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From: "Ronald S. Bultje" <rsbultje@gmail.com>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH] avcodec/x86/hevc: fix luma 12b overflow
Date: Sun, 25 Feb 2024 10:56:30 -0500
Message-ID: <CAEEMt2=B2TF550nA6QgSFd+Ng7oRizCGxyZ=ugrmo+FiKCoCUw@mail.gmail.com> (raw)
In-Reply-To: <20240225082755.355295-1-jdek@itanimul.li>

Hi,

On Sun, Feb 25, 2024 at 3:28 AM J. Dekker <jdek@itanimul.li> wrote:

> Weak filter can overflow in delta0 calculation before >> 4 in int16.
>
> Signed-off-by: J. Dekker <jdek@itanimul.li>
> ---
>
>  I do not know x86 simd at all, so this is just an attempt to fix
>  the implementation rather than write extremely performant code.
>
>  Suggestions welcome.
>

https://pastebin.com/KvcbQ2nK

Most of this can remain in 16bits when doing pabsw before the add. The odd
thing is that if I break (intentionally) the sse2 version, the ssse3/avx
checkams tests start failing occasionally also. I'm not sure why that is
the case. Not sure how to measure perf impact, I don't think there is any
for the non-12bit case (same number of instructions) but I didn't test very
hard and the perf is not very stable...

Ronald
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  reply	other threads:[~2024-02-25 15:56 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-02-25  8:27 J. Dekker
2024-02-25 15:56 ` Ronald S. Bultje [this message]
2024-02-25 16:22   ` Ronald S. Bultje
2024-02-25 16:24     ` Ronald S. Bultje
2024-02-25 16:28     ` James Almer
2024-02-25 16:41       ` Ronald S. Bultje
2024-02-25 22:30         ` Henrik Gramner via ffmpeg-devel
2024-02-25 23:00           ` Ronald S. Bultje
2024-02-26 14:26             ` J. Dekker

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