Frame geometry: rotate, crop and scale video
The "Geometry and framing" page is in the FRAME section. The settings on this page move the picture itself. Each of them changes the position of almost every pixel at once. For platform algorithms this is a strong change, and for the viewer it is often unnoticeable. The ranges work the same way as everywhere else: see how uniquification works.
Seven geometry settings
| Label | What it does | Range and units | Default |
|---|---|---|---|
| "Scale video" | Changes the scale of the picture inside the frame. The file resolution stays the same | percent, from -100% to +100% | on, from -10 to 10 |
| "Rotate video" | Rotates the frame by a random angle | degrees, from -50° to +50° | off, from -2 to 2 |
| "Crop edges" | Cuts pixels off each of the four sides and stretches the frame back | pixels per side, from 1 px to 30 px | off, from 1 to 5 |
| "Lens distortion" | Bends the frame outward or inward, like lens distortion | percent, from -50% to +50% | off, from -15 to 15 |
| "Perspective" | Shifts the four corners of the frame and stretches the picture back into a rectangle | percent, from 1% to 50% | off, from 1 to 10 |
| "Stabilization" | Compensates for camera shake by moving the picture frame by frame | percent, from 1% to 100% | off, from 25 to 75 |
| "Camera zoom" | A slow zoom over the whole video; the frame center stays still | percent, from 1% to 50% | off, from 5 to 15 |
In a new project only scaling is on. The other six settings are off.
What depends on what
There is no nesting on this page at all.
- All seven settings are equal and always shown.
- None of them opens or hides a neighbor.
- Two more settings sit on the same page. "Mirror the video horizontally" is a list with the options "No", "Always" and "Randomly". "Frame border" is described on the texture and detail page.
Stabilization slows video creation the most
This is the most expensive setting on the page and in all of frame uniquification. It adds more work than file compression at a medium level. On a long video the difference in time is visible right away.
It only makes sense to turn it on for a shaky handheld video. The side effect is exactly what uniquification needs: almost every frame is shifted relative to the original. On a static tripod shot the edges may float slightly.
The slider has only four real steps. The values 30% and 35% give the same result.
Cost in time of the other settings
Every setting on the page recalculates pixel positions, that is, it redraws the whole frame.
| How much it slows things down | Settings |
|---|---|
| Very strongly | "Stabilization" |
| Noticeably | "Rotate video" |
| Moderately | "Perspective", "Scale video" |
| Slightly | "Lens distortion", "Camera zoom" |
| Almost not at all | "Crop edges". Every pixel is still recalculated |
What you see at the ends of the range
| Setting | What you see at the end |
|---|---|
| "Scale video" | When scaled down, a blurred copy of the same frame is visible around the frame. When scaled up, the frame edges go outside the border |
| "Rotate video" | ±50°: to remove the black corners, the frame is enlarged about twofold. Half of the picture stays outside the border and sharpness drops noticeably |
| "Crop edges" | 30 px: the shift is still barely visible. The crop is limited to a tenth of the frame on each axis |
| "Lens distortion" | ±50%: the distortion is barely visible. This is one of the least noticeable settings in the area |
| "Perspective" | 50%: the frame corners wander by 5% of the frame size, and the picture looks visibly skewed |
| "Stabilization" | At any step the picture is shifted frame by frame. On a tripod video the edges may float slightly |
| "Camera zoom" | 50%: by the end of the video the frame is enlarged one and a half times, and the movement reads as an effect |
"Scale video" has a separate subtlety at the lower end. The slider goes down to -100%, but at the very end the frame stays at its original size. There is no scaling down to zero: zero width means "leave as is". Checked by measurement.
FAQ
Why does rotating by a large angle blur the picture?
Before rotating, the frame is enlarged, otherwise black triangles would remain in the corners. The larger the angle, the stronger the enlargement. At ±50° the frame is enlarged about twofold, and half of the original pixels are stretched over the whole frame. A sensible range is from 1° to 3°.
Does "Crop edges" change the size of the finished file?
No. After the crop, the frame is stretched back to its original size. The file resolution stays the same. The shift is barely visible, yet every pixel is recalculated.
The results table shows a dash for "Crop edges". Why?
The crop is limited to a tenth of the frame on each axis. If after this limit all four sides come out as zero, the setting is not applied at all. Such a copy gets a dash in the results table.
Why do 30% and 35% stabilization give the same result?
Stabilization has only four steps of search area. Neighboring percentages land on the same step. This does not cancel the spread of the range: different copies still get different steps if the range is wide.
Which geometry settings work well together?
Scaling, edge crop and camera zoom combine easily. Rotation and perspective together are already noticeable to the viewer. Keep stabilization separate because of the time it takes. For more on how noticeable changes are, see result quality.