There are many ways to extract .srt from any videos.

1. A tool that analyzes video files and produces independent subtitle files from the closed captions data. CCExtractor is portable, small, and very fast. It works in Linux, Windows, and OSX.

2. Free download the ideal MKV Subtitle Extractor for Windows or Mac - iDealshare VideoGo , install and run it.

• Then Click"Add File" button to add the MKV video from which you like to extract subtitles as .srt. Or simply drag and drop the MKV to the main window of this MKV Sub Extractor.
• After that on bar Select File --> Properties... to open the Properties window.
• In the "Properties" window, look for the type "Subtitle". Then click the "Save As" button on the right side of your preferable subtitle to choose which folder will store the subtitles. Then this ideal MKV Subtitle Extractor will automatically save this subtitle as .srt to your selected folder.

3. Try paid service with: http://subtitlevideo.com

Hope you like it….