closes #19; moves splice to combine

sox/combine.py

@@ -267,6 +267,9 @@ def set_input_format(self, file_type=None, rate=None, bits=None,
         self.input_format = input_format
         return self
 
+    def splice(self):
+        raise NotImplementedError
+
 
 def _validate_file_formats(input_filepath_list, combine_type):
     '''Validate that combine method can be performed with given files.

sox/transform.py

@@ -1806,10 +1806,27 @@ def silence(self, location=0, silence_threshold=0.1,
     def sinc(self):
         raise NotImplementedError
 
-    def speed(self):
-        raise NotImplementedError
+    def speed(self, factor):
+        '''Adjust the audio speed (pitch and tempo together). 
+        Technically, the speed effect only changes the sample rate information,
+        leaving the samples themselves untouched. The rate effect is invoked
+        automatically to resample to the output sample rate, using its default
+        quality/speed. For higher quality or higher speed resampling, in
+        addition to the speed effect, specify the rate effect with the desired
+        quality option.
+        
+        Parameters
+        ----------
+        factor : float
+            The ratio of the new tempo to the old tempo.
+            For ex. 1.1 speeds up the tempo by 10%; 0.9 slows it down by 10%.
+            Note - this argument is the inverse of what is passed to the sox
+            stretch effect for consistency with tempo.
 
-    def splice(self):
+        See Also
+        --------
+        tempo, pitch, rate
+        '''
         raise NotImplementedError
 
     def swap(self):

tests/test_transform.py

@@ -2354,6 +2354,42 @@ def test_buffer_around_silence_invalid(self):
             tfm.silence(buffer_around_silence=0)
 
 
+class TestTransformerSpeed(unittest.TestCase):
+
+    def test_default(self):
+        tfm = new_transformer()
+        tfm.speed(1.5)
+
+        actual_args = tfm.effects
+        expected_args = ['speed', '1.5']
+        self.assertEqual(expected_args, actual_args)
+
+        actual_log = tfm.effects_log
+        expected_log = ['speed']
+        self.assertEqual(expected_log, actual_log)
+
+        actual_res = tfm.build(INPUT_FILE, OUTPUT_FILE)
+        expected_res = True
+        self.assertEqual(expected_res, actual_res)
+
+    def test_factor_valid(self):
+        tfm = new_transformer()
+        tfm.speed(0.7)
+
+        actual_args = tfm.effects
+        expected_args = ['speed', '0.7']
+        self.assertEqual(expected_args, actual_args)
+
+        actual_res = tfm.build(INPUT_FILE, OUTPUT_FILE)
+        expected_res = True
+        self.assertEqual(expected_res, actual_res)
+
+    def test_factor_invalid(self):
+        tfm = new_transformer()
+        with self.assertRaises(ValueError):
+            tfm.speed(-1)
+
+
 class TestTransformerSwap(unittest.TestCase):
 
     def test_default(self):
@@ -2396,7 +2432,7 @@ def test_factor_valid(self):
         tfm.stretch(0.7)
 
         actual_args = tfm.effects
-        expected_args = ['stretch', '0.9', '20']
+        expected_args = ['stretch', '0.7', '20']
         self.assertEqual(expected_args, actual_args)
 
         actual_res = tfm.build(INPUT_FILE, OUTPUT_FILE)