Mailing List Archive

The use of CRIDs in MHEG and EIT streams
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@openmedia.co.nz
website - http://www.openmedia.co.nz
Re: The use of CRIDs in MHEG and EIT streams [ In reply to ]
On 1 May 2010 10:33, Steven Ellis <steven@openmedia.co.nz> wrote:
> 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

From the data I've seen, they are only using CRIDs with scheme
authority (SA) and the event identifier (EID). I've not see any
instance identifiers in the data. As for how they are mapped, from
what I can tell, they are just unique ids created by the SA. Since
each channel has it's own SA, there is no correlation of encoding
schema. Thankfully, four channels share the same SA (tvnz.co.nz,
1,2,6, and 7). So as long as the same show stays on the same SA, you
shouldn't get duplicates. However, if the same show appeared on a
different SA, it would be issued another EID by that SA. And they are
completely different in their conventions too.

Mythtv also has duplicate checking on title/description, but I'm
unaware how well that works without other metadata present. I've
written more code last night that I hope to finish today. It adds
dd_progid for the series/show ID and a master file for series
containing categories metadata.

sV

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