Content reference identifier
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 referencing 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 capable of resolving these unambiguous references, i.e. of translating 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”.
Typically, the content creator, the broadcaster or a third party will use their DNS-names in a combination with a product-specific name to create globally unique CRIDs.
Then, to refer to a specific event – such as the women's shot-put final – they could have used the following inside their metadata.
The locators' format, as established in TV-Anytime, is quite generic and simple, and corresponds to: The first part of the locator’s format (the transport mechanism) must be a string of characters that is unique for each mechanism (transport stream, local file, HTTP Internet access…).
This procedure involves some information elements, among which we find two structures named resolving authority record (RAR) and ContentReferencingTable, respectively.
For example, in the record of the figure (expressed by means of a XML structure, according to the XML Schema defined in the TV-Anytime) there is an authority called “tve.es”, whose resolution service provider is the entity “rtve.es”, available on the URL "http://tva.rtve.es/locres/tve", which means there is resolution information in that URL.
Once a RAR record corresponding to that authority is found, the receiver will know, by referring to the URL field, where to access (or, in this case, where to listen) to obtain the resolution information.
The information that will receive through that access point will consist of a message for each of the consulted CRIDs (for example, a
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 networks.
