Image and Media Delivery

The DLCS can deliver images, audio and video from a high-availability, load-balanced service that can scale to any volume of content, and to any volume of user traffic. The Image and Media delivery service supports the IIIF Image API and will support the upcoming IIIF A/V specification.

Benefits of the DLCS Media Delivery Service

  1. support for open APIs via the IIIF Image API.
  2. fast thumbnail delivery via pre-generated static thumbnail images.
  3. fast tiled ‘deepzoom’ image viewing in a wide range of compatible clients.
  4. fully load-balanced and cached architecture.

Technical Overview


For information about how images and media get ingested into the DLCS see: Ingest Architecture

This service handles all types of IIIF image or media requests with separate logic pipelines for graphical images and audio/video items.

Image Requests

Graphical image requests that do not require authentication are cached in front of the application. Image delivery makes use of sophisticated caching where the ‘long tail’ of items that are infrequently viewed are only moved to fast storage when required.

For items which do require authentication, the delivery service implements the IIIF Auth spec using info.json requests. Once authenticated, or for images that do not require auth, initial requests for images are analysed and may result in being quickly served from existing image derivatives, such as pre-generated static thumbnails.  Alternatively, the requests will be served from a load-balanced and scalable cluster of IIIF Image API compatible image servers direct from an optimised JPEG2000 asset which has been copied onto a filesystem cache for speed.

Audio/Video Requests

Audio/video requests are handled slightly differently, with open items handled directly from Amazon S3 via a redirect, and closed items proxied from Amazon S3 once the request has been authenticated.