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_CORNER_DETECT_H_ 13 #define AOM_AOM_DSP_FLOW_ESTIMATION_CORNER_DETECT_H_ 14 15 #include <stdio.h> 16 #include <stdlib.h> 17 #include <stdbool.h> 18 #include <memory.h> 19 20 #include "aom_dsp/pyramid.h" 21 #include "aom_util/aom_pthread.h" 22 23 #ifdef __cplusplus 24 extern "C" { 25 #endif 26 27 #define MAX_CORNERS 4096 28 29 typedef struct corner_list { 30 #if CONFIG_MULTITHREAD 31 // Mutex which is used to prevent the corner list from being computed twice 32 // at the same time 33 // 34 // Semantics: 35 // * This mutex must be held whenever reading or writing the `valid` flag 36 // 37 // * This mutex must also be held while computing the image pyramid, 38 // to ensure that only one thread may do so at a time. 39 // 40 // * However, once you have read the valid flag and seen a true value, 41 // it is safe to drop the mutex and read from the remaining fields. 42 // This is because, once the image pyramid is computed, its contents 43 // will not be changed until the parent frame buffer is recycled, 44 // which will not happen until there are no more outstanding references 45 // to the frame buffer. 46 pthread_mutex_t mutex; 47 #endif // CONFIG_MULTITHREAD 48 // Flag indicating whether the corner list contains valid data 49 bool valid; 50 // Number of corners found 51 int num_corners; 52 // (x, y) coordinates of each corner 53 int corners[2 * MAX_CORNERS]; 54 } CornerList; 55 56 size_t av1_get_corner_list_size(void); 57 58 CornerList *av1_alloc_corner_list(void); 59 60 bool av1_compute_corner_list(const YV12_BUFFER_CONFIG *frame, int bit_depth, 61 int downsample_level, CornerList *corners); 62 63 #ifndef NDEBUG 64 // Check if a corner list has already been computed. 65 // This is mostly a debug helper - as it is necessary to hold corners->mutex 66 // while reading the valid flag, we cannot just write: 67 // assert(corners->valid); 68 // This function allows the check to be correctly written as: 69 // assert(aom_is_corner_list_valid(corners)); 70 bool aom_is_corner_list_valid(CornerList *corners); 71 #endif 72 73 void av1_invalidate_corner_list(CornerList *corners); 74 75 void av1_free_corner_list(CornerList *corners); 76 77 #ifdef __cplusplus 78 } 79 #endif 80 81 #endif // AOM_AOM_DSP_FLOW_ESTIMATION_CORNER_DETECT_H_ 82