pandoc does not convert poster images into data-URIs when using --self-contained

commandline use

$ ~/.cabal/bin/pandoc --version
pandoc 1.12.3.3


$ ~/.cabal/bin/pandoc -w dzslides --standalone --self-contained ~/tmp/pandoc-poster-image-test.md > ~/tmp/pandoc-poster-image-test.html

pandoc-poster-image-test-expected.html

<section id="slide-1" class="slide level1" aria-selected="true">
  <h1>Slide 1</h1>
  <video preload="auto" loop="loop" src="data:video/mp4;base64,AAAA...AAA4" type="video/mp4" poster="data:image/png;base64,iVBOR...YII=" width="320" height="320"></video>
</section>
<section id="slide-2" class="slide level1">
  <h1>Slide 2</h1>
  <figure>
    <img src="data:image/png;base64,iVBOR...YII=">
  </figure>
</section>

pandoc-poster-image-test-html.png

pandoc-poster-image-test.md

Slide 1

Slide 2