WAN2.1 FLF2V: Incorrect MASK Creation???

[KyujinHan]

Please check detail in issue.

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The issue code: FLF2V generate function

For I2V, masking shape like as below:

[[1, 0, 0, ... , 0]
[1, 0, 0, ... , 0]
[1, 0, 0, ... , 0]
[1, 0, 0, ... , 0]]

I understood: when the mask is 1, input video frame does not change.
(*Mask shape: [1, 4, 21, 60, 104] = [B, C, F, H, W])

But in the FLF2V case, masking shape like as below:

[[1, 0, 0, ... , 0]
[1, 0, 0, ... , 0]
[1, 0, 0, ... , 0]
**[1, 0, 0, ... , 1]]**

Here, why the last frame mask has 1 only in last channel??
Is there anyone who can explain this part?

[KyujinHan]

@Steven-SWZhang