Comment # 7 on bug 4361 from Dominik 'Rathann' Mierzejewski

(In reply to Simone Caronni from comment #6)
> (In reply to Dominik 'Rathann' Mierzejewski from comment #3)
> > - libva is required to build with QSV.
> 
> Are you sure for this? FFMpeg in RPMFusion is already built with mfx/QSV.

It seems to be referenced here unconditionally if QSV is enabled:

test/module.defs:
ifeq (1,$(FEATURE.qsv))
    TEST.GCC.D += USE_QSV HAVE_THREADS=1
ifeq ($(BUILD.system),linux)
    TEST.GCC.l += va va-drm
endif
endif

I don't see any option to disable it via configure command line and since it
doesn't hurt anything apart from a small additional build dependency, I put it
in. If you want, feel free to patch it out.

> > - Drop support for building with libav.
> 
> I will make a new test this evening, but my attempts to build with FFMpeg
> months ago showed that it was breaking all UTF-8 subtitles detection (they
> are simply not detected anymore), so it means most of the Asian titles
> (Anime, etc.) and most of the BluRays will not have any subtitle. Can you
> still leave the optional part in, just disabled by default?

Sure.