I don't know if this is the best solution for your problem but I'd gone with:
Code:
<script>
function ChangeVideo(src1, src2)
{
document.getElementById('mp4').src = src1;
document.getElementById('webm').src = src2;
}
</script>
<video id="video" class="video-js vjs-default-skin" controls width="960" height="544" autoplay="true" preload="auto" data-setup="{}">
<source src="#" id="mp4" type='video/mp4'>
<source src="#" id="webm" type='video/webm'>
</video>
<a href="#null" onclick="ChangeVideo('source-to-the-mp4', 'source-to-the-webm');">Antibioclic</a>
If you're not too sure about what functions does it's something like this:
Code:
<a href="#null" onclick="document.getElementById('mp4').src = 'source-to-the-mp4'; document.getElementById('webm').src = 'source-to-the-webm';">Antibioclic</a>
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