Add normalize parameter to Audio.

IPython/lib/display.py

@@ -1,617 +1,634 b''
 """Various display related classes.
 
 Authors : MinRK, gregcaporaso, dannystaple
 """
 from html import escape as html_escape
 from os.path import exists, isfile, splitext, abspath, join, isdir
 from os import walk, sep, fsdecode
 
 from IPython.core.display import DisplayObject, TextDisplayObject
 
 __all__ = ['Audio', 'IFrame', 'YouTubeVideo', 'VimeoVideo', 'ScribdDocument',
            'FileLink', 'FileLinks', 'Code']
 
 
 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, list, unicode, str or bytes
         Can be one of
 
           * Numpy 1d array containing the desired waveform (mono)
           * Numpy 2d array containing waveforms for each channel.
             Shape=(NCHAN, NSAMPLES). For the standard channel order, see
             http://msdn.microsoft.com/en-us/library/windows/hardware/dn653308(v=vs.85).aspx
           * List of float or integer representing the waveform (mono)
           * String containing the 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 audio data be embedded using a data URI (True) or should
         the original source be referenced. Set this to True if you want the
         audio to playable 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`.
+    normalize : bool
+        Whether audio should be normalized (rescaled) to the maximum possible
+        range. Default is `True`. When set to `False`, `data` must be between
+        -1 and 1 (inclusive), otherwise an error is raised.
+        Applies only when `data` is a list or array of samples; other types of
+        audio are never normalized.
 
     Examples
     --------
     ::
 
         # Generate a sound
         import numpy as np
         framerate = 44100
         t = np.linspace(0,5,framerate*5)
         data = np.sin(2*np.pi*220*t) + np.sin(2*np.pi*224*t)
         Audio(data,rate=framerate)
 
         # Can also do stereo or more channels
         dataleft = np.sin(2*np.pi*220*t)
         dataright = np.sin(2*np.pi*224*t)
         Audio([dataleft, dataright],rate=framerate)
 
         Audio("http://www.nch.com.au/acm/8k16bitpcm.wav")  # From URL
         Audio(url="http://www.w3schools.com/html/horse.ogg")
 
         Audio('/path/to/sound.wav')  # From file
         Audio(filename='/path/to/sound.ogg')
 
         Audio(b'RAW_WAV_DATA..)  # From bytes
         Audio(data=b'RAW_WAV_DATA..)
 
     """
     _read_flags = 'rb'
 
-    def __init__(self, data=None, filename=None, url=None, embed=None, rate=None, autoplay=False):
+    def __init__(self, data=None, filename=None, url=None, embed=None, rate=None, autoplay=False, normalize=True):
         if filename is None and url is None and data is None:
             raise ValueError("No audio 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):
             if rate is None:
                 raise ValueError("rate must be specified when data is a numpy array or list of audio samples.")
-            self.data = Audio._make_wav(data, rate)
+            self.data = Audio._make_wav(data, rate, normalize)
 
     def reload(self):
         """Reload the raw data from file or URL."""
         import mimetypes
         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"
 
     @staticmethod
-    def _make_wav(data, rate):
+    def _make_wav(data, rate, normalize):
         """ Transform a numpy array to a PCM bytestring """
         import struct
         from io import BytesIO
         import wave
 
         try:
-            scaled, nchan = Audio._validate_and_normalize_with_numpy(data)
+            scaled, nchan = Audio._validate_and_normalize_with_numpy(data, normalize)
         except ImportError:
-            scaled, nchan = Audio._validate_and_normalize_without_numpy(data)
+            scaled, nchan = Audio._validate_and_normalize_without_numpy(data, normalize)
 
         fp = BytesIO()
         waveobj = wave.open(fp,mode='wb')
         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
 
     @staticmethod
-    def _validate_and_normalize_with_numpy(data):
+    def _validate_and_normalize_with_numpy(data, normalize):
         import numpy as np
 
         data = np.array(data, dtype=float)
         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()
+        
+        max_abs_value = np.max(np.abs(data))
+        normalization_factor = Audio._get_normalization_factor(max_abs_value, normalize)
+        scaled = np.int16(data / normalization_factor * 32767).tolist()
         return scaled, nchan
 
+
     @staticmethod
-    def _validate_and_normalize_without_numpy(data):
+    def _validate_and_normalize_without_numpy(data, normalize):
         try:
-            maxabsvalue = float(max([abs(x) for x in data]))
+            max_abs_value = float(max([abs(x) for x in data]))
         except TypeError:
             raise TypeError('Only lists of mono audio are '
                 'supported if numpy is not installed')
 
-        scaled = [int(x/maxabsvalue*32767) for x in data]
+        normalization_factor = Audio._get_normalization_factor(max_abs_value, normalize)
+        scaled = [int(x / normalization_factor * 32767) for x in data]
         nchan = 1
         return scaled, nchan
 
+    @staticmethod
+    def _get_normalization_factor(max_abs_value, normalize):
+        if not normalize and max_abs_value > 1:
+            raise ValueError('Audio data must be between -1 and 1 when normalize=False.')
+        return max_abs_value if normalize else 1
+
     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):
         import base64
         if self.embed and (self.data is not None):
             data = base64=base64.b64encode(self.data).decode('ascii')
             return """data:{type};base64,{base64}""".format(type=self.mimetype,
                                                             base64=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):
     """
     Generic class to embed an iframe in an IPython notebook
     """
 
     iframe = """
         <iframe
             width="{width}"
             height="{height}"
             src="{src}{params}"
             frameborder="0"
             allowfullscreen
         ></iframe>
         """
 
     def __init__(self, src, width, height, **kwargs):
         self.src = src
         self.width = width
         self.height = height
         self.params = kwargs
 
     def _repr_html_(self):
         """return the embed iframe"""
         if self.params:
             try:
                 from urllib.parse import urlencode # Py 3
             except ImportError:
                 from urllib import urlencode
             params = "?" + urlencode(self.params)
         else:
             params = ""
         return self.iframe.format(src=self.src,
                                   width=self.width,
                                   height=self.height,
                                   params=params)
 
 class YouTubeVideo(IFrame):
     """Class for embedding a YouTube Video in an IPython session, based on its video id.
 
     e.g. to embed the video from https://www.youtube.com/watch?v=foo , you would
     do::
 
         vid = YouTubeVideo("foo")
         display(vid)
 
     To start from 30 seconds::
 
         vid = YouTubeVideo("abc", start=30)
         display(vid)
 
     To calculate seconds from time as hours, minutes, seconds use
     :class:`datetime.timedelta`::
 
         start=int(timedelta(hours=1, minutes=46, seconds=40).total_seconds())
 
     Other parameters can be provided as documented at
     https://developers.google.com/youtube/player_parameters#Parameters
     
     When converting the notebook using nbconvert, a jpeg representation of the video
     will be inserted in the document.
     """
 
     def __init__(self, id, width=400, height=300, **kwargs):
         self.id=id
         src = "https://www.youtube.com/embed/{0}".format(id)
         super(YouTubeVideo, self).__init__(src, width, height, **kwargs)
     
     def _repr_jpeg_(self):
         # Deferred import
         from urllib.request import urlopen
 
         try:
             return urlopen("https://img.youtube.com/vi/{id}/hqdefault.jpg".format(id=self.id)).read()
         except IOError:
             return None
 
 class VimeoVideo(IFrame):
     """
     Class for embedding a Vimeo video in an IPython session, based on its video id.
     """
 
     def __init__(self, id, width=400, height=300, **kwargs):
         src="https://player.vimeo.com/video/{0}".format(id)
         super(VimeoVideo, self).__init__(src, width, height, **kwargs)
 
 class ScribdDocument(IFrame):
     """
     Class for embedding a Scribd document in an IPython session
 
     Use the start_page params to specify a starting point in the document
     Use the view_mode params to specify display type one off scroll | slideshow | book
 
     e.g to Display Wes' foundational paper about PANDAS in book mode from page 3
 
     ScribdDocument(71048089, width=800, height=400, start_page=3, view_mode="book")
     """
 
     def __init__(self, id, width=400, height=300, **kwargs):
         src="https://www.scribd.com/embeds/{0}/content".format(id)
         super(ScribdDocument, self).__init__(src, width, height, **kwargs)
 
 class FileLink(object):
     """Class for embedding a local file link in an IPython session, based on path
 
     e.g. to embed a link that was generated in the IPython notebook as my/data.txt
 
     you would do::
 
         local_file = FileLink("my/data.txt")
         display(local_file)
 
     or in the HTML notebook, just::
 
         FileLink("my/data.txt")
     """
 
     html_link_str = "<a href='%s' target='_blank'>%s</a>"
 
     def __init__(self,
                  path,
                  url_prefix='',
                  result_html_prefix='',
                  result_html_suffix='<br>'):
         """
         Parameters
         ----------
         path : str
             path to the file or directory that should be formatted
         url_prefix : str
             prefix to be prepended to all files to form a working link [default:
             '']
         result_html_prefix : str
             text to append to beginning to link [default: '']
         result_html_suffix : str
             text to append at the end of link [default: '<br>']
         """
         if isdir(path):
             raise ValueError("Cannot display a directory using FileLink. "
               "Use FileLinks to display '%s'." % path)
         self.path = fsdecode(path)
         self.url_prefix = url_prefix
         self.result_html_prefix = result_html_prefix
         self.result_html_suffix = result_html_suffix
 
     def _format_path(self):
         fp = ''.join([self.url_prefix, html_escape(self.path)])
         return ''.join([self.result_html_prefix,
                         self.html_link_str % \
                             (fp, html_escape(self.path, quote=False)),
                         self.result_html_suffix])
 
     def _repr_html_(self):
         """return html link to file
         """
         if not exists(self.path):
             return ("Path (<tt>%s</tt>) doesn't exist. "
                     "It may still be in the process of "
                     "being generated, or you may have the "
                     "incorrect path." % self.path)
 
         return self._format_path()
 
     def __repr__(self):
         """return absolute path to file
         """
         return abspath(self.path)
 
 class FileLinks(FileLink):
     """Class for embedding local file links in an IPython session, based on path
 
     e.g. to embed links to files that were generated in the IPython notebook
     under ``my/data``, you would do::
 
         local_files = FileLinks("my/data")
         display(local_files)
 
     or in the HTML notebook, just::
 
         FileLinks("my/data")
     """
     def __init__(self,
                  path,
                  url_prefix='',
                  included_suffixes=None,
                  result_html_prefix='',
                  result_html_suffix='<br>',
                  notebook_display_formatter=None,
                  terminal_display_formatter=None,
                  recursive=True):
         """
         See :class:`FileLink` for the ``path``, ``url_prefix``,
         ``result_html_prefix`` and ``result_html_suffix`` parameters.
 
         included_suffixes : list
           Filename suffixes to include when formatting output [default: include
           all files]
 
         notebook_display_formatter : function
           Used to format links for display in the notebook. See discussion of
           formatter functions below.
 
         terminal_display_formatter : function
           Used to format links for display in the terminal. See discussion of
           formatter functions below.
 
         Formatter functions must be of the form::
 
             f(dirname, fnames, included_suffixes)
 
         dirname : str
           The name of a directory
         fnames : list
           The files in that directory
         included_suffixes : list
           The file suffixes that should be included in the output (passing None
           meansto include all suffixes in the output in the built-in formatters)
         recursive : boolean
           Whether to recurse into subdirectories. Default is True.
 
         The function should return a list of lines that will be printed in the
         notebook (if passing notebook_display_formatter) or the terminal (if
         passing terminal_display_formatter). This function is iterated over for
         each directory in self.path. Default formatters are in place, can be
         passed here to support alternative formatting.
 
         """
         if isfile(path):
             raise ValueError("Cannot display a file using FileLinks. "
               "Use FileLink to display '%s'." % path)
         self.included_suffixes = included_suffixes
         # remove trailing slashes for more consistent output formatting
         path = path.rstrip('/')
 
         self.path = path
         self.url_prefix = url_prefix
         self.result_html_prefix = result_html_prefix
         self.result_html_suffix = result_html_suffix
 
         self.notebook_display_formatter = \
              notebook_display_formatter or self._get_notebook_display_formatter()
         self.terminal_display_formatter = \
              terminal_display_formatter or self._get_terminal_display_formatter()
 
         self.recursive = recursive
 
     def _get_display_formatter(self,
                                dirname_output_format,
                                fname_output_format,
                                fp_format,
                                fp_cleaner=None):
         """ generate built-in formatter function
 
            this is used to define both the notebook and terminal built-in
             formatters as they only differ by some wrapper text for each entry
 
            dirname_output_format: string to use for formatting directory
             names, dirname will be substituted for a single "%s" which
             must appear in this string
            fname_output_format: string to use for formatting file names,
             if a single "%s" appears in the string, fname will be substituted
             if two "%s" appear in the string, the path to fname will be
              substituted for the first and fname will be substituted for the
              second
            fp_format: string to use for formatting filepaths, must contain
             exactly two "%s" and the dirname will be subsituted for the first
             and fname will be substituted for the second
         """
         def f(dirname, fnames, included_suffixes=None):
             result = []
             # begin by figuring out which filenames, if any,
             # are going to be displayed
             display_fnames = []
             for fname in fnames:
                 if (isfile(join(dirname,fname)) and
                        (included_suffixes is None or
                         splitext(fname)[1] in included_suffixes)):
                       display_fnames.append(fname)
 
             if len(display_fnames) == 0:
                 # if there are no filenames to display, don't print anything
                 # (not even the directory name)
                 pass
             else:
                 # otherwise print the formatted directory name followed by
                 # the formatted filenames
                 dirname_output_line = dirname_output_format % dirname
                 result.append(dirname_output_line)
                 for fname in display_fnames:
                     fp = fp_format % (dirname,fname)
                     if fp_cleaner is not None:
                         fp = fp_cleaner(fp)
                     try:
                         # output can include both a filepath and a filename...
                         fname_output_line = fname_output_format % (fp, fname)
                     except TypeError:
                         # ... or just a single filepath
                         fname_output_line = fname_output_format % fname
                     result.append(fname_output_line)
             return result
         return f
 
     def _get_notebook_display_formatter(self,
                                         spacer="&nbsp;&nbsp;"):
         """ generate function to use for notebook formatting
         """
         dirname_output_format = \
          self.result_html_prefix + "%s/" + self.result_html_suffix
         fname_output_format = \
          self.result_html_prefix + spacer + self.html_link_str + self.result_html_suffix
         fp_format = self.url_prefix + '%s/%s'
         if sep == "\\":
             # Working on a platform where the path separator is "\", so
             # must convert these to "/" for generating a URI
             def fp_cleaner(fp):
                 # Replace all occurrences of backslash ("\") with a forward
                 # slash ("/") - this is necessary on windows when a path is
                 # provided as input, but we must link to a URI
                 return fp.replace('\\','/')
         else:
             fp_cleaner = None
 
         return self._get_display_formatter(dirname_output_format,
                                            fname_output_format,
                                            fp_format,
                                            fp_cleaner)
 
     def _get_terminal_display_formatter(self,
                                         spacer="  "):
         """ generate function to use for terminal formatting
         """
         dirname_output_format = "%s/"
         fname_output_format = spacer + "%s"
         fp_format = '%s/%s'
 
         return self._get_display_formatter(dirname_output_format,
                                            fname_output_format,
                                            fp_format)
 
     def _format_path(self):
         result_lines = []
         if self.recursive:
             walked_dir = list(walk(self.path))
         else:
             walked_dir = [next(walk(self.path))]
         walked_dir.sort()
         for dirname, subdirs, fnames in walked_dir:
             result_lines += self.notebook_display_formatter(dirname, fnames, self.included_suffixes)
         return '\n'.join(result_lines)
 
     def __repr__(self):
         """return newline-separated absolute paths
         """
         result_lines = []
         if self.recursive:
             walked_dir = list(walk(self.path))
         else:
             walked_dir = [next(walk(self.path))]
         walked_dir.sort()
         for dirname, subdirs, fnames in walked_dir:
             result_lines += self.terminal_display_formatter(dirname, fnames, self.included_suffixes)
         return '\n'.join(result_lines)
 
 
 class Code(TextDisplayObject):
     """Display syntax-highlighted source code.
 
     This uses Pygments to highlight the code for HTML and Latex output.
 
     Parameters
     ----------
     data : str
         The code as a string
     url : str
         A URL to fetch the code from
     filename : str
         A local filename to load the code from
     language : str
         The short name of a Pygments lexer to use for highlighting.
         If not specified, it will guess the lexer based on the filename
         or the code. Available lexers: http://pygments.org/docs/lexers/
     """
     def __init__(self, data=None, url=None, filename=None, language=None):
         self.language = language
         super().__init__(data=data, url=url, filename=filename)
 
     def _get_lexer(self):
         if self.language:
             from pygments.lexers import get_lexer_by_name
             return get_lexer_by_name(self.language)
         elif self.filename:
             from pygments.lexers import get_lexer_for_filename
             return get_lexer_for_filename(self.filename)
         else:
             from pygments.lexers import guess_lexer
             return guess_lexer(self.data)
 
     def __repr__(self):
         return self.data
 
     def _repr_html_(self):
         from pygments import highlight
         from pygments.formatters import HtmlFormatter
         fmt = HtmlFormatter()
         style = '<style>{}</style>'.format(fmt.get_style_defs('.output_html'))
         return style + highlight(self.data, self._get_lexer(), fmt)
 
     def _repr_latex_(self):
         from pygments import highlight
         from pygments.formatters import LatexFormatter
         return highlight(self.data, self._get_lexer(), LatexFormatter())

IPython/lib/tests/test_display.py

@@ -1,209 +1,253 b''
 """Tests for IPython.lib.display.
 
 """
 #-----------------------------------------------------------------------------
 # Copyright (c) 2012, the IPython Development Team.
 #
 # Distributed under the terms of the Modified BSD License.
 #
 # The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 from tempfile import NamedTemporaryFile, mkdtemp
 from os.path import split, join as pjoin, dirname
 import sys
 try:
     import pathlib
 except ImportError:
     pass
-from unittest import mock
+from unittest import TestCase, mock
+import struct
+import wave
+from io import BytesIO
 
 # Third-party imports
 import nose.tools as nt
 import numpy
 
 # Our own imports
 from IPython.lib import display
 
 #-----------------------------------------------------------------------------
 # Classes and functions
 #-----------------------------------------------------------------------------
 
 #--------------------------
 # FileLink tests
 #--------------------------
 
 def test_instantiation_FileLink():
     """FileLink: Test class can be instantiated"""
     fl = display.FileLink('example.txt')
     # TODO: remove if when only Python >= 3.6 is supported
     if sys.version_info >= (3, 6):
         fl = display.FileLink(pathlib.PurePath('example.txt'))
 
 def test_warning_on_non_existant_path_FileLink():
     """FileLink: Calling _repr_html_ on non-existant files returns a warning
     """
     fl = display.FileLink('example.txt')
     nt.assert_true(fl._repr_html_().startswith('Path (<tt>example.txt</tt>)'))
 
 def test_existing_path_FileLink():
     """FileLink: Calling _repr_html_ functions as expected on existing filepath
     """
     tf = NamedTemporaryFile()
     fl = display.FileLink(tf.name)
     actual = fl._repr_html_()
     expected = "<a href='%s' target='_blank'>%s</a><br>" % (tf.name,tf.name)
     nt.assert_equal(actual,expected)
 
 def test_existing_path_FileLink_repr():
     """FileLink: Calling repr() functions as expected on existing filepath
     """
     tf = NamedTemporaryFile()
     fl = display.FileLink(tf.name)
     actual = repr(fl)
     expected = tf.name
     nt.assert_equal(actual,expected)
 
 def test_error_on_directory_to_FileLink():
     """FileLink: Raises error when passed directory
     """
     td = mkdtemp()
     nt.assert_raises(ValueError,display.FileLink,td)
 
 #--------------------------
 # FileLinks tests
 #--------------------------
 
 def test_instantiation_FileLinks():
     """FileLinks: Test class can be instantiated
     """
     fls = display.FileLinks('example')
 
 def test_warning_on_non_existant_path_FileLinks():
     """FileLinks: Calling _repr_html_ on non-existant files returns a warning
     """
     fls = display.FileLinks('example')
     nt.assert_true(fls._repr_html_().startswith('Path (<tt>example</tt>)'))
 
 def test_existing_path_FileLinks():
     """FileLinks: Calling _repr_html_ functions as expected on existing dir
     """
     td = mkdtemp()
     tf1 = NamedTemporaryFile(dir=td)
     tf2 = NamedTemporaryFile(dir=td)
     fl = display.FileLinks(td)
     actual = fl._repr_html_()
     actual = actual.split('\n')
     actual.sort()
     # the links should always have forward slashes, even on windows, so replace
     # backslashes with forward slashes here
     expected = ["%s/<br>" % td,
                 "&nbsp;&nbsp;<a href='%s' target='_blank'>%s</a><br>" %\
                  (tf2.name.replace("\\","/"),split(tf2.name)[1]),
                 "&nbsp;&nbsp;<a href='%s' target='_blank'>%s</a><br>" %\
                  (tf1.name.replace("\\","/"),split(tf1.name)[1])]
     expected.sort()
     # We compare the sorted list of links here as that's more reliable
     nt.assert_equal(actual,expected)
 
 def test_existing_path_FileLinks_alt_formatter():
     """FileLinks: Calling _repr_html_ functions as expected w/ an alt formatter
     """
     td = mkdtemp()
     tf1 = NamedTemporaryFile(dir=td)
     tf2 = NamedTemporaryFile(dir=td)
     def fake_formatter(dirname,fnames,included_suffixes):
         return ["hello","world"]
     fl = display.FileLinks(td,notebook_display_formatter=fake_formatter)
     actual = fl._repr_html_()
     actual = actual.split('\n')
     actual.sort()
     expected = ["hello","world"]
     expected.sort()
     # We compare the sorted list of links here as that's more reliable
     nt.assert_equal(actual,expected)
 
 def test_existing_path_FileLinks_repr():
     """FileLinks: Calling repr() functions as expected on existing directory """
     td = mkdtemp()
     tf1 = NamedTemporaryFile(dir=td)
     tf2 = NamedTemporaryFile(dir=td)
     fl = display.FileLinks(td)
     actual = repr(fl)
     actual = actual.split('\n')
     actual.sort()
     expected = ['%s/' % td, '  %s' % split(tf1.name)[1],'  %s' % split(tf2.name)[1]]
     expected.sort()
     # We compare the sorted list of links here as that's more reliable
     nt.assert_equal(actual,expected)
     
 def test_existing_path_FileLinks_repr_alt_formatter():
     """FileLinks: Calling repr() functions as expected w/ alt formatter
     """
     td = mkdtemp()
     tf1 = NamedTemporaryFile(dir=td)
     tf2 = NamedTemporaryFile(dir=td)
     def fake_formatter(dirname,fnames,included_suffixes):
         return ["hello","world"]
     fl = display.FileLinks(td,terminal_display_formatter=fake_formatter)
     actual = repr(fl)
     actual = actual.split('\n')
     actual.sort()
     expected = ["hello","world"]
     expected.sort()
     # We compare the sorted list of links here as that's more reliable
     nt.assert_equal(actual,expected)
     
 def test_error_on_file_to_FileLinks():
     """FileLinks: Raises error when passed file
     """
     td = mkdtemp()
     tf1 = NamedTemporaryFile(dir=td)
     nt.assert_raises(ValueError,display.FileLinks,tf1.name)
 
 def test_recursive_FileLinks():
     """FileLinks: Does not recurse when recursive=False
     """
     td = mkdtemp()
     tf = NamedTemporaryFile(dir=td)
     subtd = mkdtemp(dir=td)
     subtf = NamedTemporaryFile(dir=subtd)
     fl = display.FileLinks(td)
     actual = str(fl)
     actual = actual.split('\n')
     nt.assert_equal(len(actual), 4, actual)
     fl = display.FileLinks(td, recursive=False)
     actual = str(fl)
     actual = actual.split('\n')
     nt.assert_equal(len(actual), 2, actual)
 
 def test_audio_from_file():
     path = pjoin(dirname(__file__), 'test.wav')
     display.Audio(filename=path)
 
-def test_audio_from_numpy_array():
-    display.Audio(get_test_tone(), rate=44100)
-
-def test_audio_from_list_without_numpy():
-    # Simulate numpy not installed.
-    with mock.patch('numpy.array', side_effect=ImportError):
-        display.Audio(list(get_test_tone()), rate=44100)
-
-def test_audio_from_list_without_numpy_raises_for_nested_list():
-    # Simulate numpy not installed.
-    with mock.patch('numpy.array', side_effect=ImportError):
+class TestAudioDataWithNumpy(TestCase):
+    def test_audio_from_numpy_array(self):
+        test_tone = get_test_tone()
+        audio = display.Audio(test_tone, rate=44100)
+        nt.assert_equal(len(read_wav(audio.data)), len(test_tone))
+
+    def test_audio_from_list(self):
+        test_tone = get_test_tone()
+        audio = display.Audio(list(test_tone), rate=44100)
+        nt.assert_equal(len(read_wav(audio.data)), len(test_tone))
+
+    def test_audio_from_numpy_array_without_rate_raises(self):
+        nt.assert_raises(ValueError, display.Audio, get_test_tone())
+
+    def test_audio_data_normalization(self):
+        expected_max_value = numpy.iinfo(numpy.int16).max
+        for scale in [1, 0.5, 2]:
+            audio = display.Audio(get_test_tone(scale), rate=44100)
+            actual_max_value = numpy.max(numpy.abs(read_wav(audio.data)))
+            nt.assert_equal(actual_max_value, expected_max_value)
+
+    def test_audio_data_without_normalization(self):
+        max_int16 = numpy.iinfo(numpy.int16).max
+        for scale in [1, 0.5, 0.2]:
+            test_tone = get_test_tone(scale)
+            test_tone_max_abs = numpy.max(numpy.abs(test_tone))
+            expected_max_value = int(max_int16 * test_tone_max_abs)
+            audio = display.Audio(test_tone, rate=44100, normalize=False)
+            actual_max_value = numpy.max(numpy.abs(read_wav(audio.data)))
+            nt.assert_equal(actual_max_value, expected_max_value)
+
+    def test_audio_data_without_normalization_raises_for_invalid_data(self):
+        nt.assert_raises(
+            ValueError,
+            lambda: display.Audio([1.001], rate=44100, normalize=False))
+        nt.assert_raises(
+            ValueError,
+            lambda: display.Audio([-1.001], rate=44100, normalize=False))
+
+def simulate_numpy_not_installed():
+    return mock.patch('numpy.array', mock.MagicMock(side_effect=ImportError))
+
+@simulate_numpy_not_installed()
+class TestAudioDataWithoutNumpy(TestAudioDataWithNumpy):
+    # All tests from `TestAudioDataWithNumpy` are inherited.
+
+    def test_audio_raises_for_nested_list(self):
         stereo_signal = [list(get_test_tone())] * 2
-        nt.assert_raises(TypeError, lambda: display.Audio(stereo_signal, rate=44100))
-
-def test_audio_from_numpy_array_without_rate_raises():
-    nt.assert_raises(ValueError, display.Audio, get_test_tone())
-
-def get_test_tone():
-    return numpy.sin(2 * numpy.pi * 440 * numpy.linspace(0, 1, 44100))
+        nt.assert_raises(
+            TypeError,
+            lambda: display.Audio(stereo_signal, rate=44100))
+
+def get_test_tone(scale=1):
+    return numpy.sin(2 * numpy.pi * 440 * numpy.linspace(0, 1, 44100)) * scale
+
+def read_wav(data):
+    with wave.open(BytesIO(data)) as wave_file:
+        wave_data = wave_file.readframes(wave_file.getnframes())
+        num_samples = wave_file.getnframes() * wave_file.getnchannels()
+        return struct.unpack('<%sh' % num_samples, wave_data)
 
 def test_code_from_file():
     c = display.Code(filename=__file__)
     assert c._repr_html_().startswith('<style>')