<p>This might be a silly question:</p>

<ul>
<li>Does HTTP ever use the User Datagram Protocol? </li>
</ul>

<p><strong>For example:</strong> </p>

<blockquote>
  <p>If one is streaming MP3 or video  using HTTP,  does it internally use UDP for transport?</p>
</blockquote>

Typically, no.
Streaming is seldom used over HTTP itself, and HTTP is seldom run over UDP. See, however,
RTP
.
For something as your example (in the comment), you're not showing a protocol for the resource. If that protocol were to be HTTP, then I wouldn't call the access "streaming"; even if it in some sense of the word is since it's sending a (possibly large) resource serially over a network. Typically, the resource will be saved to local disk before being played back, so the network transfer is not what's usually meant by "streaming".
As commenters have pointed out, though, it's certainly possible to really stream over HTTP, and that's done by some.