Custom Motion Vector AOV with Motion Vector shader?

[excentriPMNA2]

Custom Motion Vector AOV with Motion Vector shader?

I followed the instructions of manual---

https://support.solidangle.com/display/A5AFMUG/Custom+Motion+Vector+AOV+with+Motion+Vector+shader.

but, I can't make custom motion vector AOV.

I made the following steps.

1. make a custom AOV
2. The name of the custom AOV changed into "mblur"
3. The Ai Motion Vector shader assign to the custom AOV.
4. I enabled Encode Raw Vector in the Ai motion vector shader, and I set Start Time : 0 End Time : 1.
5. In Render Settings, i enabled motion blur, and Position : Center On Frame , and Length : 1.
6. in order to disable motion blur, i checked Ignore Motion Blur checkbox in Diagnostics tab.

what is my mistake?

I have another question.
What is the role of Start Time attribute and End Time attribute in Ai Motion Vector shader?

in Render Settings windows, When Position set to Custom, what is difference between the Start attribute and End attribute in Render Settings, and Start Time attribute and End Time attribute in Ai Motion Vector shader?