output encoding parameters, which are expressed by a
base64-encoded representation of a binary block. The first 16 bytes of
this binary block are used as master key, the following 14 bytes are
used as master salt.
</p></dd>
</dl>

<a name="subfile"></a>
<h2 class="section"><a href="ffmpeg-protocols.html#toc-subfile">3.33 subfile</a></h2>

<p>Virtually extract a segment of a file or another stream.
The underlying stream must be seekable.
</p>
<p>Accepted options:
</p><dl compact="compact">
<dt>&lsquo;<samp>s