Another thing to add: weight for vinyl. Some fancy reissues will use 180g, 200g, etc vinyl. I don't know if this is actually better or not than the normal weight.

This is a great addition! I think, though, that if you offer the option of adding colors, it should be done with a HEX color picker. Descriptions are misleading and people have different opinions of what colors are called (sometimes labels make up color names to sound fancy). With a color picker, one could easily match the color of the medium to the color on the screen and that could be displayed next to the format type.

For user interface, it might be helpful to offer the different branding logos of the more common mediium types:  CDDA logo, CDDA+ logo, HDCD logo, DVD logo, Enhanced CD logo, blu-spec logo, xrcd logo, Blu-Ray logo.  There might be others. Links in the web interface to (for example) a wikipedia page for that logo/medium type would help.

Short instructions to users would be "select this medium if you see the logo on your release" with a short menu list including the logos for first level.  I think that would capture most of the edits and hopefully the rest can figure it out from experience and further detailed instructions in further menu levels.  Long instructions would have to get into more info about types and uses and how to figure it out for edge cases.

Is it through this attribute system that we would be able to say, this DVD is region 2, DVD-5, DVD-9, double sided (with both side not necessarily same DVD-5/9), etc. ?
4:3 and 16:9 and PAL, etc. are more recording attributes maybe, as they can vary inside the DVD (aspect ratio often varies but PAL/NTSC variations, although possible (per title), that would surprise me.
Sound (AC3, LPCM, MPEG) and video format would also be something at the recording level.

How well could this schema accommodate dual or hybrid medium format like:

Hybrid SACD (CD layer)
Hybrid SACD (SACD layer)

DualDisc (CD side)
DualDisc (DVD side)

DVDplus (CD side)
DVDplus (DVD-Video side)
DVDplus (DVD-Audio side)

Could we have here a medium format attribute whose type would be a medium format?
Some kind of recursive definition?

See also http://tickets.musicbrainz.org/browse/STYLE-381

Just wanted to add that I am really, really against adding such attributes as bitrate or format (mp3, m4a, flac) to digital releases, and I'm sure many others share this thought. So such a change should be discussed on -style rather than on this ticket, and not be considered an implementation detail, since it would dramatically affect the dataset.

@Kuno Woudt: I don't disagree completely, but I tried to find a set of attributes which were as broadly-applicable as possible. I may have failed in that some attributes (speed, size/diameter only apply to some media), but whatever we would call that attribute ("compression"?) only applies to a relatively small subset of the media types (digital media) or is otherwise tangled up with the medium format itself (e.g. Dolby DSD is exclusive to Super Audio CD, as far as I know).

If we do store the format of media releases, we'll want to have very clear guidelines on when to accept what.

@alex mauer: I definitely want us to store at least mp3, m4a, flac – this shouldn't be a problem if we allow multi-selects.

@lixobix: I considered this when creating the proposal, but there are two problems with that.

First, we don't generally store separate releases for different codecs/bitrates (think of the explosion of bandcamp releases alone, if we did).

Second, I thought about doing adding attributes bit depth, sample rate, channel count, and codec (mostly for digital releases). However, it quickly became clear that it just wouldn't work that well, mostly because there is a rapid explosion in the number of attributes, and there isn't much need for them.

@HibiscusKazeneko: Do we actually have any VHD releases in the database?