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/*
* Copyright (c) 2016, 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.
*/
#include <assert.h>
#include "aom/aom_integer.h"
#include "aom_ports/mem.h"
#include "aom_dsp/aom_dsp_common.h"
#include "av1/common/reconinter.h"
#define MAX_MASK_VALUE (1 << WEDGE_WEIGHT_BITS)
/**
* Computes SSE of a compound predictor constructed from 2 fundamental
* predictors p0 and p1 using blending with mask.
*
* r1: Residuals of p1.
* (source - p1)
* d: Difference of p1 and p0.
* (p1 - p0)
* m: The blending mask
* N: Number of pixels
*
* 'r1', 'd', and 'm' are contiguous.
*
* Computes:
* Sum((MAX_MASK_VALUE*r1 + mask*d)**2), which is equivalent to:
* Sum((mask*r0 + (MAX_MASK_VALUE-mask)*r1)**2),
* where r0 is (source - p0), and r1 is (source - p1), which is in turn
* is equivalent to:
* Sum((source*MAX_MASK_VALUE - (mask*p0 + (MAX_MASK_VALUE-mask)*p1))**2),
* which is the SSE of the residuals of the compound predictor scaled up by
* MAX_MASK_VALUE**2.
*
* Note that we clamp the partial term in the loop to 16 bits signed. This is
* to facilitate equivalent SIMD implementation. It should have no effect if
* residuals are within 16 - WEDGE_WEIGHT_BITS (=10) signed, which always
* holds for 8 bit input, and on real input, it should hold practically always,
* as residuals are expected to be small.
*/
uint64_t av1_wedge_sse_from_residuals_c(const int16_t *r1, const int16_t *d,
const uint8_t *m, int N) {
uint64_t csse = 0;
int i;
for (i = 0; i < N; i++) {
int32_t t = MAX_MASK_VALUE * r1[i] + m[i] * d[i];
t = clamp(t, INT16_MIN, INT16_MAX);
csse += t * t;
}
return ROUND_POWER_OF_TWO(csse, 2 * WEDGE_WEIGHT_BITS);
}
/**
* Choose the mask sign for a compound predictor.
*
* ds: Difference of the squares of the residuals.
* r0**2 - r1**2
* m: The blending mask
* N: Number of pixels
* limit: Pre-computed threshold value.
* MAX_MASK_VALUE/2 * (sum(r0**2) - sum(r1**2))
*
* 'ds' and 'm' are contiguous.
*
* Returns true if the negated mask has lower SSE compared to the positive
* mask. Computation is based on:
* Sum((mask*r0 + (MAX_MASK_VALUE-mask)*r1)**2)
* >
* Sum(((MAX_MASK_VALUE-mask)*r0 + mask*r1)**2)
*
* which can be simplified to:
*
* Sum(mask*(r0**2 - r1**2)) > MAX_MASK_VALUE/2 * (sum(r0**2) - sum(r1**2))
*
* The right hand side does not depend on the mask, and needs to be passed as
* the 'limit' parameter.
*
* After pre-computing (r0**2 - r1**2), which is passed in as 'ds', the left
* hand side is simply a scalar product between an int16_t and uint8_t vector.
*
* Note that for efficiency, ds is stored on 16 bits. Real input residuals
* being small, this should not cause a noticeable issue.
*/
int8_t av1_wedge_sign_from_residuals_c(const int16_t *ds, const uint8_t *m,
int N, int64_t limit) {
int64_t acc = 0;
do {
acc += *ds++ * *m++;
} while (--N);
return acc > limit;
}
/**
* Compute the element-wise difference of the squares of 2 arrays.
*
* d: Difference of the squares of the inputs: a**2 - b**2
* a: First input array
* b: Second input array
* N: Number of elements
*
* 'd', 'a', and 'b' are contiguous.
*
* The result is saturated to signed 16 bits.
*/
void av1_wedge_compute_delta_squares_c(int16_t *d, const int16_t *a,
const int16_t *b, int N) {
int i;
for (i = 0; i < N; i++)
d[i] = clamp(a[i] * a[i] - b[i] * b[i], INT16_MIN, INT16_MAX);
}