Encryption and Copy-Protection
Before we get into defining what encryption and copy-protection are we must point out one thing that is perhaps misunderstood the most: copy-protection and encryption are not the same thing! With that cleared up, let’s dig a little deeper.
Encryption is actually a pretty simple concept to understand. When a cable company provides a video stream they can basically do it in one of two ways. They can encrypt it, or leave it unencrypted. Channels that are left unencrypted by the cable company are called ClearQAM channels. You can use a ClearQAM tuner in your television or home theater computer to watch these channels without the need of a set-top-box from the cable company. Every cable company makes different decisions as to what they want to encrypt. Generally speaking, the channels that you can get for free over the air are left unencrypted, but most of the rest of the cable channels are encrypted.
Copy-protection is completely separate, and different, than encryption. Copy-protection is a strategy employed by the content providers to attempt to prevent their customers from illegally sharing the content. The protection level is determined by the Copy Control Information bit within the video stream. The first important thing to know is that this flag can be set on individual programs. This means that it is possible that two different programs on the same channel could be using different levels of copy-protection. There are six different values that can be sent using the CCI bit, but only two are commonly used. Copy Freely (0×00) and Copy Once (0×02.) Copy Freely is exactly how it sounds. Basically it means that there aren’t any copy restrictions on the program being streamed. You can record it to your DVR or HTPC and you can copy that recording to other devices. Copy Once is a little different than how it sounds. When a show is marked Copy Once you can record it to your DVR or HTPC. That initial recording is considered your “one copy” though. You cannot copy it to any other devices. If you have a Windows Media Center-based home theater PC you do have one other option for viewing that Copy Once content on other televisions within your home. Any Media Center Extender (like an XBOX 360) that is paired with your Media Center computer can also view all of it’s copy-protected content.
Copy-Protection and CableCARD
Many people seem to think that all content that comes via CableCARD is 100% copy-protected 100% of the time just because its coming over CableCARD. That is completely not true. What we need to keep in mind is that CableCARD is just a replacement for having a set-top-box. This confusion is justified though. When the ATI Digital Cable tuners were first introduced the firmware didn’t properly read the copy-protection bit, so instead they just marked everything as copy-once. The new card in town, the Ceton InfiniTV 4, properly handles the copy-protection bit, and therefore it only marks recordings as copy-once if the bit tells it to.
Hopefully that clears up what can be a pretty confusing issue. Leave a comment if we left something out, or if you think we got something wrong.