“When I finish the recording for my new CD I would like to have the CD copy protected. What do I do?”
For standard audio discs the current copy protection scheme is known as SCMS. There are two bits of subcode data associated with this. The first is the Copyright bit, and the second is the Copy Status bit. The first bit determines whether the material is copyrighted at all. If it is not set the material can be freely copied and the second bit is ignored. The second bit is designed to define whether the recording is an original or a copy. If it is set high the recording cannot be copied on any device equipped with SCMS.
Here’s how it’s supposed to work. Most commercial CD’s are made with the Copyright bit on and the Status bit to original. If someone makes a digital copy of the CD on an SCMS equipped device the copy will be made with both the Copyright bit on and the Status bit set to “copy,” which signifies that the recording is a copy of an original. That copy then cannot be used as a source for further copying on any machines equipped with SCMS.
Most of the pro CD authoring software packages allow you to set the status of the copy protection bits. But (and this is the crux of the issue) there are so many ways to beat SCMS copy protection today it’s almost not worth the trouble. SCMS is only checked on S/PDIF transfers (which does account for most consumer machines). It is ignored on AES transfers and by hardware that makes image copies of CD’s. It is, however, picked up by consumer CD duplicators (such as the popular Phillips unit) and all consumer DAT machines, so if your goal is to make it difficult for consumers to copy your material, SCMS is still marginally effective. And since it’s the only game in town it’s all you’ve got. Other emerging optical formats such as DVD employ much more sophisticated (read: harder to beat) schemes for copy protection.