This is Project Baird.

Collating a list of all services provided by an over-the-air broadcaster

This information is out of date an incomplete

  1. Construct a TVDNS or RadioDNS domain name for the current service

  2. Query DNS for the xrd application

  3. Download the manifest XRD

  4. Each linked feed relates to a service; those which are related to a known over-the-air service can be added immediately to a list of broadcaster’s services

  5. For the remainder, download each feed.

  6. For each feed, examine the atom:link entries which are children of the root atom:feed element. If:

    • rel="alternate http://projectbaird.com/ns/demand" is specified, or
    • rel="alternate http://projectbaird.com/ns/linear" is specified; and if
    • the type attribute contains a MIME type supported by the device; and if
    • (if present) the le:media attribute matches the device type and constraints; then
    • add the service described by the feed to the list of broadcaster’s services.
  7. If no match was made by step 6, then if an atom:entry is present which contains an atom:link element where:

    • rel="alternate http://projectbaird.com/ns/demand" is specified, or
    • rel="alternate http://projectbaird.com/ns/linear" is specified; and if
    • the type attribute contains a MIME type supported by the device; and if
    • (if present) the le:media attribute matches the device type and constraints; then
    • add the service described by the feed to the list of broadcaster’s services.
  8. Present the list to the user

Notes

  1. Broadcaster prerequisites:
    • TVDNS domains for the services it broadcasts are configured and registered with the TVDNS administrative body or hierarchical parent (e.g., platform operator), as appropriate
    • SRV and TXT records for the feed manifest have been published
    • Properly-populated feed manifest and service feeds are available
  2. See http://projectbaird.com/ns/ for a description of element, attribute and link relation extensions
  3. See the device profiles for information on anticipated content type support on different devices
  4. See Atom Link Extensions for information on the le:media attribute.
  5. Media queries are defined by the Atom Link Extensions specification to match those specified by CSS3
  6. The collated list of services will in many cases include a combination of linear-only, demand-only and hybrid services, in part depending upon which might be available over-the-air.

Example scenario

A broadcaster has a set of linear and on-demand services. Its on-demand services are delivered solely via IP and offers catch-up programming, as well as some exclusive content. Of the linear services, only a subset may be available to a user of a given platform.

Thus, if the broadcaster has seven linear channels, but the user can only access four of them over-the-air, then they would be able to access at least some of the programmes from the remaining three provided they were described as being available for either linear or on-demand access via IP. If the feeds for any of those three channels contained no information relating either the service as a whole or any of the programmes it describes, the service would not appear in the list presented to the user.