implemented support for multiple channels in Audio

IPython/lib/display.py

@@ -104,24 +104,47 b' class Audio(DisplayObject):'
         import struct
         from io import BytesIO
         import wave
+
         try:
             import numpy as np
+
             data = np.array(data,dtype=float)
-            if len(data.shape) > 1:
-                raise ValueError("encoding of stereo PCM signals are unsupported")  
+            if len(data.shape) == 1:
+                nchan = 1
+            elif len(data.shape) == 2:
+                # In wave files,channels are interleaved. E.g.,
+                # "L1R1L2R2..." for stereo. See
+                # http://msdn.microsoft.com/en-us/library/windows/hardware/dn653308(v=vs.85).aspx
+                # for channel ordering
+                nchan = data.shape[0]
+                data = data.T.ravel()
+            else:
+                raise ValueError('Array audio input must be a 1D or 2D array')
             scaled = np.int16(data/np.max(np.abs(data))*32767).tolist()
         except ImportError:
+            # check that it is a "1D" list
+            idata = iter(data)  # fails if not an iterable
+            try:
+                iter(idata.next())
+                raise TypeError('Only lists of mono audio are '
+                    'supported if numpy is not installed')
+            except TypeError:
+                # this means it's not a nested list, which is what we want
+                pass
             maxabsvalue = float(max([abs(x) for x in data]))
             scaled = [int(x/maxabsvalue*32767) for x in data] 
+            nchan = 1
+
         fp = BytesIO()
         waveobj = wave.open(fp,mode='wb')
-        waveobj.setnchannels(1)
+        waveobj.setnchannels(nchan)
         waveobj.setframerate(rate)
         waveobj.setsampwidth(2)
         waveobj.setcomptype('NONE','NONE')
         waveobj.writeframes(b''.join([struct.pack('<h',x) for x in scaled]))
         val = fp.getvalue()
         waveobj.close()
+
         return val 
     
     def _data_and_metadata(self):