How do I convert 21:9 to 16:9 aspect ratio with AviSynth?

[VideoFanatic]

The phone's native aspect ratio is 21:9. How could I re-encode a 1080p video to 16:9 with Avisynth?

Somebody said that the Sony Xperia 5 IV phone when set to record video in 16:9 just crops 4:3 to 16:9. Is there any problem with doing that compared to if the phone could record natively in 16:9 and why would it do that crop instead of just recording in 16:9?

I'm not sure if I should record in 16:9 or record in 21:9 then re-encode to 16:9 with AviSynth?

If I convert 21:9 to 16:9 then am I just losing the sides?

[Sharc]

Not sure what you actually mean.
If the display of your phone is 21:9 (2.33...), a video recorded as 16:9 with 1080 height will have left and right black bars of 300 pixels width on each side.
If your phone records in 21:9 (2520x1080) and you want to play it on a 16:9 screen without cropping the sides you would have to resize and add black bars on top and bottom, like

spline36resize(1920,824)
AddBorders(0,128,0,128)

[hello_hello]

Somebody said that the Sony Xperia 5 IV phone when set to record video in 16:9 just crops 4:3 to 16:9. Is there any problem with doing that compared to if the phone could record natively in 16:9 and why would it do that crop instead of just recording in 16:9?

The phone possibly only records using a single aspect ratio so it crops to give you 16:9. I'm not sure there's any problem doing it that way. It's similar to matting for film.
https://en.wikipedia.org/wiki/Open_matte

If I convert 21:9 to 16:9 then am I just losing the sides?

Yes.

You could do it automatically using the Avisynth CropResize function in my signature.

To crop any video to 16:9 dimensions all you need to do is specify 16:9 output dimensions. Any 16:9 dimensions or any other output aspect ratio is okay. CropResize will also resize after any cropping if necessary.

CropResize(1920,1080) or CropResize(1280,720) etc for 16:9.

If you don't want to crop but want 16:9 dimensions with black borders instead, simply enable borders and CropResize and will add borders instead of cropping.

Original


[Attachment 71133 - Click to enlarge]

CropResize(1280,720)


[Attachment 71134 - Click to enlarge]

CropResize(1280,720, Borders=true)


[Attachment 71135 - Click to enlarge]