Add support for width and height arguments when displaying Video

Closes  #11328

docs/source/whatsnew/pr/video-width-height.rst

@@ -0,0 +1,1 b''
+``IPython.display.Video`` now supports ``width`` and ``height`` arguments, allowing a custom width and height to be set instead of using the video's width and height
  No newline at end of file

IPython/core/display.py

@@ -1256,7 +1256,8 b' class Image(DisplayObject):'
 
 class Video(DisplayObject):
 
-    def __init__(self, data=None, url=None, filename=None, embed=False, mimetype=None):
+    def __init__(self, data=None, url=None, filename=None, embed=False,
+                 mimetype=None, width=None, height=None):
         """Create a video object given raw data or an URL.
 
         When this object is returned by an input cell or passed to the
@@ -1288,6 +1289,12 b' class Video(DisplayObject):'
         mimetype: unicode
             Specify the mimetype for embedded videos.
             Default will be guessed from file extension, if available.
+        width : int
+            Width in pixels to which to constrain the video in HTML.
+            If not supplied, defaults to the width of the video.
+        height : int
+            Height in pixels to which to constrain the video in html.
+            If not supplied, defaults to the height of the video.
 
         Examples
         --------
@@ -1314,16 +1321,24 b' class Video(DisplayObject):'
 
         self.mimetype = mimetype
         self.embed = embed
+        self.width = width
+        self.height = height
         super(Video, self).__init__(data=data, url=url, filename=filename)
 
     def _repr_html_(self):
+        width = height = ''
+        if self.width:
+            width = ' width="%d"' % self.width
+        if self.height:
+            height = ' height="%d"' % self.height
+
         # External URLs and potentially local files are not embedded into the
         # notebook output.
         if not self.embed:
             url = self.url if self.url is not None else self.filename
-            output = """<video src="{0}" controls>
+            output = """<video src="{0}" controls {1} {2}>
       Your browser does not support the <code>video</code> element.
-    </video>""".format(url)
+    </video>""".format(url, width, height)
             return output
 
         # Embedded videos are base64-encoded.
@@ -1342,10 +1357,10 b' class Video(DisplayObject):'
         else:
             b64_video = b2a_base64(video).decode('ascii').rstrip()
 
-        output = """<video controls>
- <source src="data:{0};base64,{1}" type="{0}">
+        output = """<video controls {0} {1}>
+ <source src="data:{2};base64,{3}" type="{2}">
  Your browser does not support the video tag.
- </video>""".format(mimetype, b64_video)
+ </video>""".format(width, height, mimetype, b64_video)
         return output
 
     def reload(self):