[FFmpeg-devel] [PATCH v2 1/2] avfilter/vf_blackdetect: add AVX2 SIMD version
Zhao Zhili
quinkblack at foxmail.com
Fri Jul 18 14:35:49 EEST 2025
> On Jul 17, 2025, at 18:45, Niklas Haas <ffmpeg at haasn.xyz> wrote:
>
> From: Niklas Haas <git at haasn.dev>
>
> Requested by a user. Even with autovectorization enabled, the compiler
> performs a quite poor job of optimizing this function, due to not being
> able to take advantage of the pmaxub + pcmpeqb trick for counting the number
> of pixels less than or equal-to a threshold.
>
> blackdetect8_c: 4625.0 ( 1.00x)
> blackdetect8_avx2: 155.1 (29.83x)
> blackdetect16_c: 2529.4 ( 1.00x)
> blackdetect16_avx2: 163.6 (15.46x)
> ---
> libavfilter/vf_blackdetect.c | 33 +++---------
> libavfilter/vf_blackdetect.h | 71 ++++++++++++++++++++++++++
> libavfilter/x86/Makefile | 2 +
> libavfilter/x86/vf_blackdetect.asm | 73 +++++++++++++++++++++++++++
> libavfilter/x86/vf_blackdetect_init.c | 34 +++++++++++++
> 5 files changed, 188 insertions(+), 25 deletions(-)
> create mode 100644 libavfilter/vf_blackdetect.h
> create mode 100644 libavfilter/x86/vf_blackdetect.asm
> create mode 100644 libavfilter/x86/vf_blackdetect_init.c
>
> diff --git a/libavfilter/vf_blackdetect.c b/libavfilter/vf_blackdetect.c
> index 8be33a814d..b233bdfd60 100644
> --- a/libavfilter/vf_blackdetect.c
> +++ b/libavfilter/vf_blackdetect.c
> @@ -33,6 +33,7 @@
> #include "filters.h"
> #include "formats.h"
> #include "video.h"
> +#include "vf_blackdetect.h"
>
> typedef struct BlackDetectContext {
> const AVClass *class;
> @@ -53,6 +54,8 @@ typedef struct BlackDetectContext {
> int depth;
> int nb_threads;
> unsigned int *counter;
> +
> + ff_blackdetect_fn func;
> } BlackDetectContext;
>
> #define OFFSET(x) offsetof(BlackDetectContext, x)
> @@ -133,6 +136,7 @@ static int config_input(AVFilterLink *inlink)
> s->time_base = inlink->time_base;
> s->black_min_duration = s->black_min_duration_time / av_q2d(s->time_base);
> s->counter = av_calloc(s->nb_threads, sizeof(*s->counter));
> + s->func = ff_blackdetect_get_fn(depth);
> if (!s->counter)
> return AVERROR(ENOMEM);
>
> @@ -160,37 +164,16 @@ static int black_counter(AVFilterContext *ctx, void *arg,
> int jobnr, int nb_jobs)
> {
> BlackDetectContext *s = ctx->priv;
> - const unsigned int threshold = s->pixel_black_th_i;
> - unsigned int *counterp = &s->counter[jobnr];
> - AVFrame *in = arg;
> + const AVFrame *in = arg;
> const int plane = s->alpha ? 3 : 0;
> const int linesize = in->linesize[plane];
> - const int w = in->width;
> const int h = in->height;
> const int start = (h * jobnr) / nb_jobs;
> const int end = (h * (jobnr+1)) / nb_jobs;
> - const int size = end - start;
> - unsigned int counter = 0;
> -
> - if (s->depth == 8) {
> - const uint8_t *p = in->data[plane] + start * linesize;
> -
> - for (int i = 0; i < size; i++) {
> - for (int x = 0; x < w; x++)
> - counter += p[x] <= threshold;
> - p += linesize;
> - }
> - } else {
> - const uint16_t *p = (const uint16_t *)(in->data[plane] + start * linesize);
> -
> - for (int i = 0; i < size; i++) {
> - for (int x = 0; x < w; x++)
> - counter += p[x] <= threshold;
> - p += linesize / 2;
> - }
> - }
>
> - *counterp = counter;
> + s->counter[jobnr] = s->func(in->data[plane] + start * linesize,
> + linesize, in->width, end - start,
> + s->pixel_black_th_i);
>
> return 0;
> }
> diff --git a/libavfilter/vf_blackdetect.h b/libavfilter/vf_blackdetect.h
> new file mode 100644
> index 0000000000..361da2c5bc
> --- /dev/null
> +++ b/libavfilter/vf_blackdetect.h
> @@ -0,0 +1,71 @@
> +/*
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +#ifndef AVFILTER_VF_BLACKDETECT_H
> +#define AVFILTER_VF_BLACKDETECT_H
This break fate-source.
https://ffmpeg.org/pipermail/ffmpeg-devel/2025-July/346792.html
> +
> +#include <stddef.h>
> +#include <stdint.h>
> +
> +typedef unsigned (*ff_blackdetect_fn)(const uint8_t *src, ptrdiff_t stride,
> + ptrdiff_t width, ptrdiff_t height,
> + unsigned threshold);
> +
> +ff_blackdetect_fn ff_blackdetect_get_fn_x86(int depth);
> +
> +static unsigned count_pixels8_c(const uint8_t *src, ptrdiff_t stride,
> + ptrdiff_t width, ptrdiff_t height,
> + unsigned threshold)
> +{
> + unsigned int counter = 0;
> + while (height--) {
> + for (int x = 0; x < width; x++)
> + counter += src[x] <= threshold;
> + src += stride;
> + }
> + return counter;
> +}
> +
> +static unsigned count_pixels16_c(const uint8_t *src, ptrdiff_t stride,
> + ptrdiff_t width, ptrdiff_t height,
> + unsigned threshold)
> +{
> + unsigned int counter = 0;
> + while (height--) {
> + const uint16_t *src16 = (const uint16_t *) src;
> + for (int x = 0; x < width; x++)
> + counter += src16[x] <= threshold;
> + src += stride;
> + }
> + return counter;
> +}
> +
> +
> +static inline ff_blackdetect_fn ff_blackdetect_get_fn(int depth)
> +{
> + ff_blackdetect_fn fn = NULL;
> +#if ARCH_X86
> + fn = ff_blackdetect_get_fn_x86(depth);
> +#endif
> +
> + if (!fn)
> + fn = depth == 8 ? count_pixels8_c : count_pixels16_c;
> + return fn;
> +}
> +
> +#endif /* AVFILTER_VF_BLACKDETECT_H */
> diff --git a/libavfilter/x86/Makefile b/libavfilter/x86/Makefile
> index 0efe3f8d2c..86f7119a7b 100644
> --- a/libavfilter/x86/Makefile
> +++ b/libavfilter/x86/Makefile
> @@ -3,6 +3,7 @@ OBJS-$(CONFIG_SCENE_SAD) += x86/scene_sad_init.o
> OBJS-$(CONFIG_AFIR_FILTER) += x86/af_afir_init.o
> OBJS-$(CONFIG_ANLMDN_FILTER) += x86/af_anlmdn_init.o
> OBJS-$(CONFIG_ATADENOISE_FILTER) += x86/vf_atadenoise_init.o
> +OBJS-$(CONFIG_BLACKDETECT_FILTER) += x86/vf_blackdetect_init.o
> OBJS-$(CONFIG_BLEND_FILTER) += x86/vf_blend_init.o
> OBJS-$(CONFIG_BWDIF_FILTER) += x86/vf_bwdif_init.o
> OBJS-$(CONFIG_COLORSPACE_FILTER) += x86/colorspacedsp_init.o
> @@ -49,6 +50,7 @@ X86ASM-OBJS-$(CONFIG_SCENE_SAD) += x86/scene_sad.o
> X86ASM-OBJS-$(CONFIG_AFIR_FILTER) += x86/af_afir.o
> X86ASM-OBJS-$(CONFIG_ANLMDN_FILTER) += x86/af_anlmdn.o
> X86ASM-OBJS-$(CONFIG_ATADENOISE_FILTER) += x86/vf_atadenoise.o
> +X86ASM-OBJS-$(CONFIG_BLACKDETECT_FILTER) += x86/vf_blackdetect.o
> X86ASM-OBJS-$(CONFIG_BLEND_FILTER) += x86/vf_blend.o
> X86ASM-OBJS-$(CONFIG_BWDIF_FILTER) += x86/vf_bwdif.o
> X86ASM-OBJS-$(CONFIG_COLORSPACE_FILTER) += x86/colorspacedsp.o
> diff --git a/libavfilter/x86/vf_blackdetect.asm b/libavfilter/x86/vf_blackdetect.asm
> new file mode 100644
> index 0000000000..78c24c5adc
> --- /dev/null
> +++ b/libavfilter/x86/vf_blackdetect.asm
> @@ -0,0 +1,73 @@
> +;*****************************************************************************
> +;* x86-optimized functions for blackdetect filter
> +;*
> +;* Copyright (C) 2025 Niklas Haas
> +;*
> +;* This file is part of FFmpeg.
> +;*
> +;* FFmpeg is free software; you can redistribute it and/or
> +;* modify it under the terms of the GNU Lesser General Public
> +;* License as published by the Free Software Foundation; either
> +;* version 2.1 of the License, or (at your option) any later version.
> +;*
> +;* FFmpeg is distributed in the hope that it will be useful,
> +;* but WITHOUT ANY WARRANTY; without even the implied warranty of
> +;* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> +;* Lesser General Public License for more details.
> +;*
> +;* You should have received a copy of the GNU Lesser General Public
> +;* License along with FFmpeg; if not, write to the Free Software
> +;* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> +;*****************************************************************************
> +
> +%include "libavutil/x86/x86util.asm"
> +
> +SECTION .text
> +
> +%macro count_pixels_fn 1 ; depth
> +cglobal blackdetect_%1, 5, 7, 2, src, stride, width, height, threshold
> + movd xm1, thresholdd
> + %if %1 == 8
> + vpbroadcastb m1, xm1
> + %else
> + vpbroadcastw m1, xm1
> + shl widthq, 1
> + %endif
> + add srcq, widthq
> + neg widthq
> + xor r4, r4
> + mov r5, widthq
> + jmp .start
> +.loop:
> + popcnt r6d, r6d
> + add r4, r6
> +.start:
> + movu m0, [srcq + r5]
> + %if %1 == 8
> + pmaxub m0, m1
> + pcmpeqb m0, m1
> + %else
> + pmaxuw m0, m1
> + pcmpeqw m0, m1
> + %endif
> + pmovmskb r6d, m0
> + add r5, mmsize
> + jl .loop
> + ; handle tail by shifting away unused high elements
> + shlx r6d, r6d, r5d
> + popcnt r6d, r6d
> + add r4, r6
> + add srcq, strideq
> + mov r5, widthq
> + dec heightq
> + jg .start
> + %if %1 > 8
> + shr r4, 1
> + %endif
> + mov rax, r4
> + RET
> +%endmacro
> +
> +INIT_YMM avx2
> +count_pixels_fn 8
> +count_pixels_fn 16
> diff --git a/libavfilter/x86/vf_blackdetect_init.c b/libavfilter/x86/vf_blackdetect_init.c
> new file mode 100644
> index 0000000000..3780072589
> --- /dev/null
> +++ b/libavfilter/x86/vf_blackdetect_init.c
> @@ -0,0 +1,34 @@
> +/*
> + * Copyright (c) 2025 Niklas Haas
> + *
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with FFmpeg; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +#include "libavutil/attributes.h"
> +#include "libavutil/x86/cpu.h"
> +#include "libavfilter/vf_blackdetect.h"
> +
> +unsigned ff_blackdetect_8_avx2(const uint8_t *, ptrdiff_t, ptrdiff_t, ptrdiff_t, unsigned);
> +unsigned ff_blackdetect_16_avx2(const uint8_t *, ptrdiff_t, ptrdiff_t, ptrdiff_t, unsigned);
> +
> +av_cold ff_blackdetect_fn ff_blackdetect_get_fn_x86(int depth)
> +{
> + int cpu_flags = av_get_cpu_flags();
> + if (EXTERNAL_AVX2(cpu_flags))
> + return depth == 8 ? ff_blackdetect_8_avx2 : ff_blackdetect_16_avx2;
> + return NULL;
> +}
> --
> 2.50.1
>
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