MKVToolNix DOES NOT RECODE the video. No quality is lost – the file is demuxed (separated into its constituent parts – video – audio – subtitle files – and etc.) and then remuxed (recombined). Video and audio data is NOT altered.

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Download for Windows: https://www.fosshub.com/MKVToolNix.html

Download for other OS: https://mkvtoolnix.download/downloads.html

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To ADD/REMOVE Subtitles (example picture below)

1. Source Files

1. Drag-n-Drop the original video file.
2. ADD subtitles: Drag-n-Drop the subtitle file you want to add then ▼▼▼

2. Tracks, chapters and tags

1. DESELECT the track (un-check the box) to REMOVE subtitles and/or other tracks.
2. SELECT the tracks (check the box) for all files you want included in your output file.
3. HIGHLIGHT (select) the new SUBTITLE track then ▼▼▼

3. General Options (highlighted track)

Change the General options as needed (see picture) then ▼▼▼

4. Delay/Advance Timing (if needed – highlighted track)

Timestamps and default duration – DELAY (in ms)

NEGATIVE millisecond number (1000 ms = 1 sec) to make the subtitle appear earlier.

POSITIVE millisecond number to make the subtitle appear later.

5. ReMux (re-combine) the video file

Click the Start multiplexing button to create the new video file with the added/deleted subtitles and other tracks.

To be continued…