Magic Mask tracking fail immediately on supersampled clip

If you try to use the Magic Mask on a clip where you selected 2x supersampling (well probably other values too, I didn't try), the magic mask tracking fails immediately.

I draw a stroke, it identifies the subject just fine for that frame.

The log shows :

Code: Select all

[0x7f9f5084b680] | SyManager            | INFO  | 2021-02-28 20:58:49,115 | [MagicMaskTracker]: Start tracking: Clip size: [640 x 360], Frame range: [47955, 54330], Frame offsets to track: [47955, 54330], VersionToFrameOffset: 0, Fast tracking: 1
[0x7f9f5084b680] | SyManager            | INFO  | 2021-02-28 20:58:51,541 | [MagicMaskTracker]: No more path to track. Stop tracking
[0x7f9da8442700] | SyManager            | INFO  | 2021-02-28 20:58:51,561 | [MagicMaskTracker]: Tracking has been aborted

Few notes :
* The timeline is 1280x720
* The 640x360 is the original clip size. After 2x supersampling, it should be 1280x720 and match the timeline.
* The 'input scaling' for the project/timeline/clip was set to "crop"

If instead of supersampling, I just set the clip to "fit" during input scaling, it tracks just fine.

Still buggy in 17.1 ...