I am trying to find out an easy (and preferably free) way to both embed subtitles without fully converting an mp4 file, and also how to extract a subtitle file from a movie file? Can anyone help?
There's no way to embed the subtitle without transcoding the final video. You can use VLC Player for embedding a subtitle- https://www.dedoimedo.com/computers/vlc-subtitles.html I don't think there's a way to remove an embedded subtitle since it is encoded into a frame just like the video. You could add a new subtitle over top of an existing one. You could cover up a subtitle using video editing software.
I've just used VLC, the end result had no subtitles for some reason. Maybe as I was using the portable version?
Did you add a .srt file where it asks for it. He doesn't mention adding it in the appropriate screen and I completely missed it. Ended up needless encoding. Once i did that, it worked great when I played it back from within VLC. Only two issues- 1. It added the name of the original file to the subtitle that I added I really didn't want it there. 2. It didn't output the converted file to where I designated. That part of the procedure is screwy. I'll have to work on it. By the way, I'm just using a copy that I downloaded several years ago. However, if you have all the options he shows, then it should work.
I found a better way. I used Subtitle Edit to convert the .ttml file to an .srt file. Then I used MKVMerge in MKVToolNix suite of tools to add the SRT file to the .mp4 file. The output is an .mkv file but I simply renamed the file extension from .mkv back to .mp4 and it works perfectly in my media player. The entire process is about 5 minutes too and no re- or transcoding at all to do. I think for some of you this is a brand new way as there is no transcoding, it simply embeds the .srt file into the .mp4 file, job done. Thanks for the help though guys https://mkvtoolnix.download/downloads.html