1 /* 2 * Copyright (c) 2016, Alliance for Open Media. All rights reserved. 3 * 4 * This source code is subject to the terms of the BSD 2 Clause License and 5 * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License 6 * was not distributed with this source code in the LICENSE file, you can 7 * obtain it at www.aomedia.org/license/software. If the Alliance for Open 8 * Media Patent License 1.0 was not distributed with this source code in the 9 * PATENTS file, you can obtain it at www.aomedia.org/license/patent. 10 */ 11 12 #ifndef AOM_AOM_DSP_FLOW_ESTIMATION_DISFLOW_H_ 13 #define AOM_AOM_DSP_FLOW_ESTIMATION_DISFLOW_H_ 14 15 #include <stdbool.h> 16 17 #include "aom_dsp/flow_estimation/flow_estimation.h" 18 #include "aom_scale/yv12config.h" 19 20 #ifdef __cplusplus 21 extern "C" { 22 #endif 23 24 // Number of pyramid levels in disflow computation 25 #define DISFLOW_PYRAMID_LEVELS 12 26 27 // Size of square patches in the disflow dense grid 28 // Must be a power of 2 29 #define DISFLOW_PATCH_SIZE_LOG2 3 30 #define DISFLOW_PATCH_SIZE (1 << DISFLOW_PATCH_SIZE_LOG2) 31 // Center point of square patch 32 #define DISFLOW_PATCH_CENTER ((DISFLOW_PATCH_SIZE / 2) - 1) 33 34 // Overall scale of the `dx`, `dy` and `dt` arrays in the disflow code 35 // In other words, the various derivatives are calculated with an internal 36 // precision of (8 + DISFLOW_DERIV_SCALE_LOG2) bits, from an 8-bit input. 37 // 38 // This must be carefully synchronized with the code in sobel_filter() 39 // (which fills the dx and dy arrays) and compute_flow_error() (which 40 // fills dt); see the comments in those functions for more details 41 #define DISFLOW_DERIV_SCALE_LOG2 3 42 #define DISFLOW_DERIV_SCALE (1 << DISFLOW_DERIV_SCALE_LOG2) 43 44 // Scale factor applied to each step in the main refinement loop 45 // 46 // This should be <= 1.0 to avoid overshoot. Values below 1.0 47 // may help in some cases, but slow convergence overall, so 48 // will require careful tuning. 49 // TODO(rachelbarker): Tune this value 50 #define DISFLOW_STEP_SIZE 1.0 51 52 // Step size at which we should terminate iteration 53 // The idea here is that, if we take a step which is much smaller than 1px in 54 // size, then the values won't change much from iteration to iteration, so 55 // many future steps will also be small, and that won't have much effect 56 // on the ultimate result. So we can terminate early. 57 // 58 // To look at it another way, when we take a small step, that means that 59 // either we're near to convergence (so can stop), or we're stuck in a 60 // shallow valley and will take many iterations to get unstuck. 61 // 62 // Solving the latter properly requires fancier methods, such as "gradient 63 // descent with momentum". For now, we terminate to avoid wasting a ton of 64 // time on points which are either nearly-converged or stuck. 65 // 66 // Terminating at 1/8 px seems to give good results for global motion estimation 67 #define DISFLOW_STEP_SIZE_THRESOLD (1. / 8.) 68 69 // Max number of iterations if warp convergence is not found 70 #define DISFLOW_MAX_ITR 4 71 72 // Internal precision of cubic interpolation filters 73 // The limiting factor here is that: 74 // * Before integerizing, the maximum value of any kernel tap is 1.0 75 // * After integerizing, each tap must fit into an int16_t. 76 // Thus the largest multiplier we can get away with is 2^14 = 16384, 77 // as 2^15 = 32768 is too large to fit in an int16_t. 78 #define DISFLOW_INTERP_BITS 14 79 80 typedef struct { 81 // Start of allocation for u and v buffers 82 double *buf0; 83 84 // x and y directions of flow, per patch 85 double *u; 86 double *v; 87 88 // Sizes of the above arrays 89 int width; 90 int height; 91 int stride; 92 } FlowField; 93 94 bool av1_compute_global_motion_disflow( 95 TransformationType type, YV12_BUFFER_CONFIG *src, YV12_BUFFER_CONFIG *ref, 96 int bit_depth, int downsample_level, MotionModel *motion_models, 97 int num_motion_models, bool *mem_alloc_failed); 98 99 #ifdef __cplusplus 100 } 101 #endif 102 103 #endif // AOM_AOM_DSP_FLOW_ESTIMATION_DISFLOW_H_ 104