[FFmpeg-devel] [PATCH v2 1/2] avfilter/vf_blackdetect: add AVX2 SIMD version
Niklas Haas
ffmpeg at haasn.xyz
Thu Jul 17 13:45:24 EEST 2025
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
+
+#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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