DEAF - adding subtitle 'srt' files for hard of hearing to MP4

Hi everyone

Does anyone know if you can combine an MP4 video file with an SRT file? SRT files contain the on screen subtitles which deaf or hard of hearing people use so that they can understand what is being said. SRT files are often kept separately to the MP4 file but in the same folder, but some programs like iTunes just ignores the separate SRT file and won't display the on screen subtitles unless the SRT file has been packaged inside the MP4 file somehow.

'Handbrake' can do this, but it has to completely re-transcode each file and it takes ages. Is MP3TAG able to do this quicker and more easily??

Can anyone help with this? Thanks very much!

The only fields that I know that holds some kind of lyrics or subtitles are UNSYNCEDLYRICS and SUBTITLE.
See https://docs.mp3tag.de/mapping for a list of supported fields.

If adding those subtitles (like closed captions) to a file means that the actual video or audio contents has to be modified, then MP3tag is not the right tool as MP3tag only modifies the tags at the front or at the end of files but not the stream inbetween.