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Content reference identifier

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CRID redirects here. CRID may also refer to a Current Rail Indicator Device, a safety device which indicates the presence of third rail power; cf. [1].

Overview

A Content Reference Identifier or CRID is a concept from the standardization work done by the TV-Anytime forum. It is or closely matches the concept of the Uniform Resource Locator, or URL, as used on the World-Wide Web:

A unit of content, in a broadcast stream, can be referred to by its globally unique CRID in the same way that a webpage can be referred to by its globally unique URL on the web.

The concept of CRID permits to reference contents unambiguously, regardless of their location, i.e., without knowing specific broadcast information (time, date and channel) or how to obtain them through a network, for instance, by means of a streaming service or by downloading a file from an Internet server.

The receiver must be able to resolve these unambiguous references, i.e., translate them into specific data that will allow it to obtain the location of that content in order to acquire it. This makes it possible for recording processes to take place without knowing that information, and even without knowing beforehand the duration of the content to be recorded: a complete series by a simple click, a program that has not been scheduled yet, a set of programs grouped by a specific criterion…

This framework allows for the separation between the reference to a given content (the CRID) and the necessary information to acquire it, which is called a “locator”. Each CRID may lead to one or more locators which will represent different copies of the same content. They may be identical copies broadcast in different channels or dates, or cost different prices. They may also be distinct copies with different technical parameters such as format or quality.

It may also be the case that the resolution process of a CRID provides another CRID as a result (for example, its reference in a different network, where it has an alternative identifier assigned by a different operator) or a set of CRIDs (for instance, if the original CRID represents a TV series, in which case the resolution process would result in the list of CRIDs representing each episode).

From the above it is obvious that, provided that a given content can belong to many groups (each possibly defined by distinctive qualities), it is possible that many CRIDs carry the same content. That is, several CRIDs may be resolved into the same locator.

A CRID is not exactly a universal, unique and exclusive identifier for a given content. It is closely related to the authority that creates it, to the resolution service provider, and to the content provider in such a way that the same content may have different CRIDs depending on the field in which they are used (for example, a different one for each television operator that has the rights to broadcast the content).


Format

A CRID is specified much like URLs. In fact, a CRID is a so-called URI. Typically, the content owner will use their DNS-names in a combination with a product-specific name to create globally unique CRIDs. As an example, let's assume that BBC wanted to make a CRID for the Olympics in China. It may have looked something like this 

crid://bbc.co.uk/olympics/2008/

Then, to refer to a specific event - such as the women's shot-put final - they could have used the following inside their metadata. 

crid://bbc.co.uk/olympics/2008/final/shotput/women

Currently,[when?] four types of CRIDs are playing a major role in some unidirectional television networks: programme CRID, series CRID, group CRID, and recommendation CRID. One of the most important applications of CRIDs is the so-called series link recording function (SL) of modern digital video recorders (DVR, PVR).

In web casting

To make the CRID even more globally available the IETF will publish a request for comments specifying the use of the CRID over the web. This will allow consumer devices to hook up to content provider servers, much like current browsers look up webservers, requesting content by CRID.

In May 2005, an Informational RFC, No 4078, was published as the start of this work.

The long-term goal is that CRIDs should be available for use by cell phones, PDAs, digital TV receivers and other consumer devices for fetching content, either from a broadcast stream or over IP-based networks.

References

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