www.makemkv.com

I keep seeing people claim to be able to change the file container on mkv files super quickly. 10-20 minutes. Maybe I’m missing something, but I’m using Xmedia recode and it looks like it will take four hours for a 55gb file?

Converting a file depends on what you're intending to do with it. Going from MKV to "something else" depends upon whether or not the video is compatible with "something else".

Plex will handle MKV just fine…

I use Handbrake to convert MKV to MP4.

https://handbrake.fr/

A Matroska (.mkv/.mk3d/.mka/.mks) file is a 'container', it can contain various types of video tracks encoded with a multitude of codecs, some may be mpeg2, or mpeg4, or VC-1 (the three main codecs used in Blu-rays), or any number of others. And .mkv files commonly contain multiple video, audio, and subtitle tracks, as well as multiple editions of chapters.

So talking about "converting" .mkv to .mp4 is like saying you're converting a car to a particular type of passenger, one only 'contains' the other and the contents vary greatly.

As @Sunoo said above, I use .mkv files exclusively on my Plex server and I've never had an issue.

@andres42: It depends on what you're trying to change about the file container and what it contains. MKVToolNix can change certain attributes without re-muxing the file, but from the timeframe you mentioned it sounds like you may be talking about re-encoding the file?

If the .mkv container already contains a .mpeg4 file, then you're re-encoding for nothing!

If the .mkv has a video track encoded using a codec that your Plex player doesn't like, that's when you may need to re-encode, and the time that takes depends entirely on the hardware you're using. If you have a gaming PC with a heap of high-end GPUs installed it may take only minutes to do what an old core-duo CPU takes hours to do!