MKV and M4V are containers. They hold separate video, audio and subtitle tracks. Moving suitable tracks into another container is called remuxing; it does not require decoding and re-encoding the picture.
Try a compatible-video workflow
- Add the MKV file and check its metadata.
- Select Apple compatible.
- Review the audio and subtitle tracks and choose the destination.
- Leave source deletion disabled for the first test, then start processing.
- Check the finished M4V in your intended player.
iFlicks can directly copy suitable H.264 or HEVC video when the track is muxable and within the selected preset's limits. Other sources or settings can require a new video encode. A resolution or codec change can also change the processing path. The MKV extension alone does not tell you which path is possible.
What does lossless mean here?
Direct video copying avoids additional picture-quality loss from another video encode. Audio may still be converted, and subtitle handling depends on its format. Remuxing therefore does not mean every track or the entire file remains byte-for-byte identical.
Duration and output size can give useful clues, but neither proves that the video was copied. If you need help establishing why a particular file is being encoded, include the source-track information, chosen preset and diagnostic log in a support request.