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+/*
+ * Copyright (c) 2024, Alliance for Open Media. All rights reserved
+ *
+ * This source code is subject to the terms of the BSD 2 Clause License and
+ * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
+ * was not distributed with this source code in the LICENSE file, you can
+ * obtain it at www.aomedia.org/license/software. If the Alliance for Open
+ * Media Patent License 1.0 was not distributed with this source code in the
+ * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
+ */
+
+#ifndef AOM_AOM_DSP_FLOW_ESTIMATION_ARM_DISFLOW_NEON_H_
+#define AOM_AOM_DSP_FLOW_ESTIMATION_ARM_DISFLOW_NEON_H_
+
+#include "aom_dsp/flow_estimation/disflow.h"
+
+#include <arm_neon.h>
+#include <math.h>
+
+#include "aom_dsp/arm/mem_neon.h"
+#include "config/aom_config.h"
+#include "config/aom_dsp_rtcd.h"
+
+static INLINE void get_cubic_kernel_dbl(double x, double kernel[4]) {
+ // Check that the fractional position is in range.
+ //
+ // Note: x is calculated from, e.g., `u_frac = u - floor(u)`.
+ // Mathematically, this implies that 0 <= x < 1. However, in practice it is
+ // possible to have x == 1 due to floating point rounding. This is fine,
+ // and we still interpolate correctly if we allow x = 1.
+ assert(0 <= x && x <= 1);
+
+ double x2 = x * x;
+ double x3 = x2 * x;
+ kernel[0] = -0.5 * x + x2 - 0.5 * x3;
+ kernel[1] = 1.0 - 2.5 * x2 + 1.5 * x3;
+ kernel[2] = 0.5 * x + 2.0 * x2 - 1.5 * x3;
+ kernel[3] = -0.5 * x2 + 0.5 * x3;
+}
+
+static INLINE void get_cubic_kernel_int(double x, int kernel[4]) {
+ double kernel_dbl[4];
+ get_cubic_kernel_dbl(x, kernel_dbl);
+
+ kernel[0] = (int)rint(kernel_dbl[0] * (1 << DISFLOW_INTERP_BITS));
+ kernel[1] = (int)rint(kernel_dbl[1] * (1 << DISFLOW_INTERP_BITS));
+ kernel[2] = (int)rint(kernel_dbl[2] * (1 << DISFLOW_INTERP_BITS));
+ kernel[3] = (int)rint(kernel_dbl[3] * (1 << DISFLOW_INTERP_BITS));
+}
+
+static INLINE void sobel_filter_x(const uint8_t *src, int src_stride,
+ int16_t *dst, int dst_stride) {
+ int16_t tmp[DISFLOW_PATCH_SIZE * (DISFLOW_PATCH_SIZE + 2)];
+
+ // Horizontal filter, using kernel {1, 0, -1}.
+ const uint8_t *src_start = src - 1 * src_stride - 1;
+
+ for (int i = 0; i < DISFLOW_PATCH_SIZE + 2; i++) {
+ uint8x16_t s = vld1q_u8(src_start + i * src_stride);
+ uint8x8_t s0 = vget_low_u8(s);
+ uint8x8_t s2 = vget_low_u8(vextq_u8(s, s, 2));
+
+ // Given that the kernel is {1, 0, -1} the convolution is a simple
+ // subtraction.
+ int16x8_t diff = vreinterpretq_s16_u16(vsubl_u8(s0, s2));
+
+ vst1q_s16(tmp + i * DISFLOW_PATCH_SIZE, diff);
+ }
+
+ // Vertical filter, using kernel {1, 2, 1}.
+ // This kernel can be split into two 2-taps kernels of value {1, 1}.
+ // That way we need only 3 add operations to perform the convolution, one of
+ // which can be reused for the next line.
+ int16x8_t s0 = vld1q_s16(tmp);
+ int16x8_t s1 = vld1q_s16(tmp + DISFLOW_PATCH_SIZE);
+ int16x8_t sum01 = vaddq_s16(s0, s1);
+ for (int i = 0; i < DISFLOW_PATCH_SIZE; i++) {
+ int16x8_t s2 = vld1q_s16(tmp + (i + 2) * DISFLOW_PATCH_SIZE);
+
+ int16x8_t sum12 = vaddq_s16(s1, s2);
+ int16x8_t sum = vaddq_s16(sum01, sum12);
+
+ vst1q_s16(dst + i * dst_stride, sum);
+
+ sum01 = sum12;
+ s1 = s2;
+ }
+}
+
+static INLINE void sobel_filter_y(const uint8_t *src, int src_stride,
+ int16_t *dst, int dst_stride) {
+ int16_t tmp[DISFLOW_PATCH_SIZE * (DISFLOW_PATCH_SIZE + 2)];
+
+ // Horizontal filter, using kernel {1, 2, 1}.
+ // This kernel can be split into two 2-taps kernels of value {1, 1}.
+ // That way we need only 3 add operations to perform the convolution.
+ const uint8_t *src_start = src - 1 * src_stride - 1;
+
+ for (int i = 0; i < DISFLOW_PATCH_SIZE + 2; i++) {
+ uint8x16_t s = vld1q_u8(src_start + i * src_stride);
+ uint8x8_t s0 = vget_low_u8(s);
+ uint8x8_t s1 = vget_low_u8(vextq_u8(s, s, 1));
+ uint8x8_t s2 = vget_low_u8(vextq_u8(s, s, 2));
+
+ uint16x8_t sum01 = vaddl_u8(s0, s1);
+ uint16x8_t sum12 = vaddl_u8(s1, s2);
+ uint16x8_t sum = vaddq_u16(sum01, sum12);
+
+ vst1q_s16(tmp + i * DISFLOW_PATCH_SIZE, vreinterpretq_s16_u16(sum));
+ }
+
+ // Vertical filter, using kernel {1, 0, -1}.
+ // Load the whole block at once to avoid redundant loads during convolution.
+ int16x8_t t[10];
+ load_s16_8x10(tmp, DISFLOW_PATCH_SIZE, &t[0], &t[1], &t[2], &t[3], &t[4],
+ &t[5], &t[6], &t[7], &t[8], &t[9]);
+
+ for (int i = 0; i < DISFLOW_PATCH_SIZE; i++) {
+ // Given that the kernel is {1, 0, -1} the convolution is a simple
+ // subtraction.
+ int16x8_t diff = vsubq_s16(t[i], t[i + 2]);
+
+ vst1q_s16(dst + i * dst_stride, diff);
+ }
+}
+
+#endif // AOM_AOM_DSP_FLOW_ESTIMATION_ARM_DISFLOW_NEON_H_