I have some features request on the new release of the codec: firstly, file previews. For the 8-bit files (both YUV and RGB(A) as far as I've tried) previews work just fine, just as you'd expect; for 10/12/14 bit files, previews don't work, you just see the "video" icon (or in my case the VLC icon). Of course it's not a dealbreaker, but it'd be nice if solved. The second request I have is some sort of "dictionary" implemented in the codec itself that tells QT which preset you chose when encoding the file, to distinguish between YUV (444, 422, 420, 400), RGB(A) and different bit depths. With "dictionary", I mean the actual name corresponding to the format ID that you can see with a program like MediaInfo, which (as you can see in the image) tells you only the format ID instead of a "full and understandable" name.
About preview: the reason it's missing is that the preview generator in the OS probably requests 8-bit RGB, and the deep-color codec variants deliberately refuse to decode as 8-bit to prevent accidental conversions to 8-bit, which would defeat the whole purpose of the deep color codecs. I might try to look into somehow distinguishing when it is requested for preview, but that's just hacking and errorprone. Do you mean the "Windows file explorer" preview btw? Actually, I don't see thumbnails at all for any kind of .mov file.
About the dictionary: I don't know where does MediaInfo get that info from, isn't that something hard-coded into MediaInfo itself? For the time being, you can use the fourcc (Codec ID) to distinguish between variants, each variant uses a separate fourcc:
MAGY: MagicYUV Decoder (Generic) or fourcc used by the old (1.2) version
M8RG: MagicYUV - RGB
M8RA: MagicYUV - RGBA
M8YA: MagicYUV - YUVA 4:4:4:4
M8Y4: MagicYUV - YUV 4:4:4
M8Y2: MagicYUV - YUV 4:2:2
M8Y0: MagicYUV - YUV 4:2:0
M8G0: MagicYUV - YUV 4:0:0 (Greyscale)
M0RG: MagicYUV 10-bit RGB
M0RA: MagicYUV 10-bit RGBA
M0Y2: MagicYUV 10-bit YUV 4:2:2
M0G0: MagicYUV 10-bit YUV 4:0:0 (Greyscale)
M2RG: MagicYUV 12-bit RGB
M2RA: MagicYUV 12-bit RGBA
M4RG: MagicYUV 14-bit RGB
M4RA: MagicYUV 14-bit RGBA
The preview I mean is the Windows Explorer one: as far as I understood when I searched for it some time ago, it asks the default application (in my case VLC) to generate the preview. Depending on the Advanced system settings, the Explorer settings and the Windows Registry it may or may not generate previews all along. And now that I understand the reason why it doesn't generate them it's not a big deal, because it's not essential for me to have them.
About the codec ID, on the fourcc website, MediaInfo is one of the recommended application to identify the codec's ID, name and properties: this time it's really important for me to be able to differentiate between different bit depths and chroma subsamplings, but now that I looked at the " dictionary" you posted I see the pattern you used for the IDs, so from now on I can't go wrong. Thanks anyways for the reply and informations!