Re: [FFmpeg-devel] CI

["Martin Storsjö via ffmpeg-devel" <ffmpeg-devel@ffmpeg.org>]

On Fri, 22 Aug 2025, Timo Rothenpieler via ffmpeg-devel wrote:

> For arm I'm not sure if we really need qemu? All it might take is a 
> 32bit arm chroot on aarch64? Not sure if it works like x86 though, where 
> a 64bit CPU can also run 32bit code.

It works pretty much like x86, yes - you don't need QEMU, you can run it 
natively on an aarch64 kernel.

And you don't need a separate chroot - on Debian/Ubuntu multiarch it's 
quite straightforward to install 32 bit arm as a separate architecture:

     dpkg --add-architecture armhf
     apt-get update && apt-get install g++-arm-linux-gnueabihf libc6:armhf libstdc++6:armhf

This is enough for being able to build things for it, with 
--cross-prefix=arm-linux-gnueabihf- and to run the binaries normally.

That said, the very latest generations of aarch64 chips have removed 
support for executing in 32 bit mode; luckily the recent github aarch64 
runners (which are quite cutting edge otherwise, and have features like 
SVE2) still do support 32 bit. But e.g. on Amazon, the Graviton 4 series 
no longer supports 32 bit, and the Apple M1 (and newer ones) also lack 32 
bit support entirely.

// Martin

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