[FFmpeg-devel] [PATCH 3/4] lavc/aarch64: add HEVC sao_band NEON

[Josh Dekker]

Only works for 8x8.

Signed-off-by: Josh Dekker <josh at itanimul.li>
---
 libavcodec/aarch64/Makefile           |  3 +-
 libavcodec/aarch64/hevcdsp_init.c     |  7 +++
 libavcodec/aarch64/hevcdsp_sao_neon.S | 87 +++++++++++++++++++++++++++
 3 files changed, 96 insertions(+), 1 deletion(-)
 create mode 100644 libavcodec/aarch64/hevcdsp_sao_neon.S

diff --git a/libavcodec/aarch64/Makefile b/libavcodec/aarch64/Makefile
index 42d80bf74c..1f54fc31f4 100644
--- a/libavcodec/aarch64/Makefile
+++ b/libavcodec/aarch64/Makefile
@@ -55,7 +55,8 @@ NEON-OBJS-$(CONFIG_VP8DSP)              += aarch64/vp8dsp_neon.o
 NEON-OBJS-$(CONFIG_AAC_DECODER)         += aarch64/aacpsdsp_neon.o
 NEON-OBJS-$(CONFIG_DCA_DECODER)         += aarch64/synth_filter_neon.o
 NEON-OBJS-$(CONFIG_HEVC_DECODER)        += aarch64/hevcdsp_add_res_neon.o      \
-                                           aarch64/hevcdsp_idct_neon.o
+                                           aarch64/hevcdsp_idct_neon.o         \
+                                           aarch64/hevcdsp_sao_neon.o
 NEON-OBJS-$(CONFIG_OPUS_DECODER)        += aarch64/opusdsp_neon.o
 NEON-OBJS-$(CONFIG_VORBIS_DECODER)      += aarch64/vorbisdsp_neon.o
 NEON-OBJS-$(CONFIG_VP9_DECODER)         += aarch64/vp9itxfm_16bpp_neon.o       \
diff --git a/libavcodec/aarch64/hevcdsp_init.c b/libavcodec/aarch64/hevcdsp_init.c
index 2cd7ef3a6c..8f0a923ab1 100644
--- a/libavcodec/aarch64/hevcdsp_init.c
+++ b/libavcodec/aarch64/hevcdsp_init.c
@@ -23,6 +23,11 @@
 #include "libavcodec/hevcdsp.h"
 #include "libavcodec/avcodec.h"
 
+void ff_hevc_sao_band_filter_8x8_8_neon(uint8_t *_dst, uint8_t *_src,
+                                  ptrdiff_t stride_dst, ptrdiff_t stride_src,
+                                  int16_t *sao_offset_val, int sao_left_class,
+                                  int width, int height);
+
 void ff_hevc_idct_4x4_dc_8_neon(int16_t *coeffs);
 void ff_hevc_idct_8x8_dc_8_neon(int16_t *coeffs);
 void ff_hevc_idct_16x16_dc_8_neon(int16_t *coeffs);
@@ -53,6 +58,8 @@ av_cold void ff_hevc_dsp_init_aarch64(HEVCDSPContext *c, const int bit_depth)
 {
     int cpu_flags = av_get_cpu_flags();
     if (have_neon(cpu_flags) && bit_depth == 8) {
+        c->sao_band_filter[0]          = ff_hevc_sao_band_filter_8x8_8_neon;
+
         c->add_residual[0]             = ff_hevc_add_residual_4x4_8_neon;
         c->add_residual[1]             = ff_hevc_add_residual_8x8_8_neon;
         c->add_residual[2]             = ff_hevc_add_residual_16x16_8_neon;
diff --git a/libavcodec/aarch64/hevcdsp_sao_neon.S b/libavcodec/aarch64/hevcdsp_sao_neon.S
new file mode 100644
index 0000000000..25b6c25117
--- /dev/null
+++ b/libavcodec/aarch64/hevcdsp_sao_neon.S
@@ -0,0 +1,87 @@
+/* -*-arm64-*-
+ * vim: syntax=arm64asm
+ *
+ * AArch64 NEON optimised SAO functions for HEVC decoding
+ *
+ * Copyright (c) 2020 Josh Dekker <josh at itanimul.li>
+ *
+ * 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"
+
+// void sao_band_filter(uint8_t *_dst, uint8_t *_src,
+//                      ptrdiff_t stride_dst, ptrdiff_t stride_src,
+//                      int16_t *sao_offset_val, int sao_left_class,
+//                      int width, int height)
+function ff_hevc_sao_band_filter_8x8_8_neon, export=1
+    sub sp, sp, #64
+    stp xzr, xzr, [sp]
+    stp xzr, xzr, [sp, #16]
+    stp xzr, xzr, [sp, #32]
+    stp xzr, xzr, [sp, #48]
+    mov w8, #4
+.setup:
+    ldrsh x9, [x4, x8, lsl #1] // x9 = sao_offset_val[k+1]
+    subs w8, w8, #1
+    add w10, w8, w5 // x10 = k + sao_left_class
+    and w10, w10, #0x1F
+    strh w9, [sp, x10, lsl #1]
+    bne .setup
+    ld1 {v16.16B-v19.16B}, [sp], #64
+    movi v20.8H, #1
+0:  // beginning of line
+    mov w8, w6
+8:
+    // Simple layout for accessing 16bit values
+    // with 8bit LUT.
+    //
+    //   00  01  02  03  04  05  06  07
+    // +----------------------------------->
+    // |xDE#xAD|xCA#xFE|xBE#xEF|xFE#xED|....
+    // +----------------------------------->
+    //    i-0     i-1     i-2     i-3
+    // dst[x] = av_clip_pixel(src[x] + offset_table[src[x] >> shift]);
+    ld1 {v2.8B}, [x1]
+    // load src[x]
+    ushll v0.8H, v2.8B, #0
+    // >> shift
+    ushr v2.8H, v0.8H, #3 // BIT_DEPTH - 3
+    // x2 (access lower short)
+    shl v1.8H, v2.8H, #1 // low (x2, accessing short)
+    // +1 access upper short
+    add v3.8H, v1.8H, v20.8H
+    // shift insert index to upper byte
+    sli v1.8H, v3.8H, #8
+    // table
+    tbx v2.16B, {v16.16B-v19.16B}, v1.16B
+    // src[x] + table
+    add v1.8H, v0.8H, v2.8H
+    // clip + narrow
+    sqxtun v4.8B, v1.8H
+    // store
+    st1 {v4.8B}, [x0]
+    // done 8 pixels
+    subs w8, w8, #8
+    bne 8b
+    // finished line
+    subs w7, w7, #1
+    add x0, x0, x2 // dst += stride_dst
+    add x1, x1, x3 // src += stride_src
+    bne 0b
+    ret
+endfunc
-- 
2.24.3 (Apple Git-128)