JimDrew wrote:There is nothing "pushed" to any revolution. The dump is straight without any modifications done. The index to index pulse time is used to determine the exact position of where the bitcells are split on multi-revolution images. You have to use the index to index pulse time, along with the total bitcell times added together to get the exact spot of where the index pulse appears in the middle of a bitcell.
Here is a zoomed view of track 8.0 from Turrican. As we can see the No Flux Area overlap the Index. Not so obvious from the picture the NFA flux (flux 0 of the revolution) is 4.3 ms long and starts 1.3 ms before the index (and therefore terminates 3 ms after the index).
Here are the data from SCP
Code: Select all
Rev 0 – Flux count = 39289 – Index Time = 199940300
Fluxes = 1344900, 5275, … , 24625, 2700
Sum of fluxes = 198625575 – Delta = 1314725
Rev 1 – Flux count = 39290 – Index Time = 199922800
Fluxes = 4298950, 5300, … , 24625, 2700
Sum of fluxes = 199923400 – Delta = -600
Rev 2 – Flux count = 39290 – Index Time = 199922500
Fluxes = 4296950, 5275, … , 24625, 2675
Sum of fluxes = 199921925 – Delta = 575
Rev 3 – Flux count = 39290 – Index Time = 199911075
Fluxes = 4298700, 5300, … , 24625, 2675
Sum of fluxes = 199911100 – Delta = -25
Rev 4 – Flux count = 39290 – Index Time = 199923575
Fluxes = 4299225, 5300, … , 24625, 2700
Sum of fluxes = 199923550 – Delta = -25
I thought I could make sense of these data to find out the position of the first flux but now I am lost? For the first revolution the first flux is 1.345 ms and the sum of flux is 198625575. So the difference with the index time (199940300) is 1.315 ms
In reality the post index part of the first flux is 3 ms and the position of the index is 1.3 ms. Where can I find these numbers?
Also strange is the fact that the first revolution has 39289 transitions where all the following have 39290. Seems not so important but the strange thing is that if you look at the values they start and ends with similar values. Not possible to easily compare all transitions but it seems like one transition is added somewhere in the middle? For information KF results have two transitions less (39288) and starts and ends with similar values?
In most cases the position of the index inside the first “normal flux” is not important (only pushing the position by few µs), but in case of NFA it is bad not to be able to describe the reality.
So questions are:
- during sampling the counter is reset each time a new transition is detected. Correct?
- For the first revolution the counter is started when the index is found and reset at the next transition after the index. Therefore, the value is supposed to be the post index part of the first flux. Correct?
- Assuming above is true why we do not get the right number for Turrican?
- How can I find the position of the index?
If you want to test the image you will find it here https://mega.nz/#F!9RJixYhI!ozJAY06nUpYj2vzpuWORRg