How to Convert M2TS to MKV File?

Why somebody want to convert M2TS to MKV? Maybe because of the file size. A M2TS file taken from a Blu-ray or AVCHD disc is going to be a bit bigger than an MKV with the same contents, because the M2TS contains extra file structure information you don't need. MKV has less overhead than M2TS so a 1: 1 copy would be a little smaller. People usually remove some audio streams and subtitles they don't need, and the output MKV file would be smaller in size.
Stick with below steps to convert M2TS to MKV:
1: Add Source M2TS Files
After install Video to MKV Converter, first we are going to load M2TS files into the program. You may get M2TS files from HD video camera or camcorder. This converter supports batch conversion, and you can import several files at one time.
2: Set Output Format
Click "Profile", there are various output video formats, select "MKV (Matroska) Video (*. mkv)" for your device.

In order to set advanced audio and video parameter, please click "Settings". Here you can set video size, frame rate, aspect ratio, audio channel etc. Basically the M2TS is a typical HD video format with very high video and audio quality, normally in 16: 9 aspect ratio. In order to avoid stretched image, you are advised to set 1920*1080 or 1280*720 as video size. But if you'd like to change the 16: 9 video to 4: 3 for standard definition conversion, choose 640*480 in the dropdown list of "Size".
3: Edit your M2TS Files (Optional)
This application can help you crop and trim video, set brightness, contrast, saturation as well as add watermark before the conversion.

4: Start Convert M2TS to MKV
Press Convert button to begin the conversion to M2TS to MKV automatically.