How to make exact copy of a mkv/mp4... add subtitles

[jagman911]

When I try to use Wondershare Video Converter Ult or programs like it, to make a copy of a video file, to add subtitles, etc.... the resulting copy is huge, almost always twice as large.
These programs don't seem to be able to make an "exact" duplicate but only to customize. Is there any programs that has std settings to just make a copy, make smaller ...
All I need to do is maybe edit, add subtitles, lighten, darken... the same size, or reduce to save space.. Anyone?

Thanks

[manono]

What's wrong with just playing the subtitles along with the movie? It'll save reencoding and degrading the video quality.

Anyone?

Filesize is determined by bitrate. If you want a smaller size, give it a lower bitrate than it has.

[abolibibelot]

Filesize is determined by bitrate. If you want a smaller size, give it a lower bitrate than it has.

Or a higher CRF value, for a 1-pass encode, which is generally preferable. I don't know that Wondershare software, but it most likely has quality settings, which affect the CRF (Constant Rate Factor), even if it's named differently.

By the way, I've already seen MP4 files with "soft" subtitles, i.e. a SRT file muxed with the AVC video and AAC audio, yet it doesn't seem to be standard, and most tools don't allow it. Are there free and trustworthy tools which do allow to integrate subtitles in a MP4 container ?
Otherwise, MKV allows by design to integrate pretty much anything.

All I need to do is maybe edit, add subtitles, lighten, darken... the same size, or reduce to save space.. Anyone?

You may be able to add "soft" subtitles (see above) with no need to re-encode, but as soon as you apply effects like lightening / darkening, re-encoding is mandatory.
But you can also adjust the brightness level in the software player, or the TV / computer screen... that way you save time and avoid an otherwise inevitable loss of quality (especially if you transcode a low bitrate file with the same low bitrate).