TechBlog from Sewell

High-Bandwith Digital Content Protection. HDCP is an encryption method that is used in High Definition video applications that was designed by Intel, and has had the support of the movie industry, but there are a couple of things you might want to know about it.

What it does. Part of why movie studios are supporting HDCP is because it is a deterrant to piracy of movies. But that isn’t exactly the primary role of the HDCP encryption…the encryption guarantees the signal quality. Basically the ’sending end’ encrypts the signal, and creates a verification code. On the ‘recieving end’ it checks the verification code, then decrypts the signal, so you know you are displaying the exact signal that was sent. The real way that HDCP protects against piracy is implemented by the device manufacturers. For example, if I wanted to make my own Plasma TV to hook up to an HD DVD player with HDMI, I would apply for an HDCP license and I would have to prove that my TV does not allow piracy, and ‘effectively frustrates’ piracy attempts. So it’s really not the encryption that prevents piracy, it is my TV, but I need to so that I can decrypt the signal. Clear as mud?

What uses HDCP. HDCP can only be implemented over a digital interface, which currently, in home theater means HDMI or DVI. Composite, S-Video, Component, and RGB (DB15 or DSUB) connections are all analog connections and will not work with digital encryption.

Here’s the catch. Both DVI and HDMI acually use the same video signals, (HDMI supports audio as well, DVI does not) so you can connect either to either with DVI to HDMI cables or DVI to HDMI converters that should work flawlessly… Except that DVI was released before HDCP, so not all DVI devices suport HDCP. (All HDMI devices do) So if you have an older DVI TV that Doesn’t suport HDCP, and a DVD player that does, even though it “Should work” the TV will be recieving a scrambled signal, and it obviously won’t display properly, if at all. Manufacturers do have the option of displaying a toned down version of the signal (480p for example) But it would depend on them to build that into their units.

Catches. The other problem is if you don’t have a digital connection at all. An HDTV with only Component video, or the VGA style RGB connection can’t display HDCP protected content. (so no need running out to buy a blue-ray) Even though those connections can support HD signals from OTA broadcasts, game consoles or a cable/satelite box, movie makers aren’t realy keen on releasing unprotected HD videos, so your player might output an analog signal, but only at 480. sorry

We have a DVI to Component cable that looks deceptively like a solution to the problem. Unfortunately it is not. The cable is designed for computer graphics cards that specifically output an analog TV compatible signal. (It probably won’t even fit the connection on your cable box)

In a couple of years, this will all get more standardized and iron itself out. But for now there are still a few wrinkles and creases we just have to deal with. But that’s technology.

This entry was posted on Wednesday, January 11th, 2006 at 7:00 am and is filed under DVI, HDMI, Video. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.