[FFmpeg-devel] Re: [DISCUSSION] Adding ARM64EC support to FFmpeg

["Rémi Denis-Courmont via ffmpeg-devel" <ffmpeg-devel@ffmpeg.org>]

Le perjantaina 3. lokakuuta 2025, 18.11.55 Itä-Euroopan kesäaika Martin 
Storsjö a écrit :
> Wanting to use the libav* libraries in a hybrid x86_64/arm64ec process
> seems like something quite plausible though. Not something I'd go out of
> my way to complicate other things to accomplish, but reasonable build
> system tweaks to allow such builds sound tolerable to me.

Is it that plausible? That seems far less plausible than running a plain 
x86_64 application on an Arm system. Especially for something performance 
sensitive as FFmpeg, you would want a proper native port. Sure, you could very 
well end up with slow x86 code due to "non-technical challenges" (euphemism 
for the vendor not providing an Arm build or your IT department lagging 
behind).

But realistically, you're not going to be able to replace an x86 
libavcodec.dll with an AArch64 libavcodec.dll in such an x86 app. The chance 
of finding the right build options to get a compatible ABI are pretty much 
zero. In fact, they are very exactly zero because the libavutil ABI depends on 
the ISA due notably to the CPU feature flags, configuration parameters, etc.

So this can only work if you have Arm64EC application code calling an 
hypothetical Arm64EC libav*, but also calling x86 code on independent code 
paths. Why would you not port the x86 code to Arm too (or run them in a 
separate process)? That seems pretty fringe if not academic to me.

-- 
Rémi Denis-Courmont
Hagalund ny stad, f.d. Finska republik Nylands



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