frame in the clip. The routine that is supplied by the user has a single parameter (time) which is the "normalised time" for that clip. The first frame in the clip has time 0.0 and the last frame in the clip has time 1.0 (actually it is 1.0 minus the normalised timelength of a frame, it never fully reaches 1.0).
Developing a WebVfx overlay HTML filter using Shotcut alone is not easy, as most errors result in a blank screen, with no indication of what caused the error, or even what the actual error is. This is where the Shotcut WebVfx Framework that I
have developed comes in useful. It enables the development to be done using a modern browser, such as Chrome, or Edge, that has a comprehensive set of development tools (accessible using function key F12). See the following webpages for more details:
https://developer.chrome.com/devtools & https://docs.microsoft.com/en-us/microsoft-edge/devtools-guide