[Ffmpeg-devel] Re: Re: [PATCH] x264 avc encoding, movenc avcC, ctts

[Richard S.]

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 instance one of them is obsolete, I'd vote for adhering to the current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