Mario Peshev

Theme Mentor is a cousin of the Theme-Check plugin getting deeper into the code analysis.
It’s using different approaches to monitor for common problems regarding theme reviews from the WordPress Theme Reviewers Team. It is prone to fault analysis, so use only as a reference for improving your code base even further.
Currently supported validations:
<ul>
<li>Mark all tags in template files</li>
<li>Mark all tags in template files</li>
<li>Warn about query_posts() usage</li>
<li>capital_P_dangit control (disallow any WordPress spelling other than WordPress as is – that is WORDPRESS and WordPress, ugh)</li>
<li>wp_deregister_script(‘jquery’) is forbidden</li>
<li>wp_dequeue_script(‘jquery’) is forbidden</li>
<li>prevent global $data; call as a common troublemaker (props @pippinsplugins)</li>
</ul>
header.php specific
<ul>
<li>Make sure that wp_head is before </li>
<li>Ensure that wp_title(…) is called within and tags</li>
</ul>
footer.php specific
<ul>
<li>Make sure that wp_footer is before </li>
</ul>

Theme Mentor

Theme Mentor is a cousin of the Theme-Check plugin getting deeper into the code analysis.

team-ok

Switch Video Quality adds a quality switch button to the native wordpress video player (mediaelement.js), that allows to choose between different resolutions (e.g., SD and HD) and/or formats (mp4, webm, ogv) of a self-hosted html5-compatible video. Additionally it provides an iframe embed code to let your viewers embed your video into their website (optional).
<h4>Features:</h4>
<ul>
<li>serve your videos in multiple qualities to let your viewers choose (just like youtube or vimeo)</li>
<li>upload your video files directly to the wordpress media library or use a separate web server to host your files (direct URLs have to be entered manually)</li>
<li>create a playlist when you have more than one video on a page (only one player needed). The playlist is placed below the player as a grid layout with thumbnails for each video</li>
<li>provide an automatically generated iframe embed code for each video</li>
<li>use subtitles for multiple languages</li>
<li>reorder playlist items with drag and drop</li>
<li>quality level labels show the video’s height value by default, but you can set custom ones easily</li>
<li>HD and 4K quality flags are added to the labels automatically</li>
<li>optionally show an info overlay in the player that contains title and duration information</li>
<li>turn on/off on a per-post basis</li>
<li>fully translatable (english and german language files already included)</li>
</ul>
<h4>How to use:</h4>
<ul>
<li>In the post editor, use the normal video shortcode (width and height set to your needs) to place the video player in your content area, like this: 
[video width=1024 height=576]</li>
<li>There are no other shortcode attributes necessary (actually even width and height aren’t necessary as they default to 640 x 480 px when they are omitted), but you may add a src and a poster attribute to ensure normal shortcode functionality when Switch Video Quality is not used or deactivated.</li>
<li>Select the checkbox Turn on/off to activate the plugin for the current post.</li>
<li>In the playlist item box enter some information about your video such as titles, names, locations, dates or an external link. This information will be displayed in the playlist and in the information overlay of the video player.</li>
<li>Upload a poster image or select one from the media library</li>
<li>Upload your videos with different resolutions and/or different formats (mp4, webm or ogv).</li>
<li>You can select multiple video files in the media library and add them to the current playlist item all at once.</li>
<li>The order of the files (quality levels) doesn’t matter as they will be sorted by their height value when they’re loaded into the player. The quality level that is closest to (but – to avoid upscaling – not smaller than) the player’s size will be loaded as default.</li>
<li>All video details (URL, label, duration) are inserted automatically, but you can change the default label text to whatever you like (e.g., low, medium, high)</li>
<li>If your video files are hosted on an external server, enter the URLs manually (the plugin will try to fill out the other fields automatically)</li>
<li>To add another playlist item, click on the plus icon at the top of the current playlist item box</li>
<li>To change the order of the playlist items, click on the playlist position number and drag and drop the box below or above another one.</li>
<li>When you click on the title of the box, this box gets expanded (content is shown) and all others will be collapsed. You can collapse all boxes by clicking on the title of an open one (makes rearranging of the boxes easier).</li>
<li>Empty a playlist item box by clicking on the rubber icon, remove the whole box completely by clicking on the X icon (not possible when there is only one box left)</li>
</ul>

Switch Video Quality

This plugin is simple and great. However it needs much work to make it greater and maybe part of Wordpress core.

Fantastic Plugin

Adds quality switch functionality and automatic embed code generation to the wordpress video player.

Theme Mentor vs Switch Video Quality