How can I remove subtitle streams from an m4v/mpeg4 video?

[extent]

How can I remove subtitles from an m4v (mpeg4) video file? There are 3 seperate subtitle options that are selectable within the video (I can see the 3 subtitle options in VLC player), so are not embedded as part of the video-but are part of the m4v file-if that makes sense!

In VLC Player, stream 1 is my mpeg4 video, and stream 2 is aac mp4a audio.
Streams 3,4 and 5 are "subt" files - is there a program I can use to extract and remove these streams from the video? I know I can watch the video with subtitles disabled, but I am trying to find out the easiest way to remove these 3 streams without affecting quality?

thanks for any help

[Baldrick]

Remux with mymp4boxgui or yamb or mp4muxer. Open the m4v/mp4, remove the subtitles, save as new mp4.

[extent]

I tried the yamb gui for mp4box, and that removed the subtitle streams with no issue from the original I initially tried to extract the subtitles first so I could analyse them before removal (as I was having a problem with one of them) but yamb gave me an error (could not find mp4box) even when I had given the location. thanks