Reverse Spiral Dual Layer. A DVD which has two layers for data. The first layer reads from the inside of the disc to the outside of the disc, and the second reads back from the outside to the inside of the disc. Also known as Opposite Track Path (OTP) or DVD-9. This is the commonest formatting for long programming, as a DVD player's laser reads to the end of the first layer and then merely has to refocus on the second layer to continue with the disc. The RSDL point of a disc is usually at around the mid-point of the programming on the disc, and most players will exhibit a slight pause of the order of 1/2 second at this point as the laser refocuses.

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