ios - Understanding ISO mp4 m4a Metadata -

ios - Understanding ISO mp4 m4a Metadata -

i unable find specification understand metadata m4a file.

this not beingness copied across avassetexportsession , wanted manually read , write info exported file.

this see in debugger

avmetadataformatisouserdata;

2014-10-22 16:19:33.496 mobile magnet[189:15972] 1835365473, <avmutablemetadataitem: 0x17e7de00, identifier=uiso/meta, keyspace=uiso, key class = __nscfnumber, key=meta, commonkey=(null), extendedlanguagetag=(null), datatype=com.apple.metadata.datatype.raw-data, time={invalid}, duration={invalid}, extras={ datatype = 0; datatypenamespace = "com.apple.quicktime.udta";

}, value=<00000000 00000022 68646c72 00000000 00000000 6d646972 6170706c 00000000 00000000 00000000 0166696c 73740000 00bc2d2d 2d2d0000 001c6d65 616e0000 0000636f 6d2e6170 706c652e 6954756e 65730000 00146e61 6d650000 00006954 756e534d 50420000 00846461 74610000 00010000 00002030 30303030 30303020 30303030 30383430 20303030 30303144 30203030 30303030 30303030 39413131 46302030 30303030 30303020 30303030 30303030 20303030 30303030 30203030 30303030 30302030 30303030 30303020 30303030 30303030 20303030 30303030 30203030 30303030 30300000 00a22d2d 2d2d0000 001c6d65 616e0000 0000636f 6d2e6170 706c652e 6954756e 65730000 00146e61 6d650000 00006954 756e4e4f 524d0000 006a6461 74610000 00010000 00002030 30303031 32424620 30303030 31343139 20303030 30364533 36203030 30303830 32302030 30303241 31363120 30303033 34364432 20303030 30383230 42203030 30303831 36392030 30303244 38383720 30303033 30434335>> },

this

}, value=<00000000 00000022 68646c72 00000000 00000000 6d646972 6170706c 00000000

looks name atom (or block) in mp4 container. i've seen 5th through 12th bytes in file made yamb , on atomicparsley page.

ios osx metadata itunes mp4