Use MP4 to MKV - free
Frequently asked questions
Does this re-encode my video?
No. MKV supports the same H.264/AAC codecs MP4 uses, so this just repackages the file into a new container.
Why use MKV over MP4?
MKV is popular for archiving and home media servers since it supports multiple audio tracks and subtitles more flexibly than MP4.
Is there any quality loss?
No, since no re-encoding is needed, quality is identical to the source.