Crop Video Thumbnails for Preview Thumbs
Step 1) Click the Content tab and select "Manage Content Sets"
Step 2) Click Thumbs next to the video set you wish toedit
Step 3) Click Select and crop a thumb from this set in the black bar
Step 4) In the Preferred Image Source
Step 5) Click the thumb displayed on the page
If a valid media type was selected from the dropdown, this will load a
Step 6) If you scroll down, under the video you will see options for navigating frames in the movie. You can skip ahead 1 frame, 10 frames, 100 or 1000 frames. Navigate to a frame you would like to crop.
Step 7) Click the Create a Thumb from This Frame button. This will load the image into the cropper.
From here the process is the same as when you crop a photo for use as a thumbnail.