How to create a mask by specifying a frame

[Kazuki21878849wyhn]

I'm looking for a way to create a frame-based mask from a script (jsx).

I can create a mask based on time (seconds) with addKey (), but I don't know how to mask based on the frame.

keyIndex1 = newMask.property(1).addKey(frame * frameDuration);
newMask.property(1).setInterpolationTypeAtKey(keyIndex1, KeyframeInterpolationType.HOLD);

If anyone knows how to create a mask based on a frame without using addkey (), please let me know.

[Mylenium]

Time conversion methods such as frameToTime() are available both in scripts and expressions. That's all you need.

Mylenium

[Kazuki21878849wyhn]

The frameToTime () function was not recognized as a function in the script.
By the way, is there any other way to convert to frame unit?

[Mathias Moehl]

Not sur ewhat your question is. You already have the answer how to convert number of frames to a time in seconds in your example:

frame * frameDuration

[Kazuki21878849wyhn]

In the official addKey () function description, the addKey argument specifies the number of seconds.
Basically, there is no problem with specifying the number of seconds.
But,In the case of a long movie (after about 8 minutes), problems such as the mask collapsing, the rotobeje not being applied, and an unrelated mask appearing will occur.

https://community.adobe.com/t5/after-effects-discussions/unable-to-create-rotobezier-mask-on-long-vi... 

While investigating the cause of the problem, I suspect that the cause is that the number of digits in the value of frame * frameDuration becomes large.
On the other hand, if you reduce the number of digits in frame * frameDuration, the frame will deviate from the frame you want to mask, so you cannot reduce the number of digits poorly.
Therefore, this time I was looking for a method that can be set on a frame-by-frame basis.