confirmed that this is indeed the first 10241 (we went off by one with
byte range 0-10240) of the full, playing mp4, so they probably
reencoded or something
u"description":u"This is a test case for youtube-dl.\nFor more information, see github.com/rg3/youtube-dl\nTest chars: \u2605\"'\u5e78 / \\\u00e4\u21ad\U0001d550",