Edit /boonex/modules/html5av/classes/BxH5avModule.php and ...

1. Look for (around line 89):

$sOverride = '
    <video controls preload="auto" autobuffer ' . $sAutoPlay . $sPoster . ' style="width:100%; height:' . getSettingValue('video', 'player_height') . 'px;" id="' . $sId . '">
        ' . $sSourceWebm . '
        <source src="' . BX_DOL_URL_ROOT . "flash/modules/video/get_file.php?id=" . $iFileId . "&ext=m4v&token=" . $sToken . '" />

Replace the whole bit with this:

$sOverride = '
    <link href="//vjs.zencdn.net/4.12/video-js.css" rel="stylesheet">
    <script src="//vjs.zencdn.net/4.12/video.js"></script>

    <video class="video-js vjs-default-skin vjs-big-play-centered" data-setup=\'{}\' width="100%" height="' . getSettingValue('video', 'player_height') . 'px" controls preload="auto" autobuffer ' . $sAutoPlay . $sPoster . ' id="' . $sId . '">
        ' . $sSourceWebm . '
        <source type=\'video/mp4\' src="' . BX_DOL_URL_ROOT . "flash/modules/video/get_file.php?id=" . $iFileId . "&ext=m4v&token=" . $sToken . '" />

---

2. Look for (around line 230):

$sOverride = '
    <audio controls ' . $sAutoPlay . ' preload="auto" autobuffer style="width:100%" id="' . $sId . '">

Replace the whole bit with this:

$sOverride = '
    <link href="//vjs.zencdn.net/4.12/video-js.css" rel="stylesheet">
    <script src="//vjs.zencdn.net/4.12/video.js"></script>

    <audio class="video-js vjs-default-skin vjs-big-play-centered" data-setup=\'{}\' width="100%" controls ' . $sAutoPlay . ' preload="auto" autobuffer style="width:100%" id="' . $sId . '">

---

3. Look for (around line 344):

$sOverride = '
    <video controls preload="auto" autobuffer id="' . $sId . '">
        ' . $sSourceWebm . '
        <source src="' . BX_DOL_URL_ROOT . "flash/modules/video_comments/get_file.php?id=" . $iFileId . "&ext=m4v&token=" . $sToken . '" />

Replace the whole bit with this:

$sOverride = '
    <link href="//vjs.zencdn.net/4.12/video-js.css" rel="stylesheet">
    <script src="//vjs.zencdn.net/4.12/video.js"></script>

    <video class="video-js vjs-default-skin vjs-big-play-centered" data-setup=\'{}\' width="100%" controls preload="auto" autobuffer id="' . $sId . '">
        ' . $sSourceWebm . '
        <source type=\'video/mp4\' src="' . BX_DOL_URL_ROOT . "flash/modules/video_comments/get_file.php?id=" . $iFileId . "&ext=m4v&token=" . $sToken . '" />

---

That's it. Clear all cache and take a look.