It is not usually a good idea to leave any titles and captions untranslated.
This spoils the impression that this is, for example, a Chinese video for a Chinese audience.
If you are making a new video, the scriptwriter and editor can avoid using too much text on screen, or can at least design it to be changed easily.
If the new language does not use Roman (Western European) script, the editor may have problems creating new captions, as the fonts may not be available in the edit suite.
In that case, get the translators to print out the captions in large text, one to a sheet of A4 paper, so they can be scanned in.
Remember to ask them to label them, so you know which is which and which way up they go!
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