[FFmpeg-devel] Re: [GASPP PATCH 1/2] Pass "-machine" options through to armasm

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

Hi,

Thanks for getting back to us. See below.

Le 20 janvier 2026 09:26:56 GMT+02:00, Harish Raja Selvan via ffmpeg-devel <ffmpeg-devel@ffmpeg.org> a écrit :
>Hi Martin and Rémi,
>I wanted to add a bit more context on the practical use case.
>There are several large and widely used Windows applications especially in enterprise and creator workflows that remain x64-only and rely heavily on FFmpeg at runtime. Examples include Feishu (Lark),
> Jianying / CapCut, and DingTalk, which are used at very large scale.
>Fully porting these applications to native ARM64 is a significant engineering effort and is taking considerable time.

Lark is already running on iOS and Android, so I doubt that it'd be x86-only. ByteDance is a 6-digit staff company, surely it can spare a couple of engineers to make a port for Windows on Arm64.

On the other hand, there still is no credible plan how we would make a proper Arm64EC port of FFmpeg. Recall that the current patch only fixes the C code, but it left broken:
- the assembler code, which doesn't conform to the Arm64EC ABI,
- the binary interface, which assumes an Arm64 caller rather than x86 (breaking at least CPU flags).

Overall I doubt that it would be easier to port FFmpeg to Arm64EC *properly* than to port Feishu to Arm64...

Ditto CapCut by the same company and which also has an Harmony OS port that would require Arm support too.

And pretty much the same with DingTalk, albeit by another large Chinese tech company.

> On Windows ARM devices, FFmpeg becomes a major performance bottleneck under x64 emulation.

We all get that, but the elephant in the room that you have not addressed once in the past months is how to make FFmpeg actually support Arm64EC. Currently it compiles, but that's just the easy 10% of the complete job.

Do you have a plan to address the outstanding shortcomings? What would the actual performance look like in such case, seen as it would disable most or all of the assembler optimisations?

Otherwise we are talking in pure hypotheticals here.

>If there are any maintenance concerns, technical challenges, or areas where our help would be useful, we would be glad to support and contribute. Having ARM64EC builds of FFmpeg is important for enabling these real-world use cases.

See above.

Br,
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