Before learning how to convert MP4 to MKV, it is necessary for you to know about the term MKV.
What is MKV?
MKV is a container for the video data. Thus, MKV can contain data from several different types of encodings (or codecs) for video, its greatest usefulness is the synchronization of video data with audio, with the titles and subtitles etc.
If you want to convert MP4 to MKV, MP4 to MKV Converter - a part functions of AVS Video Converter, is your best choice, download it and have a try! and you will feel how powerful the MP4 to MKV Converter is.Step 1: Add MP4 files
After the installation job is done, start it, just click "Browse..." button circled to select MP4 as your input.

Step 2: Settings
Click "To MKV" button and "Advanced>>" button to set the detail output format. Specify a output folder by clicking the other "Browse..." button.

Step 3: Start converting MP4 to MKV
Click "Convert Now!" button on the right at the bottom of the interface to start MP4 to MKV convert.
The Video Converter helps you easily convert MP4 to MKV, and convert MP4 to MOV. What is more, it also can convert between most popular video formats. Download the MP4 to MKV Converter, and enjoy the other powerful function of the software.