From: Jun Zhao via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>
To: ffmpeg-devel@ffmpeg.org
Cc: Jun Zhao <code@ffmpeg.org>
Subject: [FFmpeg-devel] [PR] hevc_dequant_opt (PR #21495)
Date: Fri, 16 Jan 2026 17:03:41 -0000
Message-ID: <176858302238.25.5707616102572168293@4457048688e7> (raw)
PR #21495 opened by Jun Zhao (mypopydev)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21495
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21495.patch
This patch series adds NEON-optimized HEVC dequantization for AArch64, covering 8-bit, 10-bit, and 12-bit depths.
All implementations are benchmarked on Apple M4, with performance data verified through 10-run averages using checkasm.
>From 51c1e4c124494fecf53aab8b89679dd4d4ce993b Mon Sep 17 00:00:00 2001
From: Jun Zhao <barryjzhao@tencent.com>
Date: Wed, 7 Jan 2026 07:50:13 +0800
Subject: [PATCH 1/4] lavc/hevc: add aarch64 neon for 8-bit dequant
Implement NEON optimization for HEVC dequant at 8-bit depth.
The NEON implementation uses srshr (Signed Rounding Shift Right) which
does both the add with offset and right shift in a single instruction.
Optimization details:
- 4x4 (16 coeffs): Single load-process-store sequence
- 8x8 (64 coeffs): Fully unrolled, no loop overhead
- 16x16 (256 coeffs): Loop with 64 coeffs per iteration
- 32x32 (1024 coeffs): Loop with 128 coeffs per iteration, using all
available NEON registers
Performance benchmark on Apple M4:
./tests/checkasm/checkasm --test=hevc_dequant --bench
hevc_dequant_4x4_8_c: 12.0 ( 1.00x)
hevc_dequant_4x4_8_neon: 6.9 ( 1.73x)
hevc_dequant_8x8_8_c: 37.1 ( 1.00x)
hevc_dequant_8x8_8_neon: 7.3 ( 5.11x)
hevc_dequant_16x16_8_c: 165.4 ( 1.00x)
hevc_dequant_16x16_8_neon: 13.3 (12.42x)
hevc_dequant_32x32_8_c: 86.0 ( 1.00x)
hevc_dequant_32x32_8_neon: 35.0 ( 2.45x)
Note on Performance Anomaly:
The observation that hevc_dequant_32x32_8_c is faster than 16x16 (86.0 vs 165.4)
is due to Clang auto-vectorizing only for sizes >= 32x32.
Compiler: Apple clang version 17.0.0 (clang-1700.6.3.2)
Signed-off-by: Jun Zhao <barryjzhao@tencent.com>
---
libavcodec/aarch64/Makefile | 1 +
libavcodec/aarch64/hevcdsp_dequant_neon.S | 177 ++++++++++++++++++++++
libavcodec/aarch64/hevcdsp_init_aarch64.c | 16 ++
tests/checkasm/Makefile | 2 +-
tests/checkasm/checkasm.c | 1 +
tests/checkasm/checkasm.h | 1 +
tests/checkasm/hevc_dequant.c | 76 ++++++++++
7 files changed, 273 insertions(+), 1 deletion(-)
create mode 100644 libavcodec/aarch64/hevcdsp_dequant_neon.S
create mode 100644 tests/checkasm/hevc_dequant.c
diff --git a/libavcodec/aarch64/Makefile b/libavcodec/aarch64/Makefile
index 2bf48dfa28..1e838ad901 100644
--- a/libavcodec/aarch64/Makefile
+++ b/libavcodec/aarch64/Makefile
@@ -71,6 +71,7 @@ NEON-OBJS-$(CONFIG_VP9_DECODER) += aarch64/vp9itxfm_16bpp_neon.o \
aarch64/vp9mc_16bpp_neon.o \
aarch64/vp9mc_neon.o
NEON-OBJS-$(CONFIG_HEVC_DECODER) += aarch64/hevcdsp_deblock_neon.o \
+ aarch64/hevcdsp_dequant_neon.o \
aarch64/hevcdsp_idct_neon.o \
aarch64/hevcdsp_init_aarch64.o \
aarch64/h26x/epel_neon.o \
diff --git a/libavcodec/aarch64/hevcdsp_dequant_neon.S b/libavcodec/aarch64/hevcdsp_dequant_neon.S
new file mode 100644
index 0000000000..f352f43e15
--- /dev/null
+++ b/libavcodec/aarch64/hevcdsp_dequant_neon.S
@@ -0,0 +1,177 @@
+/*
+ * ARM NEON optimised dequant functions for HEVC decoding
+ *
+ * Copyright (c) 2026 FFmpeg contributors
+ *
+ * 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/aarch64/asm.S"
+
+// HEVC dequant for 8-bit depth
+//
+// Algorithm (from dsp_template.c):
+// shift = 15 - BIT_DEPTH - log2_size
+// offset = 1 << (shift - 1)
+// output = (input + offset) >> shift
+//
+// This is equivalent to: output = ROUND(input >> shift)
+// NEON srshr (Signed Rounding Shift Right) does exactly this in one instruction!
+//
+// For 8-bit: shift = 15 - 8 - log2_size = 7 - log2_size
+//
+// Block size | log2_size | shift | operation
+// 4x4 | 2 | 5 | srshr #5
+// 8x8 | 3 | 4 | srshr #4
+// 16x16 | 4 | 3 | srshr #3
+// 32x32 | 5 | 2 | srshr #2
+
+// void ff_hevc_dequant_4x4_8_neon(int16_t *coeffs, int16_t log2_size)
+// 4x4 = 16 coeffs, shift=5
+// Note: log2_size parameter (x1) is unused; shift value is hardcoded for performance
+function ff_hevc_dequant_4x4_8_neon, export=1
+ ldp q0, q1, [x0] // load 16 int16_t (32 bytes)
+ srshr v0.8h, v0.8h, #5 // rounding shift right by 5
+ srshr v1.8h, v1.8h, #5
+ stp q0, q1, [x0] // store
+ ret
+endfunc
+
+// void ff_hevc_dequant_8x8_8_neon(int16_t *coeffs, int16_t log2_size)
+// 8x8 = 64 coeffs, shift=4
+// Fully unrolled - no loop needed for 64 coeffs
+// Note: log2_size parameter (x1) is unused; shift value is hardcoded for performance
+function ff_hevc_dequant_8x8_8_neon, export=1
+ ldp q0, q1, [x0]
+ ldp q2, q3, [x0, #32]
+ ldp q4, q5, [x0, #64]
+ ldp q6, q7, [x0, #96]
+ srshr v0.8h, v0.8h, #4
+ srshr v1.8h, v1.8h, #4
+ srshr v2.8h, v2.8h, #4
+ srshr v3.8h, v3.8h, #4
+ srshr v4.8h, v4.8h, #4
+ srshr v5.8h, v5.8h, #4
+ srshr v6.8h, v6.8h, #4
+ srshr v7.8h, v7.8h, #4
+ stp q0, q1, [x0]
+ stp q2, q3, [x0, #32]
+ stp q4, q5, [x0, #64]
+ stp q6, q7, [x0, #96]
+ ret
+endfunc
+
+// void ff_hevc_dequant_16x16_8_neon(int16_t *coeffs, int16_t log2_size)
+// 16x16 = 256 coeffs, shift=3
+// Process 64 coeffs per iteration (4 iterations)
+// Note: log2_size parameter (x1) is unused; shift value is hardcoded for performance
+function ff_hevc_dequant_16x16_8_neon, export=1
+ mov x2, #4 // loop 4 times (64 coeffs each)
+1:
+ ldp q0, q1, [x0]
+ ldp q2, q3, [x0, #32]
+ ldp q4, q5, [x0, #64]
+ ldp q6, q7, [x0, #96]
+ srshr v0.8h, v0.8h, #3
+ srshr v1.8h, v1.8h, #3
+ srshr v2.8h, v2.8h, #3
+ srshr v3.8h, v3.8h, #3
+ srshr v4.8h, v4.8h, #3
+ srshr v5.8h, v5.8h, #3
+ srshr v6.8h, v6.8h, #3
+ srshr v7.8h, v7.8h, #3
+ stp q0, q1, [x0]
+ stp q2, q3, [x0, #32]
+ stp q4, q5, [x0, #64]
+ stp q6, q7, [x0, #96]
+ add x0, x0, #128
+ subs x2, x2, #1
+ b.ne 1b
+ ret
+endfunc
+
+// void ff_hevc_dequant_32x32_8_neon(int16_t *coeffs, int16_t log2_size)
+// 32x32 = 1024 coeffs, shift=2
+// Process 128 coeffs per iteration (8 iterations)
+// Using all available NEON registers for maximum throughput
+// AAPCS64: v0-v7 and v16-v31 are volatile (caller-saved)
+// We use v0-v7 and v16-v23 to avoid touching callee-saved v8-v15
+// Note: log2_size parameter (x1) is unused; shift value is hardcoded for performance
+function ff_hevc_dequant_32x32_8_neon, export=1
+ mov x2, #8 // loop 8 times (128 coeffs each)
+1:
+ // Group A: q0-q3 (64 bytes / 32 coeffs)
+ ldp q0, q1, [x0]
+ ldp q2, q3, [x0, #32]
+ // Group B: q4-q7 (64 bytes / 32 coeffs)
+ ldp q4, q5, [x0, #64]
+ ldp q6, q7, [x0, #96]
+
+ // Calc Group A (shift right with rounding)
+ srshr v0.8h, v0.8h, #2
+ srshr v1.8h, v1.8h, #2
+ srshr v2.8h, v2.8h, #2
+ srshr v3.8h, v3.8h, #2
+
+ // Group C: q16-q19 (64 bytes / 32 coeffs)
+ // Load into volatile high registers to maximize pipeline usage
+ ldp q16, q17, [x0, #128]
+ ldp q18, q19, [x0, #160]
+
+ // Calc Group B
+ srshr v4.8h, v4.8h, #2
+ srshr v5.8h, v5.8h, #2
+ srshr v6.8h, v6.8h, #2
+ srshr v7.8h, v7.8h, #2
+
+ // Store Group A (Write back results to memory)
+ stp q0, q1, [x0]
+ stp q2, q3, [x0, #32]
+
+ // Group D: q20-q23 (64 bytes / 32 coeffs)
+ ldp q20, q21, [x0, #192]
+ ldp q22, q23, [x0, #224]
+
+ // Calc Group C
+ srshr v16.8h, v16.8h, #2
+ srshr v17.8h, v17.8h, #2
+ srshr v18.8h, v18.8h, #2
+ srshr v19.8h, v19.8h, #2
+
+ // Store Group B
+ stp q4, q5, [x0, #64]
+ stp q6, q7, [x0, #96]
+
+ // Calc Group D
+ srshr v20.8h, v20.8h, #2
+ srshr v21.8h, v21.8h, #2
+ srshr v22.8h, v22.8h, #2
+ srshr v23.8h, v23.8h, #2
+
+ // Store Group C
+ stp q16, q17, [x0, #128]
+ stp q18, q19, [x0, #160]
+
+ // Store Group D
+ stp q20, q21, [x0, #192]
+ stp q22, q23, [x0, #224]
+
+ add x0, x0, #256 // Advance pointer by 128 coeffs (256 bytes)
+ subs x2, x2, #1
+ b.ne 1b
+ ret
+endfunc
diff --git a/libavcodec/aarch64/hevcdsp_init_aarch64.c b/libavcodec/aarch64/hevcdsp_init_aarch64.c
index 8dec58bc7f..0d1e1dcfeb 100644
--- a/libavcodec/aarch64/hevcdsp_init_aarch64.c
+++ b/libavcodec/aarch64/hevcdsp_init_aarch64.c
@@ -97,6 +97,21 @@ void ff_hevc_idct_16x16_dc_12_neon(int16_t *coeffs);
void ff_hevc_idct_32x32_dc_12_neon(int16_t *coeffs);
void ff_hevc_transform_luma_4x4_neon_8(int16_t *coeffs);
+void ff_hevc_dequant_4x4_8_neon(int16_t *coeffs, int16_t log2_size);
+void ff_hevc_dequant_8x8_8_neon(int16_t *coeffs, int16_t log2_size);
+void ff_hevc_dequant_16x16_8_neon(int16_t *coeffs, int16_t log2_size);
+void ff_hevc_dequant_32x32_8_neon(int16_t *coeffs, int16_t log2_size);
+
+static void ff_hevc_dequant_8_neon(int16_t *coeffs, int16_t log2_size)
+{
+ switch (log2_size) {
+ case 2: ff_hevc_dequant_4x4_8_neon(coeffs, log2_size); break;
+ case 3: ff_hevc_dequant_8x8_8_neon(coeffs, log2_size); break;
+ case 4: ff_hevc_dequant_16x16_8_neon(coeffs, log2_size); break;
+ case 5: ff_hevc_dequant_32x32_8_neon(coeffs, log2_size); break;
+ }
+}
+
#define NEON8_FNASSIGN(member, v, h, fn, ext) \
member[1][v][h] = ff_hevc_put_hevc_##fn##4_8_neon##ext; \
member[2][v][h] = ff_hevc_put_hevc_##fn##6_8_neon##ext; \
@@ -168,6 +183,7 @@ av_cold void ff_hevc_dsp_init_aarch64(HEVCDSPContext *c, const int bit_depth)
c->idct_dc[2] = ff_hevc_idct_16x16_dc_8_neon;
c->idct_dc[3] = ff_hevc_idct_32x32_dc_8_neon;
c->transform_4x4_luma = ff_hevc_transform_luma_4x4_neon_8;
+ c->dequant = ff_hevc_dequant_8_neon;
c->sao_band_filter[0] = ff_h26x_sao_band_filter_8x8_8_neon;
c->sao_band_filter[1] =
c->sao_band_filter[2] =
diff --git a/tests/checkasm/Makefile b/tests/checkasm/Makefile
index 48f358d40d..f4ac5a940f 100644
--- a/tests/checkasm/Makefile
+++ b/tests/checkasm/Makefile
@@ -42,7 +42,7 @@ AVCODECOBJS-$(CONFIG_HUFFYUV_DECODER) += huffyuvdsp.o
AVCODECOBJS-$(CONFIG_JPEG2000_DECODER) += jpeg2000dsp.o
AVCODECOBJS-$(CONFIG_OPUS_DECODER) += opusdsp.o
AVCODECOBJS-$(CONFIG_PIXBLOCKDSP) += pixblockdsp.o
-AVCODECOBJS-$(CONFIG_HEVC_DECODER) += hevc_add_res.o hevc_deblock.o hevc_idct.o hevc_sao.o hevc_pel.o
+AVCODECOBJS-$(CONFIG_HEVC_DECODER) += hevc_add_res.o hevc_deblock.o hevc_dequant.o hevc_idct.o hevc_sao.o hevc_pel.o
AVCODECOBJS-$(CONFIG_RV34DSP) += rv34dsp.o
AVCODECOBJS-$(CONFIG_RV40_DECODER) += rv40dsp.o
AVCODECOBJS-$(CONFIG_SVQ1_ENCODER) += svq1enc.o
diff --git a/tests/checkasm/checkasm.c b/tests/checkasm/checkasm.c
index 7dcdaeb2a4..f9ccb30ce9 100644
--- a/tests/checkasm/checkasm.c
+++ b/tests/checkasm/checkasm.c
@@ -187,6 +187,7 @@ static const struct {
#if CONFIG_HEVC_DECODER
{ "hevc_add_res", checkasm_check_hevc_add_res },
{ "hevc_deblock", checkasm_check_hevc_deblock },
+ { "hevc_dequant", checkasm_check_hevc_dequant },
{ "hevc_idct", checkasm_check_hevc_idct },
{ "hevc_pel", checkasm_check_hevc_pel },
{ "hevc_sao", checkasm_check_hevc_sao },
diff --git a/tests/checkasm/checkasm.h b/tests/checkasm/checkasm.h
index e3addec21e..b246d0c4da 100644
--- a/tests/checkasm/checkasm.h
+++ b/tests/checkasm/checkasm.h
@@ -110,6 +110,7 @@ void checkasm_check_h264pred(void);
void checkasm_check_h264qpel(void);
void checkasm_check_hevc_add_res(void);
void checkasm_check_hevc_deblock(void);
+void checkasm_check_hevc_dequant(void);
void checkasm_check_hevc_idct(void);
void checkasm_check_hevc_pel(void);
void checkasm_check_hevc_sao(void);
diff --git a/tests/checkasm/hevc_dequant.c b/tests/checkasm/hevc_dequant.c
new file mode 100644
index 0000000000..20e322994a
--- /dev/null
+++ b/tests/checkasm/hevc_dequant.c
@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2024 FFmpeg contributors
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU 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 <string.h>
+
+#include "libavutil/intreadwrite.h"
+#include "libavutil/mem_internal.h"
+
+#include "libavcodec/hevc/dsp.h"
+
+#include "checkasm.h"
+
+#define randomize_buffers(buf, size) \
+ do { \
+ int j; \
+ for (j = 0; j < size; j++) { \
+ int16_t r = rnd() & 0x7FFF; \
+ if (rnd() & 1) r = -r; \
+ AV_WN16A(buf + j, r); \
+ } \
+ } while (0)
+
+static void check_dequant(HEVCDSPContext *h, int bit_depth)
+{
+ int i;
+ LOCAL_ALIGNED(32, int16_t, coeffs0, [32 * 32]);
+ LOCAL_ALIGNED(32, int16_t, coeffs1, [32 * 32]);
+
+ for (i = 2; i <= 5; i++) {
+ int block_size = 1 << i;
+ int size = block_size * block_size;
+ declare_func(void, int16_t *coeffs, int16_t log2_size);
+
+ randomize_buffers(coeffs0, size);
+ memcpy(coeffs1, coeffs0, sizeof(*coeffs0) * size);
+
+ if (check_func(h->dequant, "hevc_dequant_%dx%d_%d",
+ block_size, block_size, bit_depth)) {
+ call_ref(coeffs0, i);
+ call_new(coeffs1, i);
+ if (memcmp(coeffs0, coeffs1, sizeof(*coeffs0) * size))
+ fail();
+ bench_new(coeffs1, i);
+ }
+ }
+}
+
+void checkasm_check_hevc_dequant(void)
+{
+ int bit_depth;
+
+ for (bit_depth = 8; bit_depth <= 12; bit_depth += 2) {
+ HEVCDSPContext h;
+
+ ff_hevc_dsp_init(&h, bit_depth);
+ check_dequant(&h, bit_depth);
+ }
+ report("dequant");
+}
--
2.52.0
>From 100ad43bb82078c23be654cb03f296ff033ad7c0 Mon Sep 17 00:00:00 2001
From: Jun Zhao <barryjzhao@tencent.com>
Date: Fri, 16 Jan 2026 21:38:27 +0800
Subject: [PATCH 2/4] lavc/hevc: optimize dequant for shift=0 case (identity
transform)
The HEVC dequantization uses:
shift = 15 - bit_depth - log2_size
When shift equals 0, the operation becomes an identity transform:
- For shift > 0: output = (input + offset) >> shift
- For shift < 0: output = input << (-shift)
- For shift = 0: output = input << 0 = input (no change)
This occurs in the following cases:
- 10-bit, 32x32 block: shift = 15 - 10 - 5 = 0
- 12-bit, 8x8 block: shift = 15 - 12 - 3 = 0
Previously, the code would still iterate through all coefficients
and perform redundant read-modify-write operations even when shift=0.
This patch adds an early return for shift=0, avoiding unnecessary
memory operations. checkasm benchmarks on Apple M4 show:
- 10-bit 32x32: 69.1 -> 1.6 cycles (43x faster)
- 12-bit 8x8: 30.9 -> 1.7 cycles (18x faster)
Signed-off-by: Jun Zhao <barryjzhao@tencent.com>
---
libavcodec/hevc/dsp_template.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)
diff --git a/libavcodec/hevc/dsp_template.c b/libavcodec/hevc/dsp_template.c
index a0f79c2673..ed0bd63d71 100644
--- a/libavcodec/hevc/dsp_template.c
+++ b/libavcodec/hevc/dsp_template.c
@@ -106,6 +106,26 @@ static void FUNC(transform_rdpcm)(int16_t *_coeffs, int16_t log2_size, int mode)
}
}
+/**
+ * HEVC transform dequantization (ITU-T H.265 8.6.3)
+ *
+ * @param coeffs transform coefficient buffer (in-place)
+ * @param log2_size log2 of transform block size, range: 2..5 (4x4 to 32x32)
+ * This value comes from recursive split_transform_flag parsing
+ * in the bitstream, bounded by log2_min_tb_size (min 2) and
+ * log2_max_trafo_size (max 5) from SPS.
+ *
+ * Formula: shift = 15 - BIT_DEPTH - log2_size
+ *
+ * bit_depth | 4x4 (2) | 8x8 (3) | 16x16 (4) | 32x32 (5)
+ * ----------+---------+---------+-----------+----------
+ * 8-bit | 5 | 4 | 3 | 2 (shift right)
+ * 10-bit | 3 | 2 | 1 | 0 (shift right / no-op)
+ * 12-bit | 1 | 0 | -1 | -2 (no-op / shift left)
+ *
+ * When shift == 0, output equals input (identity transform), so we skip
+ * the loop entirely for better performance.
+ */
static void FUNC(dequant)(int16_t *coeffs, int16_t log2_size)
{
int shift = 15 - BIT_DEPTH - log2_size;
@@ -120,7 +140,7 @@ static void FUNC(dequant)(int16_t *coeffs, int16_t log2_size)
coeffs++;
}
}
- } else {
+ } else if (shift < 0) {
for (y = 0; y < size; y++) {
for (x = 0; x < size; x++) {
*coeffs = *(uint16_t*)coeffs << -shift;
@@ -128,6 +148,7 @@ static void FUNC(dequant)(int16_t *coeffs, int16_t log2_size)
}
}
}
+ /* shift == 0: no operation needed (identity transform) */
}
#define SET(dst, x) (dst) = (x)
--
2.52.0
>From 4b372d119aeaa405281b93aa9c7e5a207304c842 Mon Sep 17 00:00:00 2001
From: Jun Zhao <barryjzhao@tencent.com>
Date: Fri, 16 Jan 2026 22:05:58 +0800
Subject: [PATCH 3/4] lavc/hevc: add aarch64 neon for 10-bit dequant
Add NEON optimized dequantization for 10-bit HEVC.
For 10-bit: shift = 15 - 10 - log2_size = 5 - log2_size
Block size | shift | operation
-----------+-------+-----------
4x4 | 3 | srshr #3
8x8 | 2 | srshr #2
16x16 | 1 | srshr #1
32x32 | 0 | no-op (identity, just return)
Performance benchmark on Apple M4:
./tests/checkasm/checkasm --test=hevc_dequant --bench
hevc_dequant_4x4_10_c: 9.7 ( 1.00x)
hevc_dequant_4x4_10_neon: 5.6 ( 1.73x)
hevc_dequant_8x8_10_c: 30.3 ( 1.00x)
hevc_dequant_8x8_10_neon: 5.9 ( 5.14x)
hevc_dequant_16x16_10_c: 129.9 ( 1.00x)
hevc_dequant_16x16_10_neon: 10.6 (12.25x)
hevc_dequant_32x32_10_c: 1.6 ( 1.00x)
hevc_dequant_32x32_10_neon: 1.7 ( 0.94x)
Note: 32x32 shows no improvement because shift=0 triggers the
identity transform optimization (no processing needed).
Signed-off-by: Jun Zhao <barryjzhao@tencent.com>
---
libavcodec/aarch64/hevcdsp_dequant_neon.S | 85 +++++++++++++++++++++++
libavcodec/aarch64/hevcdsp_init_aarch64.c | 16 +++++
2 files changed, 101 insertions(+)
diff --git a/libavcodec/aarch64/hevcdsp_dequant_neon.S b/libavcodec/aarch64/hevcdsp_dequant_neon.S
index f352f43e15..3b016b839b 100644
--- a/libavcodec/aarch64/hevcdsp_dequant_neon.S
+++ b/libavcodec/aarch64/hevcdsp_dequant_neon.S
@@ -175,3 +175,88 @@ function ff_hevc_dequant_32x32_8_neon, export=1
b.ne 1b
ret
endfunc
+
+// --------------------------------------------------------------------------
+// HEVC dequant for 10-bit depth
+//
+// For 10-bit: shift = 15 - 10 - log2_size = 5 - log2_size
+//
+// Block size | log2_size | shift | operation
+// 4x4 | 2 | 3 | srshr #3
+// 8x8 | 3 | 2 | srshr #2
+// 16x16 | 4 | 1 | srshr #1
+// 32x32 | 5 | 0 | no-op (identity)
+// --------------------------------------------------------------------------
+
+// void ff_hevc_dequant_4x4_10_neon(int16_t *coeffs, int16_t log2_size)
+// 4x4 = 16 coeffs, shift=3
+// Note: log2_size parameter (x1) is unused; shift value is hardcoded for performance
+function ff_hevc_dequant_4x4_10_neon, export=1
+ ldp q0, q1, [x0]
+ srshr v0.8h, v0.8h, #3
+ srshr v1.8h, v1.8h, #3
+ stp q0, q1, [x0]
+ ret
+endfunc
+
+// void ff_hevc_dequant_8x8_10_neon(int16_t *coeffs, int16_t log2_size)
+// 8x8 = 64 coeffs, shift=2
+// Fully unrolled - no loop needed for 64 coeffs
+// Note: log2_size parameter (x1) is unused; shift value is hardcoded for performance
+function ff_hevc_dequant_8x8_10_neon, export=1
+ ldp q0, q1, [x0]
+ ldp q2, q3, [x0, #32]
+ ldp q4, q5, [x0, #64]
+ ldp q6, q7, [x0, #96]
+ srshr v0.8h, v0.8h, #2
+ srshr v1.8h, v1.8h, #2
+ srshr v2.8h, v2.8h, #2
+ srshr v3.8h, v3.8h, #2
+ srshr v4.8h, v4.8h, #2
+ srshr v5.8h, v5.8h, #2
+ srshr v6.8h, v6.8h, #2
+ srshr v7.8h, v7.8h, #2
+ stp q0, q1, [x0]
+ stp q2, q3, [x0, #32]
+ stp q4, q5, [x0, #64]
+ stp q6, q7, [x0, #96]
+ ret
+endfunc
+
+// void ff_hevc_dequant_16x16_10_neon(int16_t *coeffs, int16_t log2_size)
+// 16x16 = 256 coeffs, shift=1
+// Process 64 coeffs per iteration (4 iterations)
+// Note: log2_size parameter (x1) is unused; shift value is hardcoded for performance
+function ff_hevc_dequant_16x16_10_neon, export=1
+ mov x2, #4
+1:
+ ldp q0, q1, [x0]
+ ldp q2, q3, [x0, #32]
+ ldp q4, q5, [x0, #64]
+ ldp q6, q7, [x0, #96]
+ srshr v0.8h, v0.8h, #1
+ srshr v1.8h, v1.8h, #1
+ srshr v2.8h, v2.8h, #1
+ srshr v3.8h, v3.8h, #1
+ srshr v4.8h, v4.8h, #1
+ srshr v5.8h, v5.8h, #1
+ srshr v6.8h, v6.8h, #1
+ srshr v7.8h, v7.8h, #1
+ stp q0, q1, [x0]
+ stp q2, q3, [x0, #32]
+ stp q4, q5, [x0, #64]
+ stp q6, q7, [x0, #96]
+ add x0, x0, #128
+ subs x2, x2, #1
+ b.ne 1b
+ ret
+endfunc
+
+// void ff_hevc_dequant_32x32_10_neon(int16_t *coeffs, int16_t log2_size)
+// 32x32 = 1024 coeffs, shift=0
+// When shift=0: output = (input + 0) >> 0 = input (identity transform)
+// No operation needed - just return immediately
+// Note: log2_size parameter (x1) is unused
+function ff_hevc_dequant_32x32_10_neon, export=1
+ ret
+endfunc
diff --git a/libavcodec/aarch64/hevcdsp_init_aarch64.c b/libavcodec/aarch64/hevcdsp_init_aarch64.c
index 0d1e1dcfeb..d5eb218e64 100644
--- a/libavcodec/aarch64/hevcdsp_init_aarch64.c
+++ b/libavcodec/aarch64/hevcdsp_init_aarch64.c
@@ -102,6 +102,11 @@ void ff_hevc_dequant_8x8_8_neon(int16_t *coeffs, int16_t log2_size);
void ff_hevc_dequant_16x16_8_neon(int16_t *coeffs, int16_t log2_size);
void ff_hevc_dequant_32x32_8_neon(int16_t *coeffs, int16_t log2_size);
+void ff_hevc_dequant_4x4_10_neon(int16_t *coeffs, int16_t log2_size);
+void ff_hevc_dequant_8x8_10_neon(int16_t *coeffs, int16_t log2_size);
+void ff_hevc_dequant_16x16_10_neon(int16_t *coeffs, int16_t log2_size);
+void ff_hevc_dequant_32x32_10_neon(int16_t *coeffs, int16_t log2_size);
+
static void ff_hevc_dequant_8_neon(int16_t *coeffs, int16_t log2_size)
{
switch (log2_size) {
@@ -112,6 +117,16 @@ static void ff_hevc_dequant_8_neon(int16_t *coeffs, int16_t log2_size)
}
}
+static void ff_hevc_dequant_10_neon(int16_t *coeffs, int16_t log2_size)
+{
+ switch (log2_size) {
+ case 2: ff_hevc_dequant_4x4_10_neon(coeffs, log2_size); break;
+ case 3: ff_hevc_dequant_8x8_10_neon(coeffs, log2_size); break;
+ case 4: ff_hevc_dequant_16x16_10_neon(coeffs, log2_size); break;
+ case 5: ff_hevc_dequant_32x32_10_neon(coeffs, log2_size); break;
+ }
+}
+
#define NEON8_FNASSIGN(member, v, h, fn, ext) \
member[1][v][h] = ff_hevc_put_hevc_##fn##4_8_neon##ext; \
member[2][v][h] = ff_hevc_put_hevc_##fn##6_8_neon##ext; \
@@ -290,6 +305,7 @@ av_cold void ff_hevc_dsp_init_aarch64(HEVCDSPContext *c, const int bit_depth)
c->idct_dc[1] = ff_hevc_idct_8x8_dc_10_neon;
c->idct_dc[2] = ff_hevc_idct_16x16_dc_10_neon;
c->idct_dc[3] = ff_hevc_idct_32x32_dc_10_neon;
+ c->dequant = ff_hevc_dequant_10_neon;
}
if (bit_depth == 12) {
c->hevc_h_loop_filter_luma = ff_hevc_h_loop_filter_luma_12_neon;
--
2.52.0
>From d02c79573c29519ce83fe20969b90fa0b1f702f6 Mon Sep 17 00:00:00 2001
From: Jun Zhao <barryjzhao@tencent.com>
Date: Fri, 16 Jan 2026 22:19:27 +0800
Subject: [PATCH 4/4] lavc/hevc: add aarch64 neon for 12-bit dequant
Add NEON optimizations for HEVC 12-bit dequantization.
For 12-bit: shift = 15 - 12 - log2_size = 3 - log2_size
Block size | log2_size | shift | operation
-----------+-----------+-------+-----------
4x4 | 2 | 1 | srshr #1 (shift right with rounding)
8x8 | 3 | 0 | identity (no-op, just return)
16x16 | 4 | -1 | shl #1 (shift left)
32x32 | 5 | -2 | shl #2 (shift left)
Performance benchmark on Apple M4:
./tests/checkasm/checkasm --test=hevc_dequant --bench
hevc_dequant_4x4_12_c: 9.8 ( 1.00x)
hevc_dequant_4x4_12_neon: 5.8 ( 1.70x)
hevc_dequant_8x8_12_c: 1.7 ( 1.00x)
hevc_dequant_8x8_12_neon: 1.3 ( 1.34x)
hevc_dequant_16x16_12_c: 133.9 ( 1.00x)
hevc_dequant_16x16_12_neon: 11.0 (12.20x)
hevc_dequant_32x32_12_c: 70.1 ( 1.00x)
hevc_dequant_32x32_12_neon: 29.0 ( 2.42x)
Note: 8x8 shows minimal improvement because shift=0 triggers the
identity transform optimization (limited processing needed).
Signed-off-by: Jun Zhao <barryjzhao@tencent.com>
---
libavcodec/aarch64/hevcdsp_dequant_neon.S | 130 ++++++++++++++++++++++
libavcodec/aarch64/hevcdsp_init_aarch64.c | 16 +++
2 files changed, 146 insertions(+)
diff --git a/libavcodec/aarch64/hevcdsp_dequant_neon.S b/libavcodec/aarch64/hevcdsp_dequant_neon.S
index 3b016b839b..c0b5f3fab4 100644
--- a/libavcodec/aarch64/hevcdsp_dequant_neon.S
+++ b/libavcodec/aarch64/hevcdsp_dequant_neon.S
@@ -260,3 +260,133 @@ endfunc
function ff_hevc_dequant_32x32_10_neon, export=1
ret
endfunc
+
+// --------------------------------------------------------------------------
+// HEVC dequant for 12-bit depth
+//
+// For 12-bit: shift = 15 - 12 - log2_size = 3 - log2_size
+//
+// Block size | log2_size | shift | operation
+// 4x4 | 2 | 1 | srshr #1 (shift right)
+// 8x8 | 3 | 0 | no-op (identity)
+// 16x16 | 4 | -1 | shl #1 (shift left)
+// 32x32 | 5 | -2 | shl #2 (shift left)
+// --------------------------------------------------------------------------
+
+// void ff_hevc_dequant_4x4_12_neon(int16_t *coeffs, int16_t log2_size)
+// 4x4 = 16 coeffs, shift=1
+// Note: log2_size parameter (x1) is unused; shift value is hardcoded for performance
+function ff_hevc_dequant_4x4_12_neon, export=1
+ ldp q0, q1, [x0]
+ srshr v0.8h, v0.8h, #1
+ srshr v1.8h, v1.8h, #1
+ stp q0, q1, [x0]
+ ret
+endfunc
+
+// void ff_hevc_dequant_8x8_12_neon(int16_t *coeffs, int16_t log2_size)
+// 8x8 = 64 coeffs, shift=0
+// When shift=0: output = input (identity transform)
+// No operation needed - just return immediately
+// Note: log2_size parameter (x1) is unused
+function ff_hevc_dequant_8x8_12_neon, export=1
+ ret
+endfunc
+
+// void ff_hevc_dequant_16x16_12_neon(int16_t *coeffs, int16_t log2_size)
+// 16x16 = 256 coeffs, shift=-1 (left shift by 1)
+// Process 64 coeffs per iteration (4 iterations)
+// Note: log2_size parameter (x1) is unused; shift value is hardcoded for performance
+function ff_hevc_dequant_16x16_12_neon, export=1
+ mov x2, #4
+1:
+ ldp q0, q1, [x0]
+ ldp q2, q3, [x0, #32]
+ ldp q4, q5, [x0, #64]
+ ldp q6, q7, [x0, #96]
+ shl v0.8h, v0.8h, #1
+ shl v1.8h, v1.8h, #1
+ shl v2.8h, v2.8h, #1
+ shl v3.8h, v3.8h, #1
+ shl v4.8h, v4.8h, #1
+ shl v5.8h, v5.8h, #1
+ shl v6.8h, v6.8h, #1
+ shl v7.8h, v7.8h, #1
+ stp q0, q1, [x0]
+ stp q2, q3, [x0, #32]
+ stp q4, q5, [x0, #64]
+ stp q6, q7, [x0, #96]
+ add x0, x0, #128
+ subs x2, x2, #1
+ b.ne 1b
+ ret
+endfunc
+
+// void ff_hevc_dequant_32x32_12_neon(int16_t *coeffs, int16_t log2_size)
+// 32x32 = 1024 coeffs, shift=-2 (left shift by 2)
+// Process 128 coeffs per iteration (8 iterations)
+// Using pipelined load/compute/store for better performance
+// Note: log2_size parameter (x1) is unused; shift value is hardcoded for performance
+function ff_hevc_dequant_32x32_12_neon, export=1
+ mov x2, #8
+1:
+ // Group A: q0-q3 (64 bytes / 32 coeffs)
+ ldp q0, q1, [x0]
+ ldp q2, q3, [x0, #32]
+ // Group B: q4-q7 (64 bytes / 32 coeffs)
+ ldp q4, q5, [x0, #64]
+ ldp q6, q7, [x0, #96]
+
+ // Calc Group A (shift left by 2)
+ shl v0.8h, v0.8h, #2
+ shl v1.8h, v1.8h, #2
+ shl v2.8h, v2.8h, #2
+ shl v3.8h, v3.8h, #2
+
+ // Group C: q16-q19 (64 bytes / 32 coeffs)
+ ldp q16, q17, [x0, #128]
+ ldp q18, q19, [x0, #160]
+
+ // Calc Group B
+ shl v4.8h, v4.8h, #2
+ shl v5.8h, v5.8h, #2
+ shl v6.8h, v6.8h, #2
+ shl v7.8h, v7.8h, #2
+
+ // Store Group A
+ stp q0, q1, [x0]
+ stp q2, q3, [x0, #32]
+
+ // Group D: q20-q23 (64 bytes / 32 coeffs)
+ ldp q20, q21, [x0, #192]
+ ldp q22, q23, [x0, #224]
+
+ // Calc Group C
+ shl v16.8h, v16.8h, #2
+ shl v17.8h, v17.8h, #2
+ shl v18.8h, v18.8h, #2
+ shl v19.8h, v19.8h, #2
+
+ // Store Group B
+ stp q4, q5, [x0, #64]
+ stp q6, q7, [x0, #96]
+
+ // Calc Group D
+ shl v20.8h, v20.8h, #2
+ shl v21.8h, v21.8h, #2
+ shl v22.8h, v22.8h, #2
+ shl v23.8h, v23.8h, #2
+
+ // Store Group C
+ stp q16, q17, [x0, #128]
+ stp q18, q19, [x0, #160]
+
+ // Store Group D
+ stp q20, q21, [x0, #192]
+ stp q22, q23, [x0, #224]
+
+ add x0, x0, #256
+ subs x2, x2, #1
+ b.ne 1b
+ ret
+endfunc
diff --git a/libavcodec/aarch64/hevcdsp_init_aarch64.c b/libavcodec/aarch64/hevcdsp_init_aarch64.c
index d5eb218e64..376074fb47 100644
--- a/libavcodec/aarch64/hevcdsp_init_aarch64.c
+++ b/libavcodec/aarch64/hevcdsp_init_aarch64.c
@@ -107,6 +107,11 @@ void ff_hevc_dequant_8x8_10_neon(int16_t *coeffs, int16_t log2_size);
void ff_hevc_dequant_16x16_10_neon(int16_t *coeffs, int16_t log2_size);
void ff_hevc_dequant_32x32_10_neon(int16_t *coeffs, int16_t log2_size);
+void ff_hevc_dequant_4x4_12_neon(int16_t *coeffs, int16_t log2_size);
+void ff_hevc_dequant_8x8_12_neon(int16_t *coeffs, int16_t log2_size);
+void ff_hevc_dequant_16x16_12_neon(int16_t *coeffs, int16_t log2_size);
+void ff_hevc_dequant_32x32_12_neon(int16_t *coeffs, int16_t log2_size);
+
static void ff_hevc_dequant_8_neon(int16_t *coeffs, int16_t log2_size)
{
switch (log2_size) {
@@ -127,6 +132,16 @@ static void ff_hevc_dequant_10_neon(int16_t *coeffs, int16_t log2_size)
}
}
+static void ff_hevc_dequant_12_neon(int16_t *coeffs, int16_t log2_size)
+{
+ switch (log2_size) {
+ case 2: ff_hevc_dequant_4x4_12_neon(coeffs, log2_size); break;
+ case 3: ff_hevc_dequant_8x8_12_neon(coeffs, log2_size); break;
+ case 4: ff_hevc_dequant_16x16_12_neon(coeffs, log2_size); break;
+ case 5: ff_hevc_dequant_32x32_12_neon(coeffs, log2_size); break;
+ }
+}
+
#define NEON8_FNASSIGN(member, v, h, fn, ext) \
member[1][v][h] = ff_hevc_put_hevc_##fn##4_8_neon##ext; \
member[2][v][h] = ff_hevc_put_hevc_##fn##6_8_neon##ext; \
@@ -320,5 +335,6 @@ av_cold void ff_hevc_dsp_init_aarch64(HEVCDSPContext *c, const int bit_depth)
c->idct_dc[1] = ff_hevc_idct_8x8_dc_12_neon;
c->idct_dc[2] = ff_hevc_idct_16x16_dc_12_neon;
c->idct_dc[3] = ff_hevc_idct_32x32_dc_12_neon;
+ c->dequant = ff_hevc_dequant_12_neon;
}
}
--
2.52.0
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