On Friday 15 Jun 2007, Jonathan McDowell wrote:
> On 12/06/07, Alex Stansfield <[EMAIL PROTECTED]> wrote:
> > If anyone knows any more about how the system works or has the DTG
> > specification (can't see it on their website) please let me know.
>
> MythTV seems to have added support:
>
> http://svn.mythtv.org/trac/ticket/2811

Hmmm. I worked out the scheme using dvbsnoop last night, then decided it 
couldn't possibly be so simple. Seems I was right after all...

The data is transmitted in the EIT. Each entry has zero, 1 or 2 Content 
Identifier Descriptors, with table ID 0x76. The format of this descriptor 
seems to be:

Descriptor tag, 8 bits (always 0x76)
Descriptor length, 8 bits
crid_type, 6 bits
crid_location, 2 bits (always seems to be 00)
crid_len, 8 bits
crid_data, crid_len bytes.

If crid_type = 0x31 then crid_data contains the program ID, which I think 
is supposed to uniquely identify the programme irrespective of repeats 
etc.

If crid_type = 0x32 then crid_data contains the series ID, which should be 
the same across all episodes of a series. The series ID is sometimes 
omitted if the programme is a one-off.

I'm not sure just how unique these identifiers are supposed to be; the 
series identifiers are generally 5-digit numbers or 6-character alpha 
strings preceded by "/", while the program ID seems to have the episode 
number appended.

On Sandy Heath I only see this data on the BBC, "4" and sky channels, not 
ITV.

Dave

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