By default, pandoc will download media referenced from any
<img>, <audio>,
<video> or <source> element
present in the generated EPUB, and include it in the EPUB container,
yielding a completely self-contained EPUB. If you want to link to
external media resources instead, use raw HTML in your source and add
data-external="1" to the tag with the src
attribute. For example:
<audio controls="1">
<source src="https://example.com/music/toccata.mp3"
data-external="1" type="audio/mpeg">
</source>
</audio>If the input format already is HTML then
data-external="1" will work as expected for
<img> elements. Similarly, for Markdown, external
images can be declared with {external=1}. Note
that this only works for images; the other media elements have no native
representation in pandoc’s AST and require the use of raw HTML.