In a recent post on Moodle.org forums Mary Cooch (@moodlefairy) the Community Educator on Moodle.org posted about the new feature in Moodle lessons activity.
In the new feature which will be available from Moodle 2.9 onwards you can restrict the lesson activity on time basis which means teachers will be able to set “time spent” as a completion condition for a Lesson.
With this new feature, you will be able to specify that the student must spend a minimum time in the lesson – 80 minutes here for instance – before the activity is marked complete.
So, the students will not get the activity completion checkbox until they watch the video for more than the specified time. They receive a message that they completed it in less than the required time and therefore the completion box is not ticked.
For more details, read the tracker issue at: https://tracker.moodle.org/browse/MDL-48715