On Thu, 28 Jan 2021, Tomas Härdin wrote:
ons 2021-01-27 klockan 23:50 +0100 skrev Marton Balint:
On Wed, 27 Jan 2021, Tomas Härdin wrote:
> 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.
Thanks, I like this version much more. One comment is that I'd put an
assert right into mxf_lookup_local_tag instead of returning NULL if a tag
is not found, this way you can remove NULL-check asserts from individual
places where mxf_lookup_local_tag is called. Otherwise seems all fine.
There's not really anything to av_assert0() on in
mxf_lookup_local_tag(). Either way, I'm thinking replacing the return
NULL with either
av_log(NULL, AV_LOG_PANIC, "Tried to use unregistered local tag
0x%04x\n", tag);
abort();
or
av_assert0(0 && "Tried to use unregistered local tag");
or maybe
av_log(NULL, AV_LOG_PANIC, "Tried to use unregistered local tag
0x%04x\n", tag);
av_assert0(0);
to avoid explicitly calling abort()
I think we usually do av_assert0(0) in this case. I am not sure if the
error message is particularly useful, afterall who sees it should be a
programmer and file/line is printed by assert anyway, so a comment in the
source code before the assert makes more sense to me.
Regards,
Marton
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