Re: [FFmpeg-devel] [PATCH v4 13/13] avfilter/x86/f_ebur128: implement AVX true peak calculation

[Niklas Haas <ffmpeg@haasn.xyz>]

On Tue, 17 Jun 2025 14:06:06 +0200 Niklas Haas <ffmpeg@haasn.xyz> wrote:
> From: Niklas Haas <git@haasn.dev>
>
> Stereo only, for simplicity. Slightly faster than the C code.

I will drop this and the prior commit and resubmit them in a refactored form
that also speeds up the sample peak calculation.

In the meantime, I would appreciate a review of the rest.

> ---
>  libavfilter/f_ebur128.c          |  8 +++-----
>  libavfilter/f_ebur128.h          |  2 +-
>  libavfilter/x86/f_ebur128.asm    | 25 +++++++++++++++++++++++++
>  libavfilter/x86/f_ebur128_init.c |  9 +++++++--
>  4 files changed, 36 insertions(+), 8 deletions(-)
>
> diff --git a/libavfilter/f_ebur128.c b/libavfilter/f_ebur128.c
> index 0adc89c823..c64f6ed032 100644
> --- a/libavfilter/f_ebur128.c
> +++ b/libavfilter/f_ebur128.c
> @@ -502,6 +502,9 @@ static int config_audio_output(AVFilterLink *outlink)
>              return AVERROR(ENOMEM);
>      }
>
> +#if ARCH_X86
> +    ff_ebur128_init_x86(&ebur128->dsp, nb_channels);
> +#endif
>      return 0;
>  }
>
> @@ -581,11 +584,6 @@ static av_cold int init(AVFilterContext *ctx)
>
>      ebur128->dsp.filter_channels = ff_ebur128_filter_channels_c;
>      ebur128->dsp.true_peak = ff_ebur128_true_peak_c;
> -
> -#if ARCH_X86
> -    ff_ebur128_init_x86(&ebur128->dsp);
> -#endif
> -
>      return 0;
>  }
>
> diff --git a/libavfilter/f_ebur128.h b/libavfilter/f_ebur128.h
> index 8aab7838a0..5fb9d4a8d5 100644
> --- a/libavfilter/f_ebur128.h
> +++ b/libavfilter/f_ebur128.h
> @@ -53,7 +53,7 @@ static_assert(offsetof(EBUR128DSPContext, pre) == 0,                   "struct l
>  static_assert(offsetof(EBUR128DSPContext, rlb) == 5  * sizeof(double), "struct layout mismatch");
>  static_assert(offsetof(EBUR128DSPContext, y)   == 10 * sizeof(double), "struct layout mismatch");
>
> -void ff_ebur128_init_x86(EBUR128DSPContext *dsp);
> +void ff_ebur128_init_x86(EBUR128DSPContext *dsp, int nb_channels);
>
>  void ff_ebur128_filter_channels_c(const EBUR128DSPContext *, const double *,
>                                    double *, double *, double *, double *, int);
> diff --git a/libavfilter/x86/f_ebur128.asm b/libavfilter/x86/f_ebur128.asm
> index d9cc8d9361..53dd3f858d 100644
> --- a/libavfilter/x86/f_ebur128.asm
> +++ b/libavfilter/x86/f_ebur128.asm
> @@ -39,6 +39,10 @@ struc DSP
>      .z resq 1
>  endstruc
>
> +SECTION_RODATA
> +
> +abs_mask: dq 0x7FFFFFFFFFFFFFFF
> +
>  SECTION .text
>
>  %macro MOVNQ 3 ; num, dst, src
> @@ -139,3 +143,24 @@ cglobal ebur128_filter_channels, 7, 9, 14, dsp, samples, cache400, cache3000, su
>      test channelsd, channelsd
>      jnz .loop
>      RET
> +
> +cglobal ebur128_true_peak_stereo, 5, 6, 4, tp, tppf, channels, samples, nb_samples
> +    vpbroadcastq m4, [abs_mask]
> +    pxor m0, m0      ; maxpeak
> +    movupd m1, [tpq] ; tp
> +    pxor m2, m2      ; tppf
> +.inner:
> +    movupd m3, [samplesq]
> +    add samplesq, 16
> +    pand m3, m4
> +    maxpd m1, m3
> +    maxpd m2, m3
> +    dec nb_samplesd
> +    jg .inner
> +    movupd [tpq],  m1
> +    movupd [tppfq], m2
> +    maxpd m0, m1
> +    shufpd m1, m0, m0, 1
> +    maxpd m0, m1
> +    movq rax, m0
> +    RET
> diff --git a/libavfilter/x86/f_ebur128_init.c b/libavfilter/x86/f_ebur128_init.c
> index 8f38aee967..527e5e4dbc 100644
> --- a/libavfilter/x86/f_ebur128_init.c
> +++ b/libavfilter/x86/f_ebur128_init.c
> @@ -26,10 +26,15 @@
>  void ff_ebur128_filter_channels_avx(const EBUR128DSPContext *, const double *,
>                                      double *, double *, double *, double *, int);
>
> -av_cold void ff_ebur128_init_x86(EBUR128DSPContext *dsp)
> +double ff_ebur128_true_peak_stereo_avx(double *, double *, int, const double *, int);
> +
> +av_cold void ff_ebur128_init_x86(EBUR128DSPContext *dsp, int nb_channels)
>  {
>      int cpu_flags = av_get_cpu_flags();
>
> -    if (ARCH_X86_64 && EXTERNAL_AVX(cpu_flags))
> +    if (ARCH_X86_64 && EXTERNAL_AVX(cpu_flags)) {
>          dsp->filter_channels = ff_ebur128_filter_channels_avx;
> +        if (nb_channels == 2)
> +            dsp->true_peak = ff_ebur128_true_peak_stereo_avx;
> +    }
>  }
> --
> 2.49.0
>
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