Avalon provides a mechanism for tracking the absolute locations of master/mezzanine and derivative files. The URLs it generates are not necessarily actionable, but are designed to give an administrator the ability to locate a particular file unambiguously. Avalon takes its best guess at how to build sensible URLs, but can be configured for better specificity and other modes of access.
Master Files
Master files (the original, pre-transcoding, uploaded files) are stored in the path specified by the matterhorn.media_path key in config/avalon.yml, and (optionally) moved elsewhere after processing. The location of the master file is turned into a URL via the following steps:
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That would cause Avalon to link to the master file at /var/avalon/masterfiles/dropbox/my_collection/my_video.mp4 as http://masterfiles.northwestern.edu/dropbox/my_collection/my_video.mp4.
Derivatives
Derivatives (transcoded streaming files) are handled differently, since, unlike master files, there's no guarantee that the Avalon server has access to or knowledge of the locations where streaming content is stored. Instead of having to mirror Matterhorn's streaming configuration within Avalon, Avalon simply requests an avalon.stream_base property from Matterhorn. This property can be found in Matterhorn's etc/load/org.opencastproject.organization-mh_default_org.cfg file. By default, the property is a file:// URL prefix pointing to the directory where derivatives are stored:
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