bjs;665789 Wrote: > Interesting news: > http://www.tuaw.com/2011/10/27/apples-alac-codec-is-now-open-source/Unfortunately > I think there is still a part of this story missing...
Apple .M4A music files consist of a raw data music stream, that is wrapped inside an ISO MPEG4 file container. MPEG4 is an open ISO standard that defines a nestable structure of "boxes", where each such box has a name, and a predefined data payload. The ISO standard specifies some of the standard box names and their respective payloads. But the standard is extensible and allows vendors to add their own box definitions, and define their respective payloads. This works fine, because if a particular client does not understand the contents of a particular box type, it can ignore it and jump over to the next box. One such standard MPEG4 box is the music stream box; it may contain MP3, MP4, AAC, ALAC or proprietary raw stream data. Therefore it is of course excellent news that Apple has open sourced the ALAC format, because it increases the number of public domain raw data stream payload formats that the standard MPEG4 music stream box can carry. BUT, Apple still still uses other (proprietary) boxes to carry the track meta-data (i.e. the tags). These Apple proprietary metadata boxes obviously fit within the overall ISO format, and their names are known, and their payload structures have been reverse engineered. (So for example the SBS Scanner knows how to parse the tags). HOWEVER, so far as I know, these meta data tags have NOT been open sourced by Apple, so they could change the payload structures at whim, and thus "break" any third party applications that rely on them... => Dear Apple, please also open source your meta data boxes!! -- AndrewFG Regards, AndrewFG Try out Whitebear. The middleware that joins the two worlds of: 1. UPnP/DLNA media clients and media players, and, 2. Squeezebox Server and Squeeze Players Download it for free here: http://www.whitebear.ch/mediaserver ------------------------------------------------------------------------ AndrewFG's Profile: http://forums.slimdevices.com/member.php?userid=15838 View this thread: http://forums.slimdevices.com/showthread.php?t=91185 _______________________________________________ discuss mailing list discuss@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/discuss
