/* | |

* Copyright (c) 2021, Alliance for Open Media. All rights reserved | |

* | |

* This source code is subject to the terms of the BSD 3-Clause Clear License | |

* and the Alliance for Open Media Patent License 1.0. If the BSD 3-Clause Clear | |

* License was not distributed with this source code in the LICENSE file, you | |

* can obtain it at aomedia.org/license/software-license/bsd-3-c-c/. 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 | |

* aomedia.org/license/patent-license/. | |

*/ | |

#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); | |

} |