Originally Posted by km
I see CCI defined in the DTCP spec which was inherited by HDCP, for the firewire. It's this flag that I can examine in the 3412's D6 diagnostic screen.
Whats not clear to me is how this directly relates to the OTA broadcast signal. Is there actually a CCI flag defined in 8VSB? I thought that there was a controversial "broadcast flag" for OTA digital broadcasts with which Congress was considering mandating compliance. Is the CCI flag for HDCP just a reflection of that flag?
I also wonder if Comcast even receives the local OTA digital signals via 8VSB, which is an RF modulation standard. I would think they would get a digital feed more directly.
I've been trying to contact engineering both at Comcast and the originating local stations to ask if they are actually setting CCI=2 on purpose. No responses yet. In my area its only the ABC and NBC affiliates that have CCI=2. CBS, FOX, TBS, WB as well as the premium cable channels are all at CCI=0.
The CCI flag is set in the MPEG2 encoding process, and really has nothing to do with either 8VSB or QAM. Since Comcast isn't encoding OTA HD, (it is already at MPEG2, the 8VSB or QAM is just the delivery method), they shouldn't be the ones to set the flag. There is an eMedialive article that talks a little about CCI. Unfortunately, being a newbie posting on this forum, I can't include the URL (I haven't had 5 posts yet.... ) However, if you go to the eMedialive site and search on CCI, you should get a hit on an article called "Changing of the Guard".
The pertinent portion in this discussion can be found on page 3, under the heading Protection in the Real WorldOnce you do decide that your content should be protected, the CCI flag must be added to the MPEG transport stream. Alas, the CCI flag can't be placed into a basic MPEG transport stream; it was created long before the HD copy protection standards were released. Fortunately, the creators of MPEG transport specification realized that they could not anticipate every possible future extension. Consequently, they set aside a special portion of the stream, called private data, where new features could be incorporated into the stream.
For example, the DTLA has defined a DTCP descriptor that is placed into this private data area. This descriptor contains the CCI flag and related info that source devices can use to detect if the stream is copy protected. The DTCP descriptor should be added to the MPEG transport stream when it is first created.
The article goes on to say that the flag could be set anywhere before it gets to the end user, but why would Comcast want to do that? It isn't their content, and they would need to buy another piece of equipment to insert it.
Getting an 8VSB signal off the air and transcoding, it is usually a whole lot cheaper than building a digital link from the studio to get it more directly. In the past decade or so, many cable companies have partnered with TV stations to get a direct link between the studio and the cable headend, BUT, it was usually built and optimized for the analog NTSC signal, as that was the signal that was most susceptible to interference. On the other hand, the links done most recently were probably designed and built so that both the analog and digital signals could be transported. I don't know what the deal is in your area, but where I am, in New England, the analog comes from a studio feed and the HD is received OTA and transcoded. The only exception I am aware of is one TV station that was waiting to get their DTV transmitter built and licensed, and built a digital link to the cable HE so they could at least get their HD signal in front of cable subscribers.