The initial near-complete MPEG-1 standard (parts 1, 2 and 3) was publicly available on 6 December 1991 as ISO CD 11172. In most countries, patents cannot be filed after prior art has been made public, and patents expire 20 years after the initial filing date, which can be up to 12 months later for filings in other countries. As a result, patents required to implement MP3 expired in most countries by December 2012, 21 years after the publication of ISO CD 11172. COUNT 5
QSN1 What became publicly available on 6 December 1991? ANS1 MPEG-1 standard QSN2 When can patents not be filed in most countries? ANS2 after prior art has been made public QSN3 How long does it take for patents to expire after being filed? ANS3 20 years QSN4 How long can it take for patents to be approved after initially being filed? ANS4 12 months QSN5 When did patents required to implement MP3 expire in most countries? ANS5 December 2012