ffmpeg requires NEON on armhf, which is not part of the ARMv7 ABI

[Edmund Grimley Evans <edmund.grimley.evans@gmail.com>]

As far as I know, the best way to implement run-time detection of
hardware capabilities is with getauxval(AT_HWCAP) and
getauxval(AT_HWCAP2).

There is some kind of NEON detection in ffmeg. See, for example:

https://sources.debian.net/src/ffmpeg/7:3.3.3-1/libavutil/arm/cpu.c/

That code appears to use /proc rather than getauxval. Is there a good
reason for that?

In case someone reading this has access to hardware (or a simulator)
without NEON but is not familiar with ffmpeg, what is a quick and easy
way of checking whether ffmpeg is working?

There are other libraries in Debian that do run-time detection of
NEON: fftw3 is one, I think.