Hello, I would like to know if it is possible to edit an mp4 video on After Effect by changing only 3D letters without changing the rest of the video content. They are Chinese script and I would like to change only Chinese letters to European letters. The original video format is mp4.
Of course you can.
Depending on the shot and your art concept, you might have to remove the chines letters from the scene using image retouching and tracking techniques. As soon as the shot is clean enough, you can add any letter you want.
If you show us an example frame, or a short clip from the video, we can give you a more detailed help.
That link is showing "video is unavailable"
Your video shows as unavaliable, so we can't refer to your exact scene but what you need to know - mp4 format is not like PSD format or f.eg. a car where you can go and change wheels or lights but the rest will stay the same. mp4 format is more like a picture of your car - if you wish to change anything you have to retouch your image.
I'm not sure that clunky parallel is clear enough but long story short:
1. No you cannot simply open mp4 file in AE push edit and edit your text or change language or font
2. What you can do is - depending on your scene - use some technics available in AE to mask, retouch, "remove" your text and use text tools to put a new one in the same place. What tools to use to remove and then put a new one - here we need to see your file because it can be just a simple case of masking blurring and matte or it can be something that will need 2d/3d tracking, content aware fill etc.
If there is anything that you want to replace in a video you have two choices. Figure out how to fill the area, your 3D text Chinese Characters, with something that will look like the original video before the characters were added, or add something that is big enough to cover up the thing you want to hide.
There is no magic button you can push. There is no plug-in. There are tools that may work fairly automatically with some kinds of shots, but there are also shots that would require you to synthetically recreate the original video by 100% manual means. Show us a frame or show us the video and we might be able to make some suggestions.