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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.
*/
#ifndef AOM_AOM_DSP_FLOW_ESTIMATION_CORNER_DETECT_H_
#define AOM_AOM_DSP_FLOW_ESTIMATION_CORNER_DETECT_H_
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <memory.h>
#include "aom_dsp/pyramid.h"
#include "aom_util/aom_thread.h"
#ifdef __cplusplus
extern "C" {
#endif
#define MAX_CORNERS 4096
typedef struct corner_list {
#if CONFIG_MULTITHREAD
// Mutex which is used to prevent the corner list from being computed twice
// at the same time
//
// Semantics:
// * This mutex must be held whenever reading or writing the `valid` flag
//
// * This mutex must also be held while computing the image pyramid,
// to ensure that only one thread may do so at a time.
//
// * However, once you have read the valid flag and seen a true value,
// it is safe to drop the mutex and read from the remaining fields.
// This is because, once the image pyramid is computed, its contents
// will not be changed until the parent frame buffer is recycled,
// which will not happen until there are no more outstanding references
// to the frame buffer.
pthread_mutex_t mutex;
#endif // CONFIG_MULTITHREAD
// Flag indicating whether the corner list contains valid data
bool valid;
// Number of corners found
int num_corners;
// (x, y) coordinates of each corner
int corners[2 * MAX_CORNERS];
} CornerList;
size_t av1_get_corner_list_size(void);
CornerList *av1_alloc_corner_list(void);
bool av1_compute_corner_list(const ImagePyramid *pyr, CornerList *corners);
#ifndef NDEBUG
// Check if a corner list has already been computed.
// This is mostly a debug helper - as it is necessary to hold corners->mutex
// while reading the valid flag, we cannot just write:
// assert(corners->valid);
// This function allows the check to be correctly written as:
// assert(aom_is_corner_list_valid(corners));
bool aom_is_corner_list_valid(CornerList *corners);
#endif
void av1_invalidate_corner_list(CornerList *corners);
void av1_free_corner_list(CornerList *corners);
#ifdef __cplusplus
}
#endif
#endif // AOM_AOM_DSP_FLOW_ESTIMATION_CORNER_DETECT_H_
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