CTA Graphs

17 July 2001

The following are timing graphs for a Copylock track and a "long" track. Pretty cool.

It is now known that the time sampling works 100%, so the work on compression can start. The graphs look like exactly as expected, there is room for improvement on the look, but it does not matter from a functional perspective.

Update

We were not going to change the graphs, but we noticed that the density information is mirrored on a Copylock track. When this was being changes, we improved the output quality too.

Lets explain that.

The black line in the middle is the theoretical track optimum. It is of course impossible to reach this optimum with an analogue-based device, i.e. a floppy drive.

The X axis is the track data starting at left edge and ending on the right, and the Y axis is the density of data at any position (X) on the track.

The output is now changed to be an absolute +15/0/-15 percent of the optimum value, that is, the maximum displayable value. This looks much nicer than the “zoomed-in” image generated previously, and is also easier to read at a glance. The upper area (above optimum) is higher density, the lower area (below optimum) is lower density.

For example, this Copylock image shows about plus 6-7% density before the middle block, the middle block is slightly off normal speed, and after the middle block it is minus 6-7% density.

This long track contains about about 12% more data than a normal track would. Note that the first few bytes of this long track are not written - the sudden vertical line at the beginning.

The normal track’s data shows fuzziness, but this is normal, it is how the device works.

These tracks are the same as the previous ones, but much smoother, this is due to higher sampling rate only possible by imaging the disk with a faster CPU. As you can see, using a faster CPU to image the tracks gives cleaner results, but slower CPU‘s are still okay as long as they are above our minimum specification.

Now to really write the compressor...