Editing Dolby Digital (section)

== License ==

AC3 was covered by patents that expired in March 2017. Patents were used to ask to pay a commercial license to publish an application that decodes AC3. This led some audio app developers to ban AC3 from their apps, although the open source [[VLC media player]] supported AC-3 audio without having paid a patent license fee.<ref>{{cite web|url=http://www.videolan.org/vlc/features.html|title=VideoLAN – VLC – Features|last=VideoLAN|access-date=1 January 2017}}</ref>

In Dolby's 2005 original and amended S-1 filings with the SEC, Dolby acknowledged that "Patents relating to our Dolby Digital technologies expire between 2008 and 2017."<ref>{{cite web|url=http://dlb.client.shareholder.com/secfiling.cfm?filingID=1193125-04-200308&CIK=1308547|title=SEC Form S-1|publisher=ADOBE investor relations website|access-date=2017-03-22}}</ref><ref>{{cite web|url=https://www.sec.gov/Archives/edgar/data/1308547/000119312504200308/ds1.htm|title=SEC Form S-1|publisher=United States Securities and Exchange Commission (SEC) EDGAR system, filed November 19, 2004|access-date=2017-03-22}}</ref><ref>{{cite web|url=https://www.sec.gov/Archives/edgar/data/1308547/000119312504221162/ds1a.htm|title=Amendment No. 1 to SEC Form S-1|publisher=United States Securities and Exchange Commission (SEC) EDGAR system, amended February 12, 2005|access-date=2017-03-22}}</ref>

The last patent covering AC-3 expired March 20, 2017, rendering it free to use.<ref>{{cite web|url=https://news.ycombinator.com/item?id=13910925|title=The last patent on AC-3 (Dolby Digital) expires at midnight {{!}} Hacker News|website=news.ycombinator.com|access-date=2017-05-06}}</ref><ref>{{cite web|url=https://ac3freedomday.org/ |archive-url=https://web.archive.org/web/20170319195106/https://ac3freedomday.org/ |url-status=usurped |archive-date=March 19, 2017 |title=AC3 Freedom Day – s |publisher=Ac3freedomday.org |date= |accessdate=2022-02-17}}</ref>

=== Open source implementation ===
A free ATSC A/52 (AC3) stream decoder, [http://liba52.sourceforge.net/ liba52], is available under the [[GNU General Public License]]. [[FFmpeg]] and the VLC media player each include code for handling AC-3.