[mythtv-users] Digital Content with ICT = Image Constraint Tokens for HDCP

Robert McNamara robert.mcnamara at gmail.com
Tue Jul 28 14:24:05 UTC 2009

On Tue, Jul 28, 2009 at 2:15 AM, Tortise<tortise at paradise.net.nz> wrote:
> Hi Robert et al
> While the ICT is a media component it seems to me that it is a digital component that is a part of the recording and not the disc
> itself.  If it is the disc and outside the digital content recording, then in what way is it the disc, particularly DVD's?

Read the wikipedia article on AACS.  ICT is a part of AACS, and exists
at a lower level than the file structure or a flag in the raw video

> It has been suggested to me by a well known TV manufacturer that the ICT / affected media extends to broadcast signals including
> some satellite content and in time will also apply to our Terrestrial Freeview service.

Whomever suggested that was mistaken.  For specifics on why, read the
AACS article referenced above and note how it is tailored for physical
media.  I suspect this is a case of fear-mongering (on their part)
until someone can actually provide *some* type of reference.  While I
fully accept that it is possible to embed metadata in a transport
stream to trigger scaling down of the resolution, it will never be the
ICT (which is unique to AACS).  It is also not going to be something
that ever happens in myth (as code would need to be written to
actually use it).  From a quick google, I don't see anything besides
rumormongering by users, and not a single statement of fact.

> With reference to http://en.wikipedia.org/wiki/Image_Constraint_Token it seems a digital chain exists for all compliant equipment I
> presume to rubber stamp the tokens as they pass, it would seem the whole chain length, and back again, otherwise how would the
> source know whether to send up SD or HD content?

Yes, the ICT relies on HDCP, but no special mechanism of its own.
HDCP assures that the display path is protected, ICT triggers
downsizing if it is not.


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