I'm running windows. And I have a mp4 video, and subtiles .srt. can I import/remove the subtitles into the video. Without rencoding if possible Does such a tool exist?
If you mean using "soft subtitles" (viewing video from two separate files but files not modified), I would use Media Player Classic - Home Cinema MPC-HC.
Both video and subtitle files need to be in the same directory, and have the same file names.
If you mean "hard subtitles" (permanent placement of subtitles in the video), I would use Avidemux.
Hard subtitles always require re-encoding. The resulting subbed video file can be played with any video player that supports the video codec.
With soft subtitles you can turn the subtitles off. The easiest way to turn them off is just to rename one of the files so the filenames aren't the same, or move one to another directory. Then the video won't pick them up