Add an example of phase vocoder based time stretch and pitch shift ca…

…pabilities

examples/effects.py

@@ -0,0 +1,44 @@
+import zounds
+from zounds.spectral import time_stretch, pitch_shift
+from zounds.ui import AppSettings
+import argparse
+
+sr = zounds.SR11025()
+BaseModel = zounds.stft(resample_to=sr, store_resampled=True)
+
+
+@zounds.simple_in_memory_settings
+class Sound(BaseModel):
+    pass
+
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser(parents=[
+        AppSettings()
+    ])
+    parser.add_argument(
+        '--sound-uri',
+        default='https://archive.org/download/LucaBrasi2/06-Kevin_Gates-Out_The_Mud_Prod_By_The_Runners_The_Monarch.ogg')
+    args = parser.parse_args()
+
+    _id = Sound.process(meta=args.sound_uri)
+    snd = Sound(_id)
+
+    original = snd.resampled
+    slow = zounds.AudioSamples(time_stretch(original, 0.75).squeeze(), sr)
+    fast = zounds.AudioSamples(time_stretch(original, 1.25).squeeze(), sr)
+
+    higher = zounds.AudioSamples(
+        pitch_shift(original[:zounds.Seconds(10)], 1.0).squeeze(), sr)
+    lower = zounds.AudioSamples(
+        pitch_shift(original[:zounds.Seconds(10)], -1.0).squeeze(), sr)
+
+    app = zounds.ZoundsApp(
+        model=Sound,
+        visualization_feature=Sound.fft,
+        audio_feature=Sound.resampled,
+        globals=globals(),
+        locals=locals(),
+        secret=args.app_secret)
+
+    app.start(args.port)