Analog Hole - Overview

Overview

Although the technology for creating digital recordings from analog sources has existed for some time, it was not necessarily viewed as a "hole" until the widespread deployment of DRM in the late 1990s. It should be pointed out that this kind of duplication is not a direct digital copy, and therefore has flaws, the magnitude of which depends on the nature of the reproduction methods used. This kind of reproduction is, in many ways, similar to the initial digitization of any analog medium or performance, with all the pitfalls and benefits of such digitization. For example, bootleg films may have poor audio, or highly washed-out video. At a minimum, copy protection can be circumvented for types of material whose value is aesthetic, and does not depend on its exact digital duplication. In general, performing a digital-to-analog conversion followed by an analog-to-digital conversion results in the addition of noise in an information-theoretic sense relative to the original digital signal. This noise can be measured and quantified. Naturally, the use of high quality conversion equipment reduces the amount of noise added, to the point where such noise is essentially imperceptible to the human senses.

Regardless of any digital or software copy control mechanisms, if sound can be heard by an ear, it can also be recorded by a microphone. And if images (static images or video/film), including text, can be seen by the eye, it can also be recorded by a camera. In the case of text the image can be converted back to text using optical character recognition.

In 2002 and 2003, the U.S. motion picture industry publicly discussed the possibility of legislation to "close the analog hole" — most likely through regulation of digital recording devices, limiting their ability to record analog video signals that appear to be commercial audiovisual works. These proposals are discussed in the Content Protection Status Report, Consumer Broadband and Digital Television Promotion Act, and Analog Reconversion Discussion Group. Inventors of digital watermark technologies were particularly interested in this possibility because of the prospect that recording devices could be required to screen inputs for the presence of a particular watermark (and hence, presumably, their manufacturers would need to pay a patent royalty to the watermark's inventor).

The motion picture industry has also pursued several private-sector approaches to eliminating the analog hole; these might be implemented without additional legislation.

• Analog signals can be degraded in ways that interfere with or confuse some recording devices. For example, Macrovision attempts to defeat recording by VCRs and DVD players by outputting a deliberately distorted signal, crippling the automatic gain control for video, causing the brightness to fluctuate wildly. While this is only supposed to happen to copies, it may, as an inadvertent side-effect, happen when viewing the original video as well. Some vendors claim to have developed equivalent techniques for preventing recording by video capture cards in personal computers. Devices exist, however, to counteract this measure.
• Manufacturers of recording devices can be required to screen analog inputs for watermarks (or Macrovision or DCS Copy Protection or CGMS-A) and limit recording as a condition of private contracts. For example, a manufacturer who licenses patents or trade secrets associated with a particular DRM scheme might also be obliged as a purely contractual matter to add recording limitations to digital recording products.
• Manufacturers of certain playback devices such as set-top boxes can be required, as a condition of private contracts, to allow publishers or broadcasters to disable analog outputs entirely, or to degrade the analog output quality, when particular programming is displayed. This capability is one example of selectable output control. A broadcaster could then prevent all recording of a broadcast program by indicating that compliant receiving devices should refuse to output it through analog outputs at all.

In theory, it is possible to bypass all these measures by constructing a player that creates a copy of every frame and sound it plays. Although this is not within the capability of most people, many bootleggers simply record the video being displayed with a video camera or use recording and playing devices that are not designed to use the protection measures. In fact, the Motion Picture Association of America has recommended use of a camcorder as an alternative to circumventing the Content Scrambling System on DVDs.