Audio and video media are becoming an increasingly important part of libraries’ online holdings. Distribution may need to be limited to in-library devices or authorized users. The issue isn’t basically different from written documents and images, but it’s more technically complicated, and rights holders are often more sensitive about letting AV get into unauthorized hands.
One approach is to outsource the collection to a site that will manage and deliver content. This is attractive to libraries that don’t have their own IT departments — which is to say the large majority. For example, iTunes U allows course material to be distributed through Apple and optionally restricted to authorized viewers or listeners. The downside is that non-Apple mobile devices are less well supported; the service is there to sell iPads. An platform-neutral alternative is MediaCore. Neither one supports DRM; in some ways that’s good, though it may be a deal breaker.
A simpler alternative is to put the files behind a password-protected server and let authorized users download them, just as they’d download any other restricted files. If the stakeholders providing the materials think this is enough protection, it’s a straightforward approach. With HTML5, it’s easy to provide a web page on which the content will play on nearly all current browsers. It’s important to provide the material in a couple of different formats to maximize compatibility. For audio this should include Ogg Vorbis as well as either MP3 or AAC. For video you should have MP4/H.264 and Ogg Theora, and possibly WebM as well.
Having a player page gives the library the advantage of branding; most users will play the audio or video on that page and will know that the library is providing it. However, it does nothing to stop users from grabbing the content and redistributing it. The URL is right in the page and can be downloaded directly. It’s a question of how important this is.
Beyond that there are solutions using dedicated server software. This allows true streaming with on-the-fly bitrate adjustment, a slightly higher (but still weak) barrier to copying, and closer control over the presentation. Only a few libraries are in a position to offer that, so I won’t get into it here.
Much of the complication comes from having to deal with handheld and tablet devices. Reaching all desktop browsers isn’t too hard, but getting content to play on iOS and Android can get tricky. The world of streaming protocols is very fragmented (here’s a technical discussion if you’re interested), and getting streaming to play on all major devices can be a pain.