[FFmpeg-devel] [PATCH] lavfi/vf_blackdetect: R-V V optimisations (PR #21209)

[FFmpeg-devel] [PATCH] lavfi/vf_blackdetect: R-V V optimisations (PR #21209)

[Rémi Denis-Courmont via ffmpeg-devel]

PR #21209 opened by Rémi Denis-Courmont (Courmisch)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21209
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21209.patch


From 637bcb101a9dd6812d501f8025c54e3d97701eaa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9mi=20Denis-Courmont?= <remi@remlab.net>
Date: Mon, 15 Dec 2025 20:37:54 +0200
Subject: [PATCH 1/2] lavfi/vf_blackdetect: add R-V V count_pixels_8

SpacemiT X60:
blackdetect8_c:                                      14911.0 ( 1.00x)
blackdetect8_rvv_i32:                                  369.5 (40.35x)
---
 libavfilter/riscv/Makefile              |  2 ++
 libavfilter/riscv/vf_blackdetect_init.c | 42 +++++++++++++++++++++++
 libavfilter/riscv/vf_blackdetect_rvv.S  | 45 +++++++++++++++++++++++++
 libavfilter/vf_blackdetect.h            | 10 ++++--
 4 files changed, 97 insertions(+), 2 deletions(-)
 create mode 100644 libavfilter/riscv/vf_blackdetect_init.c
 create mode 100644 libavfilter/riscv/vf_blackdetect_rvv.S

diff --git a/libavfilter/riscv/Makefile b/libavfilter/riscv/Makefile
index 14a4470d96..32b07eec1a 100644
--- a/libavfilter/riscv/Makefile
+++ b/libavfilter/riscv/Makefile
@@ -1,4 +1,6 @@
 OBJS-$(CONFIG_AFIR_FILTER)                   += riscv/af_afir_init.o
 RVV-OBJS-$(CONFIG_AFIR_FILTER)               += riscv/af_afir_rvv.o
+OBJS-$(CONFIG_BLACKDETECT_FILTER) += riscv/vf_blackdetect_init.o
+RVV-OBJS-$(CONFIG_BLACKDETECT_FILTER) += riscv/vf_blackdetect_rvv.o
 
 SHLIBOBJS += riscv/cpu_common.o
diff --git a/libavfilter/riscv/vf_blackdetect_init.c b/libavfilter/riscv/vf_blackdetect_init.c
new file mode 100644
index 0000000000..665603c114
--- /dev/null
+++ b/libavfilter/riscv/vf_blackdetect_init.c
@@ -0,0 +1,42 @@
+/*
+ * Copyright © 2025 Rémi Denis-Courmont.
+ *
+ * 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 "config.h"
+
+#include "libavutil/attributes.h"
+#include "libavutil/cpu.h"
+#include "libavfilter/vf_blackdetect.h"
+
+unsigned ff_count_pixels_8_rvv(const uint8_t *src, ptrdiff_t stride,
+                               ptrdiff_t width, ptrdiff_t height,
+                               unsigned threshold);
+
+ff_blackdetect_fn ff_blackdetect_get_fn_riscv(int depth)
+{
+#if HAVE_RVV
+    int flags = av_get_cpu_flags();
+
+    if (flags & AV_CPU_FLAG_RVV_I32) {
+        if (depth <= 8)
+            return ff_count_pixels_8_rvv;
+    }
+#endif
+    return NULL;
+}
diff --git a/libavfilter/riscv/vf_blackdetect_rvv.S b/libavfilter/riscv/vf_blackdetect_rvv.S
new file mode 100644
index 0000000000..fd96cff6e7
--- /dev/null
+++ b/libavfilter/riscv/vf_blackdetect_rvv.S
@@ -0,0 +1,45 @@
+/*
+ * Copyright © 2025 Rémi Denis-Courmont.
+ *
+ * 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/riscv/asm.S"
+
+func ff_count_pixels_8_rvv, zve32x
+        lpad    0
+        mv      a5, zero
+        sub     a1, a1, a2
+1:
+        mv      t2, a2
+2:
+        vsetvli t1, t2, e8, m8, ta, ma
+        vle8.v  v8, (a0)
+        sub     t2, t2, t1
+        vmsleu.vx   v0, v8, a4
+        add     a0, t1, a0
+        vcpop.m t3, v0
+        add     a5, t3, a5
+        bnez    t2, 2b
+
+        add     a0, a0, a1
+        addi    a3, a3, -1
+        bnez    a3, 1b
+
+        mv      a0, a5
+        ret
+endfunc
diff --git a/libavfilter/vf_blackdetect.h b/libavfilter/vf_blackdetect.h
index e51beda3a4..e5b3aa8833 100644
--- a/libavfilter/vf_blackdetect.h
+++ b/libavfilter/vf_blackdetect.h
@@ -28,6 +28,7 @@ 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_riscv(int depth);
 ff_blackdetect_fn ff_blackdetect_get_fn_x86(int depth);
 
 static unsigned count_pixels8_c(const uint8_t *src, ptrdiff_t stride,
@@ -60,9 +61,14 @@ static unsigned count_pixels16_c(const uint8_t *src, ptrdiff_t stride,
 
 static inline ff_blackdetect_fn ff_blackdetect_get_fn(int depth)
 {
-    ff_blackdetect_fn fn = NULL;
-#if ARCH_X86 && HAVE_X86ASM
+    ff_blackdetect_fn fn;
+
+#if ARCH_RISCV
+    fn = ff_blackdetect_get_fn_riscv(depth);
+#elif ARCH_X86 && HAVE_X86ASM
     fn = ff_blackdetect_get_fn_x86(depth);
+#else
+    fn = NULL;
 #endif
 
     if (!fn)
-- 
2.49.1


From b31c4c08ff7c50d137ffac0432b893fa2e943e9a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9mi=20Denis-Courmont?= <remi@remlab.net>
Date: Mon, 15 Dec 2025 20:40:24 +0200
Subject: [PATCH 2/2] lavfi/vf_blackdetect: R-V V count_pixels_16

SpacemiT X60:
blackdetect16_c:                                      7171.0 ( 1.00x)
blackdetect16_rvv_i32:                                 383.6 (18.69x)
---
 libavfilter/riscv/vf_blackdetect_init.c |  5 +++++
 libavfilter/riscv/vf_blackdetect_rvv.S  | 25 +++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/libavfilter/riscv/vf_blackdetect_init.c b/libavfilter/riscv/vf_blackdetect_init.c
index 665603c114..fcf63501e5 100644
--- a/libavfilter/riscv/vf_blackdetect_init.c
+++ b/libavfilter/riscv/vf_blackdetect_init.c
@@ -27,6 +27,9 @@
 unsigned ff_count_pixels_8_rvv(const uint8_t *src, ptrdiff_t stride,
                                ptrdiff_t width, ptrdiff_t height,
                                unsigned threshold);
+unsigned ff_count_pixels_16_rvv(const uint8_t *src, ptrdiff_t stride,
+                                ptrdiff_t width, ptrdiff_t height,
+                                unsigned threshold);
 
 ff_blackdetect_fn ff_blackdetect_get_fn_riscv(int depth)
 {
@@ -36,6 +39,8 @@ ff_blackdetect_fn ff_blackdetect_get_fn_riscv(int depth)
     if (flags & AV_CPU_FLAG_RVV_I32) {
         if (depth <= 8)
             return ff_count_pixels_8_rvv;
+        if ((flags & AV_CPU_FLAG_RVB) && (depth <= 16))
+            return ff_count_pixels_16_rvv;
     }
 #endif
     return NULL;
diff --git a/libavfilter/riscv/vf_blackdetect_rvv.S b/libavfilter/riscv/vf_blackdetect_rvv.S
index fd96cff6e7..b294a89a61 100644
--- a/libavfilter/riscv/vf_blackdetect_rvv.S
+++ b/libavfilter/riscv/vf_blackdetect_rvv.S
@@ -43,3 +43,28 @@ func ff_count_pixels_8_rvv, zve32x
         mv      a0, a5
         ret
 endfunc
+
+func ff_count_pixels_16_rvv, zve32x, zba
+        lpad    0
+        slli    t2, a2, 1
+        mv      a5, zero
+        sub     a1, a1, t2
+1:
+        mv      t2, a2
+2:
+        vsetvli t1, t2, e16, m8, ta, ma
+        vle16.v v8, (a0)
+        sub     t2, t2, t1
+        vmsleu.vx   v0, v8, a4
+        sh1add  a0, t1, a0
+        vcpop.m t3, v0
+        add     a5, t3, a5
+        bnez    t2, 2b
+
+        add     a0, a0, a1
+        addi    a3, a3, -1
+        bnez    a3, 1b
+
+        mv      a0, a5
+        ret
+endfunc
-- 
2.49.1

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