CD Burning: Pros, Cons, and Something about

Hacking Secrets. Brake Fluid for CDs

The arrival of high-speed CD-ROM drives has resulted in a large number of problems. The popular opinion is that the cons far outnumber the pros. The list of drawbacks includes terrible noise, vibration , and broken discs. Who needs it? Besides, many algorithms for binding to CD feel somewhat uncertain at high speeds. Hence, protected discs do not start on the first attempt, if they ever start at all What can we do about this? Naturally, we just slow them down! Fortunately, most drives support the SET CD SPEED (opcode 0BBh ) command. At first glance, there is no problem at all ”just specify the required parameters. However, things are not as simple as they seem.

The first nuisance (minor, but still annoying) is that the speed is specified in KB per second, rather than in x (note that the measurement unit is KB rather than bytes). At the same time, single speed corresponds to a throughput of 176 KB per second. What about double speed? If you deduce that it will be 352 (2 —176), you are mistaken. The speed is actually 353! Triple speed does equal what we would expect: 176 —3=528. However, 4x speed once again deviates from what would seem logical, being 706 rather than 704 (4 —176). An incorrectly specified speed will result in the setting of the speed one grade lower than expected, and the correspondence between the grades and stages will be ambiguous. Suppose that the drive supports the following range of speeds: 16x, 24x, 32x, and 40x. If the specified speed (in kilobytes per second) is lower than the nominal 32x speed, the drive will operate at the next lower supported speed, 16x in our case. Hence, to translate the x into kilobytes per second, they must be multiplied by 177 rather than by 176!

The second nuisance (much more significant and considerably more frustrating) is that the standard specification does not contain a command producing the complete list of supported speeds. This information must be obtained by means of trial and error. Before starting the trial, a properly operating program must make sure that there is no disc in the drive. If there is, it must forcibly eject it. As a matter of fact, running a low-quality disc at high speeds might result in the disc exploding, rendering the drive unusable. The user must be absolutely sure that the disc inserted into the drive will rotate at exactly the speed that is requested , and that the program won t increase the rotation speed without justification.

The third nuisance (of a horrifying nature this time) is that some drives (TEAC 522E, for instance) successfully swallow the SET CD SPEED command and confirm the changing of the rotation speed by returning its new value in MODE SENSE . However, the actual rotation speed remains as before until the disc is accessed once again. Therefore, it is wise to issue a command for reading a sector from the disc directly after the SET CD SPEED command (if the disc is present). Measuring the drive speed without a disc in the tray is pointless, suitable only for building the sequence of supported speeds, because all of the previous speed settings become invalid after inserting a new disc into the drive. Thus, the optimal rotation speed for each disc (from the drive s point of view) must be determined for each individual disc. The drive also has the right to change the rotation speed by decreasing it if the read operation is not going well, or increasing it if everything is OK.