Analog hole
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The analog hole is a fundamental vulnerability in copy prevention schemes for digital content which is intended to be played back using analog means. When the information is converted to analog form, there are no restrictions on the resulting analog signal, and the content can be captured back into digital form with no restrictions.
However, this kind of reproduction is not a digital copy, and therefore will have flaws, the magnitude of the flaws depending on the quality of reproduction methods used. For example: bootleg movies may have poor audio, or highly washed-out video. In this manner, the copy prevention can be circumvented for types of material whose value is aesthetic, and does not depend on its exact digital duplication. Software cannot be copied in this manner, for example.
Regardless of the digital or software copy control mechanisms, if music can be played on speakers, it can also be recorded. Just as text can be printed or displayed, it can also be scanned and recognized.
A few methods have attempted to "plug" the analog hole, and have met with limited success. Macrovision attempts to defeat VCRs 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 happen when viewing the original video as well.