Hello!! I am finally here with some answers...
Thank you for sending all the examples @Plenum Here's what @pietro said about the importance/inevitability of grainy movies:
The lack of consistent quality in the movies with respect to blurriness, graininess, overexposure, etc. can be frustrating, and over time, we are improving our methods to get higher quality data. But having a variety of calibration videos that includes sub-optimal image quality is needed to help train people so they can provide more accurate answers when confronted with real vessel images that have similar characteristics. We are doing our best to "meet in the middle" - that is, improve image quality, and train users to annotate when image quality is sub-optimal.
Basically, in some cases we simply have to deal with the data as it comes from the lab, and sometimes the imaging and/or preprocessing conditions lead to worse quality movies. But as long as we can tell flowing from stalled in them, we're good to go, and its invaluable for our purpose!!
Thank you for bearing with us! Real is not always beautiful, haha!