Shotcut contains various video scopes to help with color adjustment and picture validation.
The video scopes represent the picture from the preview player. The preview player always displays as YUV 4:2:0. As a result, the representation in the scope does not necessarily represent the original source material. Nor does it necessarily represent what will be in the final export file.
Shotcut manipulates images by applying various services (filters, transitions, playlist, timeline). Different services operate on different image formats. Shotcut will automatically convert the image format as needed as the image passes through the processing pipeline from one service to the next. Depending on the services that user has applied an image may go through multiple conversions before it reaches the preview player.
Internally, Shotcut supports two image formats:
Note that a full range YUV image will be converted to limited range upon decoding. If a limited range source image has values that are outside of the limited range, those out-of-bounds values will be passed to the preview window (and therefore the scopes) unless they go through a conversion. In order to satisfy the needs of various services (transition, filter, etc) an image may be automiatically converted between YUV and RGB. These automatic internal conversions will result in out-of-bounds values being rounded down to be within the limited range.