50fps mp4 where every frame is duplicated

[pooksahib]

Hi. I have an mp4 file which, to my eyes, plays OK but I've just realised that there are 2 identical frames for each image throughout. Presumably, it would be better to reduce the file to 25fps by removing the duplicate frames. Is TDecimate() my best option here? And, if so, is the command simply this:
last.TDecimate()

Thank you.

[sneaker]

You need to set the cycle.

TDecimate(cycle=2)
https://avisynth.org.ru/docs/english/externalfilters/tivtc_tdecimate.htm

If the pattern is constant something simple like SelectEven() should also do the trick.

Note: if the frames are exact duplicates they usually compress to almost zero anyways. So if your goal is just to reduce the file size I would not do this because you will lose quality, waste time and achieve nothing.

[pooksahib]

Thanks, sneaker. File size isn't an issue, just the possiblity of getting a better video. I said at the beginning that it plays OK as far as I can see - that must be your 'compress to almost zero' kicking in. I'll probably just leave it, then.

[jagabo]

Decompressing the source and compressing it again (with a lossy codec) can only make the picture quality worse.

[hello_hello]

I wouldn't bother unless you need to re-encode for some other reason. If you're using a 50Hz TV you'll get one screen refresh per frame at 50fps, or two screen refreshes per frame at 25fps, so it should look exactly the same if every frame is repeated for 50fps.

[pooksahib]

I did a re-encode simply because the original vid was so large. SelectEven() did a fine job so thanks to you all for the advice.