[mythtvnz] The use of CRIDs in MHEG and EIT streams

[Steven Ellis]

Thought it would be worth while splitting the technical discussion of the CRID data from the current grabber thread until we have the details worked out.

I've managed to dig out the following references

CRID format
CRIDs carried in SI may be defined in such a way that the Scheme and Authority parts are carried once only if they are common to a group of CRIDs. However the format for CRIDs passed across the MHEG PVR API in any of the following Resident Program calls shall include the Scheme and Authority parts in all cases.
A CRID that does not include an instance identifier shall be in the format:
Scheme + Authority + Unique Identifier
A CRID that includes an Instance Identifier shall be in the format:
Scheme + Authority + Unique Identifier + # + Instance Identifier

Examples of CRIDs with and without Instance Identifiers follow:
	crid://company.tv/123df5
	crid://broadcaster.com/hef5w#e1
As specified by [DTG DTR] CRIDs carried in SI are case insensitive. However, MHEG-5 operations on strings are case sensitive. So:
• the following Resident Programs shall be case preserving • operations relative to broadcast SI shall be case insensitive


Basically the myFreeview PVRs can book programs by either series ID or episode. The EIT stream on DTH also contains these crid fields so the PVR can match the booking to the correct program.

One other benefit is that if they start broadcasting EIT Actual then the PVR should realise when a program is delayed and re-schedule accordingly.

You can find the TV Anytime reference on CRIDs here
 * http://www.rfc-archive.org/getrfc.php?rfc=4078

Haven't found any reference on how a CRID is mapped to a particular show, of if it is program unique or program+network unique.

Steve


Steven Ellis - Technical Director
OpenMedia Limited
email   - steven at openmedia.co.nz
website - http://www.openmedia.co.nz

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