After extensive testing, we have found that a blend of key-presses, mouse movements and data recording actions can give us an accurate measure of how much time is being spent on video work.
In the event of a situation where there is dissagreement about the calculation of work time, we can analyse the task meta-data, and make a judgement as to whether there is a problem with our algorithm, and adjust it if necessary.
As a Video Datapad data provider you are made aware of this calculation when your enumeration provider submits the data for a video task, and can override it manually if you disagree with the calculated cost.