[FFmpeg-devel] [PATCH] mp4 and ipod metadata
Thu Jun 12 20:49:39 CEST 2008
On Thu, Jun 12, 2008 at 11:35:18AM -0700, Baptiste Coudurier wrote:
> Michael Niedermayer wrote:
> > On Thu, Jun 12, 2008 at 10:13:49AM -0700, Baptiste Coudurier wrote:
> >> Hi Michael,
> >> Michael Niedermayer wrote:
> > [...]
> >>> Additionally 3gpp says: ----------------------- The file-type brands
> >>> defined in this specification are used to label 3GP files belonging
> >>> to Release 6 and conforming to one or more profiles. 3GP files may
> >>> also conform to earlier Releases or even to other file formats, such
> >>> as MP4, which is also derived from the ISO base media file format
> >>> . Table 5.1 contains a non-exhaustive list of examples with 3GP
> >>> files for various purposes. All 3GP files of Release 5
> >> AFAIK We are using Release 4 !
> > release 4 is from 2000/2001
> > I really think we should try to be conformant to a recent version of it!
> > Especially if one considers that the mp4 and iso base formats arent
> > that old themselfs.
> > Iam a little puzzled why you refuse to accept the more recent versions.
> > Versions that clarify that iso base compatibility and thus a valid
> > channel count is mandatory.
> What about old devices ?
No device reads and depends on a reserved field that contains no
> Should we drop old features like psp atoms
> because new firmwares work without it ? No.
no of course not
> > Besides id like to repeat that you ignored my objections to the change
> > of the channel count to a fixed 2.
> > So I request that this change is reverted, unless you can show that it
> > has to be 2 for some demuxer hardware of software.
> All software I know put 2 here (including gpac which is a very strong
I do not care at all if all software violates the specs.
> MPEG-4 says template field has to be used:
> "In MPEG-4 both visual and aural composition are done using the BIFS
> system. Therefore structures marked as ?template? in the ISO Base Media
> Format which pertain to composition, including fields such as matrices,
> layers, graphics modes (and their opcolors), volumes, and balance
> values, from the MovieHeaderBox and TrackHeaderBox, are all set to their
> default values in the file format.
> These fields do not define visual or audio composition in MPEG-4; in
> MPEG-4, the BIFS system defines the composition."
> Are you stubborn or ?
No but you quote mpeg4 systems, neither 3gp nor the iso base claim to be
compatible with mpeg4 systems.
We arent storing BIFS last time i checked and most important
"Therefore structures marked as ?template? in the ISO Base Media
Format which pertain to composition, including fields such as matrices,
layers, graphics modes (and their opcolors), volumes, and balance
values, from the MovieHeaderBox and TrackHeaderBox,"
does NOT cover channel count in any way no matter what part of this
sentance you consider. channel count is not in MovieHeaderBox nor
TrackHeaderBox nor does it pertain to composition.
> 3gp specs mandates value 2 for this field, like I proved many many times.
3gp release 5 and later mandate iso media compatiblity that mandates this
value to be 1 for mono streams beyond doubt.
all 3gp specs ive seen mark the field as reserved not fixed=2. reserved is
not the same as fixed. A demuxer depending on the value of a reserved field
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
I am the wisest man alive, for I know one thing, and that is that I know
nothing. -- Socrates
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