The standard HTML template for video in Asset fields looks like this:
<iframe width="100%" height="100%" scrolling="no" allowfullscreen="true" frameborder="0" src="{stampvalue-config:baseaddress}dmm3bwsv3/embedplayer/play.aspx?accesskey={stampvalue-access:accesskey}&aid={stampvalue-asset:assetid}&autostart=0&width=auto&height=auto&videoquality=video{stampvalue-selected:quality}&fs=1" style="" siloid="{stampvalue-asset:assetsiloid}"></iframe>
What this does is it uses an iframe with a source to the connected Digizuite. This source returns an HTML section which embeds the Digizuite video player with a poster and source.
This means that Video is streamed directly from Digizuite. The reasoning behind this, is that video potentially can take up a lot of disk space and hence we do not want to cache it in the Sitecore server (as we do with other asset types).
Furthermore, Digizuite utilizes a video player called Flowplayer. This is an extension built on-top of the standard HTML5 video player. The main reason for this is it has the same styling across all browsers.
Using the standard HTML5 video player
The HTML template can also be customized to use the standard HTML5 video player if that is preferred. An example of such a template could look like this:
<div style="width:640px; height:360px;">
<video poster="{stampvalue-config:baseaddress}dmm3bwsv3/{stampvalue-asset:assetid}_2_11_1_11_0_{stampvalue-access:accesskey}_False.jpg" controls="controls" style="width:100%; height:100%;">
<source type="video/mp4" src="{stampvalue-config:baseaddress}dmm3bwsv3/{stampvalue-asset:assetid}_{stampvalue-selected:quality}_{stampvalue-config:destinationid}_1_11_0_{stampvalue-access:accesskey}_False.mp4">
</video>
</div>
This uses the standard HTML5 video player with direct streaming from Digizuite. This can of course be modified with styling as needed.
Custom video playback through API (code behind)
The video streaming URL is retrieved from the API, see this guide DFS 10.4.0 - 4 Accessing metadata through API, and using this a custom video player is constructable.