lavfi/vf_blackdetect: R-V V count_pixels_8

SpacemiT X60:
blackdetect8_c:                                      14911.0 ( 1.00x)
blackdetect8_rvv_i32:                                  369.5 (40.35x)

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

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;
+}

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
+        addi    a3, a3, -1
+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
+        bnez    a3, 1b
+
+        mv      a0, a5
+        ret
+endfunc

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;
+    ff_blackdetect_fn fn;
-#if ARCH_X86 && HAVE_X86ASM
+
+#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)