Why is my .mkv video so big?

[Vorpike]

I had a lot of problems with this 7Gb .mkv file, like formatting my USB to NTFS. But I'm done with my theories on how to solve this and to turn to you guys. Why is my 2 hour long video so damn large? I'm thinking it's because its loaded with 4 sets of subtitle, each with their own fonts, but when I tried splitting it with toolnix, I got 4 files that were around 2Gb each, but were, for some reason, 3 hours long. I couldn't scrub through the video to verify that its correct, because this huge file is really laggy, and I can only watch it from start to finish without searching through it (not an option). So my questions are, why is this short video so large in size (the resolution is only 700), and how do I make it so I can actually scrub through the video?

[Exilant]

Hi,

you do want to get rid of some features (unused subtitles) and decrease the filesize, am I right? I suggest to reencode the file, strip it of all the unused subtitles and increase compression rate. The size depends on the various streams hidden in your mkv-file and their compression. When your videostream is nearly uncompressed data, it might blow up the size to 7GB.

Exilant