Function addVideo

addVideo(
    extra: PhiraExtra,
    path: string,
    startBeat: number,
    options?: CreateVideoOptions,
): number
Add a video background to the extra.
Parameters
- extra: PhiraExtra
  PhiraExtra to modify.
- path: string
  Path to the video file (e.g., "bga.mp4").
- startBeat: number
  Beat at which the video starts playing.
- options: CreateVideoOptions = {}
  Video options.
Returns number
The index of the newly added video.
Example
```
const extra = createExtra(120);
addVideo(extra, 'background.mp4', 0, {
  scale: 'cropCenter',
  alpha: 0.8,
  dim: animateValue(0, 4, 0.5, 0),
});
```
- Defined in extra.ts:997