Audio-only when in background

**Topic**
Please select what topic your discussion is about.
- [ ] Coding
- [ ] Contribution
- [ ] Languages
- [ ] Setup
- [x] Other. Please specify: Format and Video Play

**Discussion**
Here is the thing:
Many people let videos play in background (e.g. while doing other things).
This is a waste of bandwidth and energy (remember climate change etc.).
Even though it is of course possible (e.g. for Music Videos) to play them enterily in the audio-only stream, sometimes there are videos that people still also want to look at (from time to time).

Now my theoretical idea is that FreeTube could offer an option in the settings, to always switch to the audio-only stream when the video is in background for a longer period of time (e.g. longer than 30 seconds) and then switch again to the regular video format when the viewer looks at it again/the freetube window is in focus again.

There is one potential problem I see though:
Is the buffering/loading time between the switches maybe too long? So it would be actually too annoying for the user?

I am interested in your oppinion about this :slightly_smiling_face:.