Feature request: Auto-calculate Change Rate percent from target FPS

[fyhtma]

Is your feature request related to a problem? Please describe.

My workflow: I first create slow-motion clips in Topaz Video AI. For example, I take an 18 fps video and render it as 8x slow motion, so all extra frames already exist.

In WebM for Lazys I only need to change playback FPS back to a normal rate (for example 59.94 fps) and encode to H.265. The Change Rate dialog only accepts a percentage, so I must manually calculate values like (59.94 / 18) * 100 = 333% for every clip, which is tedious and error-prone. The Advanced → Target FPS option is not usable here because it enables minterpolate and is extremely slow.

Describe the solution you'd like

Add a Target FPS input directly to the Change Rate dialog.
When the user enters a value in Target FPS, the program should read the original FPS and auto fill the existing Set to % field using:

percent = (target_fps / original_fps) * 100

Example: dialog shows Original FPS: 18; user types Target FPS: 59.94; the app sets Set to %: 333. This should only act as a calculator for the current fast Change Rate function and must not enable minterpolate or other interpolation.

Describe alternatives you've considered

1. Manual calculation with an external calculator for each clip.
2. Using Advanced → Target FPS, which adds minterpolate and is far too slow for this use case.
3. Doing FPS changes with plain ffmpeg outside WebM for Lazys, which loses the benefit of the GUI.

Additional context

• WebM for Lazys version: v3.43.4
• Workflow: Topaz Video AI creates 8x slow motion from 18 fps; WebM for Lazys should only change playback FPS to about 59.94 and encode to HEVC (hevc_nvenc).
• Core issue: Advanced Target FPS is slow because of minterpolate, while Change Rate is fast but accepts only percent; I am requesting a simple Target FPS calculator inside the fast Change Rate dialog.

[argorar]

The result in your example is a whole number, in the cases where it have decimals it will be round and not exact. Check latest update.