Some of the videos in realMyst Masterpiece Edition suffer from repeated conversions into different formats for different editions of Myst and have ended up lower quality than they could be.
I've put together a patch that replaces the videos of Sirrus, Achenar and Atrus with higher quality ones.
For Sirrus and Achenar, the new videos are from Myst Masterpiece Edition. These videos are supposed to be fuzzy anyway but the new ones are sharper and have much better audio.
For Atrus, the new videos are from realMyst and are twice the resolution.

Download the patch for v2.2 here: Mac instructions:
Right-click the "Apply Patch.command" file and choose Open. This shell script will try to automatically find your realMyst app and use the included bspatch tool to apply the two patch files.

Windows instructions:
Run the program and follow the steps. Make sure you select your realMyst installation directory (typically C:\GOG Games\Real Myst Masterpiece Edition).

I used the Unity Assets Bundle Extractor tool to modify the assets files. For reference, the following assets have been modified (Path ID and Name)...

resources.assets:
1628 AchenarExtra
1615 AchenarPage0
1626 AchenarPage1
1642 AchenarPage2
1619 AchenarPage3
1637 AchenarPage4
1612 AchenarPage5
1618 AtrusBook1
1622 AtrusBook1_Loop
1630 AtrusBook2
1625 AtrusBook2_Loop
1621 SirrusExtra
1635 SirrusPage0
1620 SirrusPage1
1631 SirrusPage2
1623 SirrusPage3
1632 SirrusPage4
1616 SirrusPage5

sharedassets1.assets:
6081 AchenarLose
6168 AchenarLose
6086 SirrusLose
6172 SirrusLose

I can't get your patch to work on Windows. I downloaded a different copy of bspatch and was able to get the patch to complete. When I launch the game the intro video is just a pink screen.

So I did the patch on the Mac version successful and didn't have any issue with the video. Wasn't able to play far into the game due to not having a good enough GPU to put up with the framerate. I took the patched files and copied them to my PC, but I still had issues with textures and normal maps being corrupted although the intro video played fine. I'd be open to replacing the videos manually if the original author wants to share the method.

The poor quality videos don't break the game but its a shame there wasn't an attempt to get them looking as good as possible. Real Myst Masterpiece seems to have not had the initial care and detail as some remasters do.

Sorry about this guys, I admit I've only tested the Mac version - I assumed the data files would be the same for the Windows version.

If you're wanting to try it yourself, you'll need the following utility to edit the .assets files: neohx_7, you may need to inspect the patched Mac data files first so you can extract the modified assets, then try putting them into the Windows data files.
If I remember correctly, the modified videos are...
resources.assets: 4 Atrus videos, plus Sirrus/Achenar "lose" videos.
sharedassets1.assets: Sirrus Achenar page videos (0-5 plus "extra")
Some of the videos include the audio track, some of them have a separate audio track (I forget which ones are which).

If I get time I'll try take a look at the Windows version myself.

I've finally got around to the Windows version and confirmed that the data files are sadly not identical. So I've had to separate the patch into Mac and Win versions, which you can now find at the top. The Win version is a stand-alone patch tool created by the Unity Assets Bundle Extractor, so it should be real easy to use.