[FFmpeg-devel] [PATCH] mp4 and ipod metadata

[Michael Niedermayer]

On Fri, Jun 13, 2008 at 09:14:13PM -0700, Baptiste Coudurier wrote:
> Michael Niedermayer wrote:
> > On Fri, Jun 13, 2008 at 02:26:24PM -0700, Baptiste Coudurier wrote:
> >> Baptiste Coudurier wrote:
> >>> Michael Niedermayer wrote:
> >>>>>> [...]
> >>>>>>
> >>>>>> And above all even if no spec defined it, that would not affect that
> >>>>>> its default value of 2 would be valid for all specs then (as none
> >>>>>> defined it otherwise).
> >>>>>> Its kinda simple either one defines it or none defines it. Either way
> >>>>>> there the incompatibility you claimed does not exist.
> >>>>>> Whats even more ridiculous is that you insist to only support a ancient
> >>>>>> revission of the 3gp spec because the later REQUIRE all 3gp files to
> >>>>>> claim to be iso media compatible. And you seem to prefer if they are
> >>>>>> not compatible.
> >>>>> This is false. 
> >>>> what is false?
> >>> That I insist to only support an ancient revision. I dont prefer them
> >>> not being compatible, I'm definitely ok to put 'isom' in compatible
> >>> brands, and as much compatible brands that it is possible.
> >>>
> >> Here is an attempt, I may have overlooked things.
> > 
> > This patch changes quite a lot of things at the same time ...
> > 
> 
> Yes. I'll split the commits.
> 
> > 
> >> +        if (codec_get_tag(codec_3gp_tags, st->codec->codec_id))
> >> +            has_3gp_tags |= 1<<i;
> > 
> > will fail with >32 streams
> 
> Damn. Ok.
> 
> >> [...]
> >>  
> > 
> >> @@ -1407,18 +1414,18 @@
> >>      if(mov->mode != MODE_MOV){
> >>          put_tag(pb, "isom");
> >>          put_tag(pb, "iso2");
> >> -    }
> >> +        if(has_h264)
> >> +            put_tag(pb, "avc1");
> >> +        if(mov->mode != MODE_PSP){
> >> +            if(has_3gp_tags == (1<<s->nb_streams)-1){
> >> +                put_tag(pb, has_h264 ? "3g2b":"3g2a");
> >> +                put_tag(pb, has_h264 ? "3gp6":"3gp4");
> >> +            }
> > 
> > This is incorrect, as an example why, lets consider a video stream and
> > 2 audio streams. One which is allowed in 3gp6 and one which is allowed in
> > mp41. The file is clearly compatible with both not with none.
> > (ignoring the missing tracks issue for the moment)
> 
> What I found:
> In 3gp Release 5:
> 
> "- the maximum number of tracks shall be one for video, one for audio
> and one for text;"
> 
> 3GPP TS 26.234 V5.7.0 (2005-03), yes, dates are really wierd.
> 
> this is not mentioned for 3gp Release 4 however, but,
> 
> in latest 3GPP TS 26.244 V7.3.0 (2007-12):
> 
> "NOTE 1:
> The Basic profile of 3GP in Release 6 and 7 corresponds to 3GP files of
> earlier releases, which did not define profiles. Files with brands
> ?3gp4? and ?3gp5? in Release 4 and 5, respectively, correspond to files
> with brand ?3gp6? in Release 6 and ?3gp7? in Release 7."
> 

> Also in 3GPP2 C.S0050-B:
> 
> "Conditions for using 3GPP branding are that the media types contained
> in the ".3g2" file are restricted to those identified for use in the
> ".3gp" file format [5]."
> 
> So 3GPP2 disagrees with you it seems.

yes


[...]
> 
> Also:
> 
> "5.5	File-branding guidelines
> 
> [...]
> 
> -	that a reader implementing that specification (possibly only that
> specification) is given permission to read and interpret the file."
> 
> If we put codecs not supported, the reader will not be given permission
> to read the file IMHO.
> 
> "All 3GP files of Release 5 or later shall contain the compatible brand
> ?isom? indicating that they conform to the ISO base media file format,
> unless the reader is required to interpret extensions specific to the
> AVC file format [20], for which case the compatible brand ?avc1? shall
> be used instead (see note 2)"
> 

> Seems if we want to force the player to be able read H.264 track it
> seems with must not put "isom". Do we want ? He might still read the
> audio track.

hmm, i would vote for leaving isom in there
being able to listen to the audio of a music video is nice by itself.


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I count him braver who overcomes his desires than him who conquers his
enemies for the hardest victory is over self. -- Aristotle
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