Is there an optimal way to preserve quality when translating file formats?

Question

My screen recording software, OBS, seems to encourage recording in MKV. My video editing software, DaVinci Resolve 18, doesn't support this format on Linux (as far as I can tell). The options I have (that I know of) are:

1. Record in another format.
2. Record in MKV and convert.

I would guess that (1) is always better, since I imagine converting always entails some amount of degradation or file size inflation over the native format. But then again, I could imagine that OBS is optimized somehow for MKV.

So that's basically my question, in this case and in general: Is it always better to avoid conversion, or are there situations when you actually get better quality video by recording in one format and then converting?

Answer 1

A .mkv file is video and audio inside a Matroska Multimedia Container. The Matroska part is, just like the name implies, the outer bits that hold the essence streams, the actual audio and video. The essence will be compressed (for the video and, occasionally, the audio) or encoded (for the audio, usually) in their own formats. Something like H.264 for the video and linear PCM for the audio.

You can use ffmpeg or a similar tool to re-wrap the essence into another container that Resolve supports. Re-wrapping from one container to another is loseless because you don't actually change the video or audio, just how you access it. You will most likely want to use an MPEG-4/.mp4 or Quicktime/.mov container, but it depends on what your video codec is.