* [FFmpeg-devel] [PATCH] vf_blend (PR #20634)
@ 2025-10-01 7:01 mkver via ffmpeg-devel
0 siblings, 0 replies; only message in thread
From: mkver via ffmpeg-devel @ 2025-10-01 7:01 UTC (permalink / raw)
To: ffmpeg-devel; +Cc: mkver
PR #20634 opened by mkver
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20634
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20634.patch
>From f2717889b4bff014ad8d00a98dc94761ed56c325 Mon Sep 17 00:00:00 2001
From: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Date: Wed, 1 Oct 2025 07:56:49 +0200
Subject: [PATCH 1/2] avfilter/blend_modes: Use stride in bytes
The blend functions currently convert strides from bytes to elements
of the type by using the stride /= sizeof(pixel) idiom. Yet this has
several drawbacks:
1. It invokes undefined behavior that happens to work when stride is
negative: size_t is typically the unsigned type of ptrdiff_t and
therefore the division will be performed as size_t, i.e. use logical
right shifts, making stride very big when sizeof(pixel) is > 1. This
works, because pointer to pixel for accesses entails an implicit
factor of sizeof(pixel) so that everything is correct modulo SIZE_MAX.
Yet this is UB and UBSan complains about it.
2. It makes the compiler emit actual shifts/ands to discard the low bits
shifted away.
3. There may be systems where alignof(uint16_t) or alignof(float) is
strictly smaller than their sizeof, so that the stride (in bytes) is
not guaranteed to be multiple of these sizeofs. In this case, dividing
by sizeof(pixel) is simply wrong.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
---
libavfilter/blend_modes.c | 16 ++++++----------
libavfilter/vf_blend_init.h | 16 ++++++----------
2 files changed, 12 insertions(+), 20 deletions(-)
diff --git a/libavfilter/blend_modes.c b/libavfilter/blend_modes.c
index 9b1e78b146..35e365996c 100644
--- a/libavfilter/blend_modes.c
+++ b/libavfilter/blend_modes.c
@@ -92,22 +92,18 @@ static void fn0(NAME)(const uint8_t *_top, ptrdiff_t top_linesize, \
ptrdiff_t width, ptrdiff_t height, \
FilterParams *param, SliceParams *sliceparam) \
{ \
- const PIXEL *top = (const PIXEL *)_top; \
- const PIXEL *bottom = (const PIXEL *)_bottom; \
- PIXEL *dst = (PIXEL *)_dst; \
const float opacity = param->opacity; \
\
- dst_linesize /= sizeof(PIXEL); \
- top_linesize /= sizeof(PIXEL); \
- bottom_linesize /= sizeof(PIXEL); \
- \
for (int i = 0; i < height; i++) { \
+ const PIXEL *top = (const PIXEL *)_top; \
+ const PIXEL *bottom = (const PIXEL *)_bottom; \
+ PIXEL *dst = (PIXEL *)_dst; \
for (int j = 0; j < width; j++) { \
dst[j] = top[j] + ((EXPR)-top[j]) * opacity; \
} \
- dst += dst_linesize; \
- top += top_linesize; \
- bottom += bottom_linesize; \
+ _dst += dst_linesize; \
+ _top += top_linesize; \
+ _bottom += bottom_linesize; \
} \
}
diff --git a/libavfilter/vf_blend_init.h b/libavfilter/vf_blend_init.h
index 98d440fe67..7f66796e3e 100644
--- a/libavfilter/vf_blend_init.h
+++ b/libavfilter/vf_blend_init.h
@@ -82,22 +82,18 @@ static void blend_normal_##name(const uint8_t *_top, ptrdiff_t top_linesize,
ptrdiff_t width, ptrdiff_t height, \
FilterParams *param, SliceParams *sliceparam) \
{ \
- const type *top = (const type*)_top; \
- const type *bottom = (const type*)_bottom; \
- type *dst = (type*)_dst; \
const float opacity = param->opacity; \
\
- dst_linesize /= sizeof(type); \
- top_linesize /= sizeof(type); \
- bottom_linesize /= sizeof(type); \
- \
for (int i = 0; i < height; i++) { \
+ const type *top = (const type*)_top; \
+ const type *bottom = (const type*)_bottom; \
+ type *dst = (type*)_dst; \
for (int j = 0; j < width; j++) { \
dst[j] = top[j] * opacity + bottom[j] * (1.f - opacity); \
} \
- dst += dst_linesize; \
- top += top_linesize; \
- bottom += bottom_linesize; \
+ _dst += dst_linesize; \
+ _top += top_linesize; \
+ _bottom += bottom_linesize; \
} \
}
--
2.49.1
>From 5c4166f5a2def849a19d698d463af5f8a403f822 Mon Sep 17 00:00:00 2001
From: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Date: Wed, 1 Oct 2025 08:27:14 +0200
Subject: [PATCH 2/2] avfilter/blend_modes: Don't build duplicate functions
Some of the blend mode functions only depend on the underlying type
and therefore need only one version for 9, 10, 12, 14, 16 bits.
This saved 35104B with GCC and 26880B with Clang.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
---
libavfilter/blend_modes.c | 29 +++++++++++++++++++----------
libavfilter/vf_blend_init.h | 20 ++++++++++----------
2 files changed, 29 insertions(+), 20 deletions(-)
diff --git a/libavfilter/blend_modes.c b/libavfilter/blend_modes.c
index 35e365996c..fff9864a04 100644
--- a/libavfilter/blend_modes.c
+++ b/libavfilter/blend_modes.c
@@ -34,16 +34,21 @@
#define MAX 255
#define HALF 128
#define CLIP(x) (av_clip_uint8(x))
+#define BUILD_TYPE_SPECIFIC_FUNCS
#elif DEPTH == 32
#define PIXEL float
#define MAX 1.f
#define HALF 0.5f
#define CLIP(x) (x)
+#define BUILD_TYPE_SPECIFIC_FUNCS
#else
#define PIXEL uint16_t
#define MAX ((1 << DEPTH) - 1)
#define HALF (1 << (DEPTH - 1))
#define CLIP(x) ((int)av_clip_uintp2(x, DEPTH))
+#if DEPTH == 16
+#define BUILD_TYPE_SPECIFIC_FUNCS
+#endif
#endif
#undef MULTIPLY
@@ -109,13 +114,10 @@ static void fn0(NAME)(const uint8_t *_top, ptrdiff_t top_linesize, \
fn(addition, FFMIN(MAX, A + B))
fn(grainmerge, CLIP(A + B - HALF))
-fn(average, (A + B) / 2)
-fn(subtract, FFMAX(0, A - B))
fn(multiply, MULTIPLY(1, A, B))
fn(multiply128,CLIP((A - HALF) * B / MDIV + HALF))
fn(negation, MAX - FFABS(MAX - A - B))
fn(extremity, FFABS(MAX - A - B))
-fn(difference, FFABS(A - B))
fn(grainextract, CLIP(HALF + A - B))
fn(screen, SCREEN(1, A, B))
fn(overlay, (A < HALF) ? MULTIPLY(2, A, B) : SCREEN(2, A, B))
@@ -123,8 +125,6 @@ fn(hardlight, (B < HALF) ? MULTIPLY(2, B, A) : SCREEN(2, B, A))
fn(hardmix, (A < (MAX - B)) ? 0: MAX)
fn(heat, (A == 0) ? 0 : MAX - FFMIN(((MAX - B) * (MAX - B)) / A, MAX))
fn(freeze, (B == 0) ? 0 : MAX - FFMIN(((MAX - A) * (MAX - A)) / B, MAX))
-fn(darken, FFMIN(A, B))
-fn(lighten, FFMAX(A, B))
fn(divide, CLIP(B == 0 ? MAX : MAX * A / B))
fn(dodge, DODGE(A, B))
fn(burn, BURN(A, B))
@@ -134,15 +134,24 @@ fn(pinlight, (B < HALF) ? FFMIN(A, 2 * B) : FFMAX(A, 2 * (B - HALF)))
fn(phoenix, FFMIN(A, B) - FFMAX(A, B) + MAX)
fn(reflect, (B == MAX) ? B : FFMIN(MAX, (A * A / (MAX - B))))
fn(glow, (A == MAX) ? A : FFMIN(MAX, (B * B / (MAX - A))))
-fn(and, INT2FLOAT(FLOAT2INT(A) & FLOAT2INT(B)))
-fn(or, INT2FLOAT(FLOAT2INT(A) | FLOAT2INT(B)))
-fn(xor, INT2FLOAT(FLOAT2INT(A) ^ FLOAT2INT(B)))
fn(vividlight, (A < HALF) ? BURN(2 * A, B) : DODGE(2 * (A - HALF), B))
fn(linearlight,CLIP((B < HALF) ? B + 2 * A - MAX : B + 2 * (A - HALF)))
fn(softdifference,CLIP((A > B) ? (B == MAX) ? 0 : (A - B) * MAX / (MAX - B) : (B == 0) ? 0 : (B - A) * MAX / B))
-fn(geometric, GEOMETRIC(A, B))
-fn(harmonic, A == 0 && B == 0 ? 0 : 2LL * A * B / (A + B))
fn(bleach, (MAX - B) + (MAX - A) - MAX)
fn(stain, 2 * MAX - A - B)
fn(interpolate,LRINTF(MAX * (2 - cosf(A * M_PI / MAX) - cosf(B * M_PI / MAX)) * 0.25f))
fn(hardoverlay,A == MAX ? MAX : FFMIN(MAX, MAX * B / (2 * MAX - 2 * A) * (A > HALF) + 2 * A * B / MAX * (A <= HALF)))
+
+#ifdef BUILD_TYPE_SPECIFIC_FUNCS
+fn(average, (A + B) / 2)
+fn(subtract, FFMAX(0, A - B))
+fn(difference, FFABS(A - B))
+fn(darken, FFMIN(A, B))
+fn(lighten, FFMAX(A, B))
+fn(and, INT2FLOAT(FLOAT2INT(A) & FLOAT2INT(B)))
+fn(or, INT2FLOAT(FLOAT2INT(A) | FLOAT2INT(B)))
+fn(xor, INT2FLOAT(FLOAT2INT(A) ^ FLOAT2INT(B)))
+fn(geometric, GEOMETRIC(A, B))
+fn(harmonic, A == 0 && B == 0 ? 0 : 2LL * A * B / (A + B))
+#undef BUILD_TYPE_SPECIFIC_FUNCS
+#endif
\ No newline at end of file
diff --git a/libavfilter/vf_blend_init.h b/libavfilter/vf_blend_init.h
index 7f66796e3e..297ca0514f 100644
--- a/libavfilter/vf_blend_init.h
+++ b/libavfilter/vf_blend_init.h
@@ -107,11 +107,11 @@ static av_cold void init_blend_func_##depth##_##nbits##bit(FilterParams *param)
switch (param->mode) { \
case BLEND_ADDITION: param->blend = blend_addition_##depth##bit; break; \
case BLEND_GRAINMERGE: param->blend = blend_grainmerge_##depth##bit; break; \
- case BLEND_AND: param->blend = blend_and_##depth##bit; break; \
- case BLEND_AVERAGE: param->blend = blend_average_##depth##bit; break; \
+ case BLEND_AND: param->blend = blend_and_##nbits##bit; break; \
+ case BLEND_AVERAGE: param->blend = blend_average_##nbits##bit; break; \
case BLEND_BURN: param->blend = blend_burn_##depth##bit; break; \
- case BLEND_DARKEN: param->blend = blend_darken_##depth##bit; break; \
- case BLEND_DIFFERENCE: param->blend = blend_difference_##depth##bit; break; \
+ case BLEND_DARKEN: param->blend = blend_darken_##nbits##bit; break; \
+ case BLEND_DIFFERENCE: param->blend = blend_difference_##nbits##bit; break; \
case BLEND_GRAINEXTRACT: param->blend = blend_grainextract_##depth##bit; break; \
case BLEND_DIVIDE: param->blend = blend_divide_##depth##bit; break; \
case BLEND_DODGE: param->blend = blend_dodge_##depth##bit; break; \
@@ -122,25 +122,25 @@ static av_cold void init_blend_func_##depth##_##nbits##bit(FilterParams *param)
case BLEND_HARDLIGHT: param->blend = blend_hardlight_##depth##bit; break; \
case BLEND_HARDMIX: param->blend = blend_hardmix_##depth##bit; break; \
case BLEND_HEAT: param->blend = blend_heat_##depth##bit; break; \
- case BLEND_LIGHTEN: param->blend = blend_lighten_##depth##bit; break; \
+ case BLEND_LIGHTEN: param->blend = blend_lighten_##nbits##bit; break; \
case BLEND_LINEARLIGHT: param->blend = blend_linearlight_##depth##bit; break; \
case BLEND_MULTIPLY: param->blend = blend_multiply_##depth##bit; break; \
case BLEND_MULTIPLY128: param->blend = blend_multiply128_##depth##bit; break; \
case BLEND_NEGATION: param->blend = blend_negation_##depth##bit; break; \
case BLEND_NORMAL: param->blend = blend_normal_##nbits##bit; break; \
- case BLEND_OR: param->blend = blend_or_##depth##bit; break; \
+ case BLEND_OR: param->blend = blend_or_##nbits##bit; break; \
case BLEND_OVERLAY: param->blend = blend_overlay_##depth##bit; break; \
case BLEND_PHOENIX: param->blend = blend_phoenix_##depth##bit; break; \
case BLEND_PINLIGHT: param->blend = blend_pinlight_##depth##bit; break; \
case BLEND_REFLECT: param->blend = blend_reflect_##depth##bit; break; \
case BLEND_SCREEN: param->blend = blend_screen_##depth##bit; break; \
case BLEND_SOFTLIGHT: param->blend = blend_softlight_##depth##bit; break; \
- case BLEND_SUBTRACT: param->blend = blend_subtract_##depth##bit; break; \
+ case BLEND_SUBTRACT: param->blend = blend_subtract_##nbits##bit; break; \
case BLEND_VIVIDLIGHT: param->blend = blend_vividlight_##depth##bit; break; \
- case BLEND_XOR: param->blend = blend_xor_##depth##bit; break; \
+ case BLEND_XOR: param->blend = blend_xor_##nbits##bit; break; \
case BLEND_SOFTDIFFERENCE:param->blend=blend_softdifference_##depth##bit;break; \
- case BLEND_GEOMETRIC: param->blend = blend_geometric_##depth##bit; break; \
- case BLEND_HARMONIC: param->blend = blend_harmonic_##depth##bit; break; \
+ case BLEND_GEOMETRIC: param->blend = blend_geometric_##nbits##bit; break; \
+ case BLEND_HARMONIC: param->blend = blend_harmonic_##nbits##bit; break; \
case BLEND_BLEACH: param->blend = blend_bleach_##depth##bit; break; \
case BLEND_STAIN: param->blend = blend_stain_##depth##bit; break; \
case BLEND_INTERPOLATE: param->blend = blend_interpolate_##depth##bit; break; \
--
2.49.1
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