[FFmpeg-devel] [PATCH 1/1] avformat/movenc: use modern iTunes copyright atom

[Michael Niedermayer]

On Mon, Apr 02, 2018 at 12:02:38PM +0300, Timo Teras wrote:
> On Fri, 30 Mar 2018 04:06:03 +0300
> Timo Teras <timo.teras at iki.fi> wrote:
> 
> > On Fri, 30 Mar 2018 02:39:13 +0200
> > Michael Niedermayer <michael at niedermayer.cc> wrote:
> > 
> > > git log points to
> > > bed4fc54c947b9e36d2103b400d438bfb4dd80dd
> > > 
> > > This commit added both cpy and cprt, that makes your hypothesis not
> > > fit very well  
> > 
> > That commit adds it to three places:
> >  - MOV mode which is basically in mov_write_udta_tag() using '\251cpy'
> >    which published in Apple docs
> >  - 3GP mode using 'cprt' which is in ISO standard
> >  - mov_write_ilst_tag() is iTunes which is non-documented
> > 
> > The commit adds exactly one tag to each variant. To me my hyptothesis
> > still looks correct.
> 
> I was thinking and researching this more. It looks like:
>  - 3GP defines 'cprt' which is completely different encoding and
>    appears under different atom
>  - \251cpy is the QuickTime atom documented by Apple
>  - but it seems iTunes uses and has always used undocumented 'cprt'
>    which similar to other iTunes atoms
> 
> It seems that other software supporting iTunes support 'cprt' format.
> There are few other things that support also '\251cpy' variant in this
> context, but they are few.
> 
> Now I suspect ffmpeg started writing '\251cpy' atoms also for the
> iTunes tag based on the assumption that the tag there would follow
> QuickTime format as many other iTunes tags follow.
> 
> And this almost sounds like any other software supporting '\251cpy'
> here do it to support ffmpeg encoded incorrect streams.
> 
> My preference on fixing this is as follows:
> 1. Just change '\251cpy' to 'cprt' as this seems to be the canonical
>    atom
> 2. My previously suggested patch. Write 'cprt' by default, but have
>    flag to write the other tag
> 3. Write both by default, but add flag to suppress the '\251cpy' atom
> 
> Suggestions and additional input welcome.

if there is no reply from anyone providing more information than the
choice you prefer (1.) should be ok

thx


[...]
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