Add 'AudioClip.max_volume(stereo=True)' support for more than 2 channels

CHANGELOG.md

@@ -34,6 +34,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Changed deprecated `tostring` method by `tobytes` in `video.io.gif_writers::write_gif` [\#1429](https://github.com/Zulko/moviepy/pull/1429)
 - Fixed calling `audio_normalize` on a clip with no sound causing `ZeroDivisionError` [\#1401](https://github.com/Zulko/moviepy/pull/1401)
 - Fixed `freeze` FX was freezing at time minus 1 second as the end [\#1461](https://github.com/Zulko/moviepy/pull/1461)
+- `AudioClip.max_volume(stereo=True)` now can return more than 2 channels [\#1464](https://github.com/Zulko/moviepy/pull/1464)
 
 
 ## [v2.0.0.dev2](https://github.com/zulko/moviepy/tree/v2.0.0.dev2) (2020-10-05)

moviepy/audio/AudioClip.py

@@ -157,17 +157,16 @@ def to_soundarray(
         return snd_array
 
     def max_volume(self, stereo=False, chunksize=50000, logger=None):
+        # max volume separated by channels if ``stereo`` and not mono
+        stereo = stereo and self.nchannels > 1
 
-        stereo = stereo and (self.nchannels == 2)
-
-        maxi = np.array([0, 0]) if stereo else 0
+        # zero for each channel
+        maxi = np.zeros(self.nchannels)
         for chunk in self.iter_chunks(chunksize=chunksize, logger=logger):
-            maxi = (
-                np.maximum(maxi, abs(chunk).max(axis=0))
-                if stereo
-                else max(maxi, abs(chunk).max())
-            )
-        return maxi
+            maxi = np.maximum(maxi, abs(chunk).max(axis=0))
+
+        # if mono returns float, otherwise array of volumes by channel
+        return maxi if stereo else maxi[0]
 
     @requires_duration
     @convert_path_to_string("filename")

tests/test_AudioClips.py

@@ -97,5 +97,51 @@ def test_audiofileclip_concat():
     concat.write_audiofile(os.path.join(TMP_DIR, "concat_audio_file.mp3"))
 
 
+def test_audioclip_mono_max_volume():
+    # mono
+    make_frame_440 = lambda t: np.sin(440 * 2 * np.pi * t)
+    clip = AudioClip(make_frame_440, duration=1, fps=44100)
+    max_volume = clip.max_volume()
+    assert isinstance(max_volume, float)
+    assert max_volume > 0
+
+
+@pytest.mark.parametrize(("nchannels"), (2, 4, 8, 16))
+@pytest.mark.parametrize(("channel_muted"), ("left", "right"))
+def test_audioclip_stereo_max_volume(nchannels, channel_muted):
+    def make_frame(t):
+        frame = []
+        # build channels (one of each pair muted)
+        for i in range(int(nchannels / 2)):
+            if channel_muted == "left":
+                # if muted channel is left, [0, sound, 0, sound...]
+                frame.append(np.sin(t * 0))
+                frame.append(np.sin(440 * 2 * np.pi * t))
+            else:
+                # if muted channel is right, [sound, 0, sound, 0...]
+                frame.append(np.sin(440 * 2 * np.pi * t))
+                frame.append(np.sin(t * 0))
+        return np.array(frame).T
+
+    clip = AudioClip(make_frame, fps=44100, duration=1)
+    max_volume = clip.max_volume(stereo=True)
+    # if `stereo == True`, `AudioClip.max_volume` returns a Numpy array`
+    assert isinstance(max_volume, np.ndarray)
+    assert len(max_volume) == nchannels
+
+    # check channels muted and with sound
+    for i, channel_max_volume in enumerate(max_volume):
+        if i % 2 == 0:
+            if channel_muted == "left":
+                assert channel_max_volume == 0
+            else:
+                assert channel_max_volume > 0
+        else:
+            if channel_muted == "right":
+                assert channel_max_volume == 0
+            else:
+                assert channel_max_volume > 0
+
+
 if __name__ == "__main__":
     pytest.main()