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Microsoft also supports MP3 on its Zune mobile player.

The case appears to illustrate a problem with patent licensing: just because you obtain the rights to use a certain technology, can you be sure that it is possible to implement it without infringing another patent?

To give a trivial and fictitious example, a licence to paint signs on walls might be of limited value if another party has patented the process of putting paint on walls.

Both Bell Labs and Fraunhofer were involved in the development of the MP3 technology, and the former is now part of Alcatel-Lucent. Several key technologies have emerged from Bell Labs, including the transistor, cellular telephony, lasers and Unix.