Easiest to see the problem with short animation sequences. So import an animation with time range 0 to 3 ( 0.1 seconds long if animating at 30fps).
UE4 will correctly display the animation length of 0.1 seconds.
UE4 will correctly say the animation has 4 frames. This is slightly counter-intuitive but basically you count frame 0 where no time has passed.
However if you open the anim in persona and look at the current frame a frame is added to the timeline which shouldn’t be there. For example in maya you may have a time range 0 to 3, if you import this you will see the time range now goes from 0 to 4. If you use the play back buttons to frame advance you will see that frame 1 is 25% of the way through the animation with a current time of 0.025. Frame 1 should match whichever package you animate in and should be 33% of the way through the animation at a time of 0.333. At 30fps every frame should be 0.333 apart.
I assume this is a simple mistake due to the slightly counter-intuitive nature of number of frames. It only seems to effect the frame displayed in persona all other timings seem to work. However it is slightly awkward when it comes to adding FX/sounds/notifies etc on specific frames. The error is pretty small, and gets smaller and smaller the more frames are exported, but for people like me who prize precision it is annoying.
It is known that this way of displaying the frame ranges can be confusing(See here). We are considering modifying this, but as of right now this is not high priority. Thank you for your concern.
Sorry, I thought I had replied, looks like I didn’t send properly.
Anyway, not sure you can describe this is as a deliberate choice on how to display frames. I don’t really understand the response in your link so maybe I am missing something, but a frame is not a time range, it is a one dimensional point in time. For example there is no problem in importing a single frame (well UE4 doesn’t support that, but that’s a different bug).
To reiterate if animating at 30fps, frame 0 is the first frame at time 0 seconds, frame 1 is at 1/30 seconds, frame 2 is at 2/30 seconds and so on. This is not the case in UE4, depending on the number of frames in the anim. The number of imported frames should not effect the distance between frames in the timeline. I don’t think there is a way to reinterpret this?
I understand that this will never be a priority and likely never resolved, it’s just a shame as depending on how the code is written you would only need to edit one line of code.