Most of the features included in MPEG-4 are left to individual developers to decide whether to implement them. This means that there are probably no complete implementations of the entire MPEG-4 set of standards. [...
MPEG-4 consists of several standards—termed "parts"—including the following: [a list of 28 different standards follows] [...
Licensing
MPEG-4 contains patented technologies that require licensing in countries that acknowledge software algorithm patents. Patents covering MPEG-4 are claimed by over two dozen companies. The MPEG Licensing Authority[61] licenses patents required for MPEG-4 Part 2 Visual from a wide range of companies (audio is licensed separately) and lists all of its licensors and licensees on the site. New licenses for MPEG-4 System patents are under development[62] and no new licenses are being offered while holders of its old MPEG-4 Systems license are still covered under the terms of that license for the patents listed (MPEG LA – Patent List).
AT&T is trying to sue companies such as Apple Inc. over alleged MPEG-4 patent infringement.[63] The terms of Apple's Quicktime 7 license for users[64] describes in paragraph 14 the terms under Apple's existing MPEG-4 System Patent Portfolio license from MPEGLA.
What does this mean for you? (A) That you need a top-quality patent lawyer if you want to even look at the MPEG code, as you may be accused of patent infringement for using old well-known techniques that some company has attempted to patent; and (B) you better have financial resources as large as Apple's read to fight the legal battles.
I know that I cannot afford to have myself or the organization I work for accused of patent violations by companies that have not even come forward yet to state their patent claims, so I actively avoid working in this field. If I were given a school assignment to work in the field, I would demand that the school either change the assignment or agree in writing to shield me from any patent litigation that might come out of the work they are requiring be done.
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