czietz wrote:I have to see how this can be mapped to the scp file format. As far as I understand it always stores complete revolutions.
Yes, you are right. If you want to store it as SCP then you can't use fractional revolutions. You would need to decide if it's worth to store two revolutions, use other formats, or just ignore the issue of data under the index.
For ST disks it happens mostly (probably only) on copy protected disks, and even then, not on every copy protected disk, of course. If you want to consider other architectures, especially some using 5.25 disks, then it is much more common. E.g., Atari 8-bit drives didn't have an index hole detector at all. So all user made disks had data under the index.
There is a possible workaround that is making sure that the stored revolution can be used as a circular buffer. You would need to analyze two consecutive revolutions, perform some pattern matching, and then you might need to remove or to add a couple of transitions from the next revolution. This is because the index pulse has some jitter. But this is a bit of a kludge. Not every tool would know how to recover the data under the index from a single stored revolution.