Flip

Mirrors the video frame. Accepted values are h (horizontal, left↔right), v (vertical, top↔bottom), and hv or vh (both axes).

• flip=h — horizontal mirror (left↔right). Use this to un-mirror front-camera or selfie footage so on-screen text reads correctly.
• flip=v — vertical mirror (top↔bottom).
• flip=hv (or vh) — both axes simultaneously. Equivalent to a 180° point-flip; produces the same pixel result as rot=180.

flip is applied after rot — the frame is rotated first, then mirrored. hv and vh are identical (order-independent). Unrecognized values are silently dropped and the render proceeds un-flipped rather than erroring.

flip does not swap output width and height — it is a pure mirror operation.

flip takes effect only on visual render outputs. It applies across the same output types as rot: fm=mp4 / webm, fm=hls / dash, fm=gif and animated webp / apng, still images, and spritesheet frames. It is ignored for fm=vtt and audio-only outputs.