            if self.metadata is None:
+                metadata = None
+            else:
+                metadata = self.metadata.copy()
+                if "duration" in metadata:
+                    metadata["duration"] = len(new_samples) / self.sample_rate
 
-        return self._spawn(
-            samples=new_samples,
-            metadata=metadata,
-        )
+            return self._spawn(
+                samples=new_samples,
+                metadata=metadata,
+            )
 
     def extend_by(self, duration):
         """Extend audio file by adding `duration` seconds of silence to the end

tests/test_audio.py

@@ -523,12 +523,23 @@ def test_extend_to_correct_metadata(silence_10s_mp3_str):
 
 
 def test_extend_to_shorter_duration(silence_10s_mp3_str):
-    # extending 10s to 6s should simply trim the audio
+    # extending 10s to 6s should retain 10s
     audio = Audio.from_file(silence_10s_mp3_str, sample_rate=10000)
     a2 = audio.extend_to(6)
-    assert math.isclose(a2.duration, 6)
+    assert math.isclose(a2.duration, 10)
     # duration in metadata should be updated:
-    assert math.isclose(a2.metadata["duration"], 6)
+    assert math.isclose(a2.metadata["duration"], 10)
+    # other metadata should be retained:
+    assert a2.metadata["subtype"] == audio.metadata["subtype"]
+
+
+def test_extend_to_correct_duration_ok(silence_10s_mp3_str):
+    # extending 10s to 10 shouldn't raise error (#972)
+    audio = Audio.from_file(silence_10s_mp3_str, sample_rate=10000)
+    a2 = audio.extend_to(10)
+    assert math.isclose(a2.duration, 10)
+    # duration in metadata should be updated:
+    assert math.isclose(a2.metadata["duration"], 10)
     # other metadata should be retained:
     assert a2.metadata["subtype"] == audio.metadata["subtype"]