Good day! I'm looking for MKVToolNix equivalent software for .MP4's. I will use it in a video file without subtitles, I'll find it's subtitle and merge it with the video file just like what I did in MKVToolNix. Thanks!
Muxing a file simply means to extract individual streams out of existing container files or mix existing streams together into a new container file. For MP4, this can be done with ffmpeg and the
-c copy switch. If you don't want to write command line inputs, XMedia Recode is a good, free GUI for ffmpeg. There's a documentation on the website, simply select Direct Stream Copy to avoid reencoding the individual streams.