Frame strip behaviour
Each thumbnail represents an actual display-order source frame at the selected interval. With the normal one-frame interval, the cells immediately before and after the selected centre cell are the preceding and following frames, not GOP-spaced samples.
The strip adapts its cell count to window width while maintaining the source display aspect ratio. At the beginning or end, black inactive cells occupy unavailable positions so the current frame remains centred.
Navigate from the strip
Click an active thumbnail to move to that frame. Number shortcuts select visible positions. The green outline identifies the selected cell; the thin status colour within each valid cell identifies whether that frame is kept or cut.
Background generation
Thumbnail decode is asynchronous. Blank valid cells can fill after the main preview becomes usable, especially on remote, very large or damaged sources. Navigation remains responsive while work continues.