MFDigital CD DVD Information Library
Wednesday, June 23, 2004
TechNOTE - Buffer Under-run Protection & Its Value in Duplication
What is it?
It is known by many names, "BURN-Proof", "SafeBurn", and "lossless linking" to name but a few. Regardless of the name, they are all buffer under-run prevention strategies. In the dark days of CD-R recording, before we had BURN-Proof and the like, if a drive's on-board buffer became empty, the write would fail leaving an incomplete and unusable disc. The on-board buffer of the drive is analogous to the fuel tank on a military aircraft, which relies on periodic in-flight refuelings. If the jet's fuel runs out, the plane will crash. The host computer, or duplication controller, is the refueling aircraft. If it cannot supply DATA as fast as the drive consumes it, the write process will fail. Essentially, what buffer under-run prevention gives you is a means to pause while the host catches up.
Why do I need it for my PC?
Buffer under-run prevention was really a response from drive manufacturers to overcome limiting factors that were preventing drives from going to higher write speeds. Many PCs were, and still are, simply not up to the task of writing at these higher speeds. The burden of handling so many technical support calls was more than anyone was willing to deal with. The answer was simply to design the drives in a way whereby if the computer could not deliver the data as fast as the CD-R drive required, it would simply pause and wait for the PC to catch up. No coasters, no tech calls.
Why does it not make sense on a high performance duplication system?
A better analogy for CD-R writing when using buffer under-run prevention is that of a car. If a car runs out of fuel, you can simply fill up a gas can, add fuel, and continue on your way. No plane crashes here. Using the car analogy, what would be the down side if your tank was very small and you were embarking on a long drive whereby the distance between gas stations was greater than the fuel capacity allowed? Well, you would run out of gas frequently and find yourself walking along the road to fill your gas can only to walk back to your car, refill, and continue on your way, repeating this step as often as necessary. So in effect, if the host PC or duplication controller cannot provide data as fast as the CD-R drive writes, the drive will pause, wait for the buffer to refill, and then begin the write process again. The downside here is performance. This can take from one to several seconds per actuation of buffer under-run prevention. A one-drive 32x copier from one company might easily out-perform a 52x unit relying on buffer under-run prevention.
The MF Digital difference
MF Digital designs its duplication and publishing systems so that buffer under-run prevention strategies are not needed. This is achieved through MF Digital's own precision duplication controllers and software, and the use of high-speed hard drives, fast processors, and plenty of memory. When using MF Digital's PC based systems such as the Scribe, be sure to adhere to the minimum system requirements.
If you have any questions that might make an interesting TechNOTE or white paper, please do not hesitate to send them in. Please forward your questions or suggestions to John McGrath c/o MF Digital. 121 Carolyn Blvd., Farmingdale, NY. 11735, or email firstname.lastname@example.org, or http://www.mfdigital.com/