re-added pitch shift file

src/sppysound/pitch_shift.py

@@ -0,0 +1,33 @@
+import numpy as np
+import pdb
+import subprocess
+
+from audiofile import AudioFile
+
+def shift(sigin, pitch):
+    if np.isnan(pitch):
+        return sigin
+    input_filepath = "./.shift_input.wav"
+    output_filepath = "./.shift_output.wav"
+
+    shift_input = AudioFile.gen_default_wav(
+        input_filepath,
+        overwrite_existing=True,
+        mode='w',
+        channels=1,
+    )
+    # Write grain to be shifted to file
+    shift_input.write_frames(sigin)
+    # Close file
+    del shift_input
+
+    cents = 1200. * np.log2(pitch)
+    p_shift_args = ["sox", input_filepath, output_filepath, "pitch", str(cents)]
+
+    p = subprocess.Popen(p_shift_args, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    (output, err) = p.communicate()
+
+    with AudioFile(output_filepath, mode='r') as shift_output:
+        # Read result
+        result = shift_output.read_frames()
+    return result