If the file is corrupted, tools like VLC's repair feature or specialized software can often fix corrupted MP4 headers [4].
Based on my search results, there is no widely known or specific software feature, article, or technical document directly covering a file named "RCT-721.mp4".
(e.g., Is it security footage, a project file, or a corrupted file?)
Use Handbrake or VLC Media Player to convert the file if it is not playing in certain applications [1, 2].
(e.g., Edit it, convert it, play it, or repair it?)
Use LosslessCut to trim, cut, or merge segments of the MP4 without re-encoding, preserving quality [3].
It is highly likely that "RCT-721.mp4" is a , such as:

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