Part1 some knowledge about MKV video

What’s MKV video format?
An MKV file is a Matroska file, the Matroska Multimedia Container is an open standard free Container format. It is similar in conception to other containers like AVI, MP4 or ASF, but is entirely open in specification, with implementations consisting mostly of open source software. Matroska file types are .MKV for video (with subtitles and audio), .MKA for audio-only files and .MKS for subtitles only.

How to play MKV files on Windows?
In principal you can play MKV files on almost every Mediaplayer on Windows if you have the latest CCCP playback pack from Matroska Download Page installed, as most of these players are based on Microsoft DirectShow (TM).

Part 2 MKV Splitter - split MKV file, convert MKV file, add subtitle

1. Convert MKV file
Format supported
HD video ( AVI, MOV, WMV, MP4 TS, MTS, M2TS, MKV)
Common video ( AVI, WMV, MP4, MPEG, VOB, FLV, 3GP, ASF, MOD, MOV, etc.)              

Step 1 Click "ADD" to load MKV file.
Step 2 go to "convert to" to set the output format.
Step 3 go to "target path" to set the output location.
Step 4 hit "start" to begin the conversion.

2. Split MKV file
MKV file is a high definition file which takes up much space on hard drive. With this MKV splitter, you can trim particular part off the MKV file to save space.

Got to "Edit – trim"
Click the Trim button to open the Trim window and trim the current video file by dragging the Start Time slider to set the start time and dragging the End Time slider to set the finish time.

3.  Add subtitle to MKV file
If your MKV subtitle is seperated, you may want to add it to the MKV file.

Step 1 Put your MKV subtitle in the same folder with MKV video and name as the MKV.
ie. D:\Movie\chd-ntbos-bdrip.mkv   D:\Movie\chd-ntbos-bdrip.srt

Step 2 Then select "Add" button to load the MKV video files, this tool will detect your subtitle file and add subtitle automatically.

Link
MKV Splitter