Hello,
In order to update Exiv2, we need to know if this is okay to enable BMFF support. Patents
have theoretically expired and it is enabled by default in the latest version.
https://bugzilla.redhat.com/show_bug.cgi?id=1979565
https://github.com/Exiv2/exiv2/issues/1679
Upstream seems to think it is okay because it is over 20 years old. Also other packages in
Fedora are already using it, av1, jpeg-xl, any mp4 decoding.
By Jon Sneyers, one of the author of JPEG-XL:
I think this caution is erring on the side of paranoia, and possibly based on a
misunderstanding.
ISOBMFF is pretty old, old enough for it to be impossible to still have applicable
patents (patents expire after 20 years). It is a simple box-based container format that is
used by many formats, including MP4, JPEG 2000, and JPEG XL.
One particular use of ISOBMFF is HEIF, which is more recent, and for which there
actually are known patent claims by Nokia. HEIF does use the generic ISOBMFF box structure
and extends it by defining mechanisms to do cropping, layering, grids, rotation etc, which
are described in the HEIF spec. HEIF can be used with various payloads: when used with HEVC
it is called HEIC, when used with AV1 it is called AVIF.
While most people would consider patents on a container format ridiculous, it is a fact
that, at least in theory, if you use HEIF, you might risk patent litigation. Note that it
would not be the application implementor who could be sued, but the end-user who uses the
implementation and thereby possibly needs a patent license from Nokia.
This is only true specifically for HEIF though, not for ISOBMFF in general. Parsing the
MP4 or JPEG 2000 container (which do not use HEIF) carries absolutely no risk in terms of
patents, since they only use ISOBMFF, not HEIF. The same is true for JPEG XL, which has
explicitly avoided using the HEIF container exactly for this reason.
TL;DR: ISOBMFF is OK, HEIF might be risky.
So just to be clear: reading BMFF is not an issue, it is over 20 years old so even if
it was an issue in the past (it wasn't) it now certainly isn't anymore.
Reading HEIF-specific boxes is something else, but as long as Exiv2 is not doing that,
there obviously is no issue either. Note that other FOSS tools like libheif and libavif
actually do read those boxes, and they do seem to get away with it (but I can understand why
you wouldn't want to do that; those boxes are from 2015 and Nokia does claim patents on them
so it will only really be 'safe' to use that functionality in 2035).
So while I appreciate the caution, I think it's OK to just enable the BMFF code by
default (perhaps have an option to disable it, if someone is still for some reason worried,
but imo that would be an unfounded worry). Otherwise most of the modern image codecs (jp2,
jxl, avif and heic) end up being unsupported by default, for no good reason, which seems a
suboptimal situation.
Could we come to a resolution of that situation quickly?
Thank you,
Have a great sunday.
Robert-André
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