[Ffmpeg-devel] Re: Re: [PATCH] x264 avc encoding, movenc avcC, ctts (original) (raw)

Richard S. teetrinker
Mon Feb 20 14:07:38 CET 2006

bond schrieb:

I got here a sample produced by FCP which does not contain 'iods' atom. I consider FCP being the reference, so 'iods' is not needed when 'mp42' ftyp is used. Are all of "isom"/"mp42"/"mp41" completely valid mp4 types? If for instance one of them is obsolete, I'd vote for adhering to the current standard (be it "isom" or "mp4.")

mp41 is for the old first version of the MP4 specs so not useable anymore (14496-1), mp42 is for 14996-14 as its now (eg asp/aac streams in mp4), avc1 brand is for 14496-15 files (avc in mp4), isom brand is for everything that said i would use "mp42" for aac/aac files and "avc1" for avc files iods is definitely not needed for avc mp4 files and regarding part2 files needed for isma compliance (which noone cares about/needs). if its easy to write an iods atom than why not simply write it always (or never?). i dont know any player that needs the iods atom btw (and i tested nearly all mp4 players/parsers available on windows) ISMA 1 included IOD and BIFS/OD track to be compatible with a Mpeg 4 SYSTEMS player. about the bifs/od, its a hard task to implement correct (!) ones of those. also as no player cares about those and as they are not mandatory, i would also simply not waste my time on making these work if you still want to check how a correct bifs/od should look like, check the ones mp4box writes Osmo4(GPAC) cares about BIFS/OD. If there is a BIFS/OD track, Osmo4 will render the MP4 file according to the BIFS/OD track. But like bond said it is not easy to implement. I would use "isom" or maybe "avc1" for the major brand(avc1 have to be in the compatible brands). But keep in mind that isom/avc1 normally shouldn't be used for the major brand.

I would use "mp42" only if there is a correct IOD and BIFS/OD track. It is true that most Players don't care for IOD and BIFS/OD, but a MP4 file conformance to 14496-14 should have a IOD and BIFS/OD Track. If you have only a simple audio/video file there is no problem, but if you got a file with a complex scene it will be rendered wrong, by a player which don't take BIFS/OD into account.

If you don't like IOD and BIFS/OD use a 3gp file with ftyp "3gp6" or use H.264 in mov with ftyp "qt ".

This is my opinion to the major brand. Richard

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