Well, there seem to be a number of questions:
1) How is "virtually any codec" implemented?
MXF is a wrapper or container format; it can contain an almost unlimited variety of things (AVI is also a wrapper/container format). The codec handling is up to the application that encodes or decodes the files.
2) Does MXF support something like FOURCC?
Yes, essence format is identified by a 16-byte SMPTE UL.
3) Is it possible to use a proprietary codec of uncompressed format such as RGB?
Yes, as long as there is a UL that can be used to identify your format (I assume you are talking about the essence format rather than the specific software or hardware used to encode and decode it) then it can be wrapped in MXF. This UL needs to be registered with SMPTE as they maintain the global register of these values. Many essence formats already exist in the register - usually with a standard that describes the format in detail. Uncompressed RGB is one of the basic ones that was there from the start.
4) Is MXF an open standard?
This depends what you mean by "open standard". There is no fixed definition of this term. It is not "free" and it is copyrighted. It took many hundreds of man-years to produce and involved a significant amount of input from some of the largest broadcast companies on the planet, however the documents are available for a relatively reasonable cost to anyone that wants to buy them and most of them are totally royalty free (in fact as far as I am aware the only royalties anywhere in the who standard are those involved in encoding or decoding some of the proprietary essence formats such as h.264)
You can find the individual documents in the
SMPTE store - if you want many of them it is worth buying the CD-ROM
5) If it is not freely available how come it was chosen for Digital Cinema by DCI?
I assume by this you mean if it was not "free".
This may be an overly simplistic explanation, but:
http://en.wikipedia.org/wiki/Digital_Cinema_Initiatives wrote:
The organization was formed in March 2002 by the following studios:
* Metro-Goldwyn-Mayer
* Paramount Pictures
* Sony Pictures Entertainment
* 20th Century Fox
* Universal Studios
* The Walt Disney Company
* Warner Bros.
The entire CR-ROM of over 600 SMPTE standards costs $500. I don't think that any of these companies are that concerned about needing to spend $500 to get the documents necessary.
