Crop your frame
Drop unwanted edges from any live source, in percent so it survives a resolution change.
Any layer's inspector has a crop control — four fields, each a percentage of the original picture rather than a pixel count.
Crop a layer
Open the layer's settings and set the four crop fields to trim its edges. Percent is deliberate: if your phone drops from 1080p to 720p mid-stream (a weak connection, for instance), a percent-based crop keeps framing the same part of the picture; a pixel-based one wouldn't.
How to verify it worked
The frame diagram shows the cropped rectangle immediately; press Apply and the live preview reflects it too. The top indicator moves to Re-composing if the scene was previously a byte-for-byte pass-through — cropping always requires an encode.
What's next
Build a vertical frame — a platform-specific layout, not just a crop of the wide one.