[FFmpeg-devel] [PATCH] avformat/mxf: Establish register of local tags

[Tomas Härdin]

ons 2021-01-27 klockan 22:24 +0100 skrev Tomas Härdin:
> ons 2021-01-27 klockan 21:38 +0100 skrev Marton Balint:
> > On Wed, 27 Jan 2021, Tomas Härdin wrote:
> > 
> > > Hi
> > > 
> > > Ticket #9079 brought this about. This should prevent accidentally
> > > adding local tags that are not registered in the primer. It also allows
> > > us to omit tags that we know won't be used, in a manner that is more
> > > elegant than the old code.
> > > 
> > > The actual meat of this patch is mxf_mark_tag_unused(),
> > > mxf_write_primer_pack(), mxf_write_local_tag() and
> > > ff_mxf_lookup_local_tag()
> > 
> > IMHO you should not move the local tags to mxf.c, because only encoding 
> > uses them.
> > 
> > The only exception where sharing made sense is 
> > ff_mxf_mastering_display_local_tags, but that is super ugly that you 
> > now lookup them in mxfdec.c based on local tags we assign them for 
> > encoding. Not to mention the linear search you use for each lookup...
> 
> We could sort them and use a binary search, but I wanted some feedback
> on this idea before going further. There's not terribly many of them
> 
> I'd like to avoid having the full ULs twice in the code. The only way I
> can see how to do that is with #defines
> 
> > So I suggest you simply duplicate the 4 UL-s to the single local tags 
> > array you make and keep them in mxfenc.c, that way you also don't have to 
> > specify the array size manually...
> 
> That might conflict with Andreas' deduplication efforts. But yeah, the
> thought did occur to me

Here's an updated patch. Feedback welcome.

/Tomas
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