Finding equivalent x,y position values in HD video

nyarlothothep

Hi, I have a video that I changed from 720x540 to 1920x1080. I want the animation of the energy beams in this video to have the same positions as they move across the screen relative to the 720x540 version. For each animation of the beams I have two position key frames. I need to work out what the values for these key frames are for the 1920x1080 version but don't have the maths skills to find them. Here are the values for the topmost beam in 720x540.

start position

x: 1241.8 y: 278

end position

x: 400.1 y: 195

Is there a way to translate these values to their relative equivalents in HD?

Yakuza

I might be missing something, but how can something that is in a 720 * 580 screen size have an x co-ordinate of 1241.8?.

In general terms, if you've upscaled 720 * 540 to 1920 * 1080, then all you need to do is multiply your x (width) coordinate by 8/3 (1920/720, reduced to its lowest terms) and double your y (height) co-ordinate by 2 (1080 / 540, reduced to its lowest terms).

So, for example a pixel at position 360, 270 (the middle of the screen) on a 720 * 540 screen would be at 960 (360 * 8/3), 540 (270*2) on a 1920 * 1080 screen.

I hope that helps.

nyarlothothep

Yes, this seems to be working. I forgot to mention that the energy beams start and end outside the frame as they travel into and out of view.

red_fox

I assume that the change in aspect ratio is intended? Also, that the video is streched to fill the higher resolution rather than scaled to be a best fit? (which would be 1440x1080 and have black borders 240 wide on either side)

nyarlothothep

It's being generated inside AE and the background image was originally in HD so I don't think there will be any problems with pixellation.

red_fox

I wasn't thinking of pixellation, just that if it presevered the aspect ratio then Yakuza's method won't quite work, however if the image is streched (linearly) then it will work.