Add an Audio display class

This is a first attempt at addressing issue 4241.

IPython/lib/display.py

@@ -4,7 +4,152 b' Authors : MinRK, gregcaporaso, dannystaple'
 """
 from os.path import exists, isfile, splitext, abspath, join, isdir
 from os import walk, sep
+import base64
+import struct
+from io import BytesIO
+import wave
+import mimetypes
+
+import numpy as np
+from IPython.core.display import DisplayObject
+
+
+class Audio(DisplayObject):
+    """Create an audio object.
+
+    When this object is returned by an input cell or passed to the
+    display function, it will result in Audio controls being displayed
+    in the frontend (only works in the notebook).
+    
+    Parameters
+    ----------
+    data : numpy array, unicode, str or bytes
+        Can be a
+        * Numpy array containing the desired waveform,
+        * String containingvthe filename
+        * Bytestring containing raw PCM data or
+        * URL pointing to a file on the web. 
+        
+        If the array option is used the waveform will be normalized.
+        
+        If a filename or url is used the format support will be browser 
+        dependent. 
+    url : unicode
+        A URL to download the data from.
+    filename : unicode
+        Path to a local file to load the data from.
+    embed : boolean
+        Should the image data be embedded using a data URI (True) or be
+        loaded using an <img> tag. Set this to True if you want the image
+        to be viewable later with no internet connection in the notebook.
+
+        Default is `True`, unless the keyword argument `url` is set, then
+        default value is `False`.
+    rate : integer
+        The sampling rate of the raw data.
+        Only required when data parameter is being used as an array
+    autoplay : bool
+        Set to True if the audio should immediately start playing.
+        Default is `False`.
+
+    Examples
+    --------
+  
+    # Generate a sound
+    import numpy as np
+    framerate = 44100
+    t = np.linspace(0,5,framerate*5)
+    data = np.sin(2*np.pi*440*np.sin(10*t**2))
+    Audio(data,rate=framerate)
+
+    Audio("http://www.nch.com.au/acm/8k16bitpcm.wav")
+    Audio(url="http://media.bradsucks.net/albums/ooi-128/01_-_Brad_Sucks_-_Dropping_out_of_School.mp3")
+    Audio(url="http://www.w3schools.com/html/horse.ogg", embed=True)
+    
+    Audio('/path/to/sound.wav')
+    Audio(filename='/path/to/sound.ogg')
+    
+    Audio(b'RAW_WAV_DATA..)
+    Audio(data=b'RAW_WAV_DATA..)
 
+    """
+        
+    def __init__(self, data=None, filename=None, url=None, embed=None, rate=None, autoplay=False):
+        if filename is None and url is None and data is None:
+            raise ValueError("No image data found. Expecting filename, url, or data.")
+        if embed is False and url is None:
+            raise ValueError("No url found. Expecting url when embed=False")
+            
+        if url is not None and embed is not True:
+            self.embed = False
+        else:
+            self.embed = True
+        self.autoplay = autoplay
+        super(Audio, self).__init__(data=data, url=url, filename=filename)
+            
+        if self.data is not None and not isinstance(self.data, bytes):
+            self.data = self._make_wav(data,rate)
+            
+    def reload(self):
+        """Reload the raw data from file or URL."""
+        if self.embed:
+            super(Audio, self).reload()
+
+        if self.filename is not None:
+            self.mimetype = mimetypes.guess_type(self.filename)[0]
+        elif self.url is not None:
+            self.mimetype = mimetypes.guess_type(self.url)[0]
+        else:
+            self.mimetype = "audio/wav"
+            
+            
+    def _make_wav(self,data,rate):
+        """ Transform a numpy array to a PCM bytestring """
+        data = np.array(data)
+        scaled = np.int16(data/np.max(np.abs(data)) * 32767)
+        fp = BytesIO()
+        waveobj = wave.open(fp,mode='wb')
+        waveobj.setnchannels(1)
+        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):
+        """shortcut for returning metadata with url information, if defined"""
+        md = {}
+        if self.url:
+            md['url'] = self.url
+        if md:
+            return self.data, md
+        else:
+            return self.data
+        
+    def _repr_html_(self):
+        src = """
+                <audio controls="controls" {autoplay}>
+                    <source src="{src}" type="{type}" />
+                    Your browser does not support the audio element.
+                </audio>
+              """
+        return src.format(src=self.src_attr(),type=self.mimetype, autoplay=self.autoplay_attr())
+
+    def src_attr(self):
+        if self.embed and (self.data is not None):
+                return """data:{type};base64,{base64}""".format(type=self.mimetype, base64=base64.encodestring(self.data))
+        elif self.url is not None:
+            return self.url
+        else:
+            return ""
+
+    def autoplay_attr(self):
+        if(self.autoplay):
+            return 'autoplay="autoplay"'
+        else:
+            return ''
 
 class IFrame(object):
     """