Add tfdt parsing

Parse out a track fragment decode time box. According to the Media Source byte stream format spec, at least one tfdt is required per media segment.

@@ -594,7 +594,7 @@ test('can parse an styp', function() {
     majorBrand: 'avc1',
     minorVersion: 2,
     compatibleBrands: [3, 4]
-  }], 'parsed an ftyp');
+  }], 'parsed an styp');
 });
 
 test('can parse a vmhd', function() {
@@ -767,6 +767,21 @@ test('can parse a sidx', function(){
             }]);
 });
 
+test('can parse a tfdt', function() {
+  var data = box('tfdt',
+                 0x00, // version
+                 0x00, 0x00, 0x00, // flags
+                 0x01, 0x02, 0x03, 0x04); // baseMediaDecodeTime
+  deepEqual(videojs.inspectMp4(new Uint8Array(data)),
+            [{
+              type: 'tfdt',
+              version: 0,
+              size: 16,
+              flags: new Uint8Array([0, 0, 0]),
+              baseMediaDecodeTime: 0x01020304
+            }]);
+});
+
 test('can parse a series of boxes', function() {
   var ftyp = [
     0x00, 0x00, 0x00, 0x18 // size 4 * 6 = 24

@@ -376,6 +376,13 @@ var
     styp: function(data) {
       return parse.ftyp(data);
     },
+    tfdt: function(data) {
+      return {
+        version: data[0],
+        flags: new Uint8Array(data.subarray(1, 4)),
+        baseMediaDecodeTime: data[4] << 24 | data[5] << 16 | data[6] << 8 | data[7]
+      };
+    },
     tfhd: function(data) {
       var
         view = new DataView(data.buffer, data.byteOffset, data.byteLength),