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/*

 * Copyright (c) 2022, 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_PYRAMID_H_

#define AOM_AOM_DSP_PYRAMID_H_

#include <stddef.h>

#include <stdint.h>

#include <stdbool.h>

#include "config/aom_config.h"

#include "aom_scale/yv12config.h"

#include "aom_util/aom_pthread.h"

#ifdef __cplusplus

extern "C" {

#endif

// Minimum dimensions of a downsampled image

#define MIN_PYRAMID_SIZE_LOG2 3

#define MIN_PYRAMID_SIZE (1 << MIN_PYRAMID_SIZE_LOG2)

// Size of border around each pyramid image, in pixels

// Similarly to the border around regular image buffers, this border is filled

// with copies of the outermost pixels of the frame, to allow for more efficient

// convolution code

// TODO(rachelbarker): How many pixels do we actually need here?

// I think we only need 9 for disflow, but how many for corner matching?

#define PYRAMID_PADDING 16

// Byte alignment of each line within the image pyramids.

// That is, the first pixel inside the image (ie, not in the border region),

// on each row of each pyramid level, is aligned to this byte alignment.

// This value must be a power of 2.

#define PYRAMID_ALIGNMENT 32

typedef struct {

  uint8_t *buffer;

  int width;

  int height;

  int stride;

} PyramidLayer;

// Struct for an image pyramid

typedef struct image_pyramid {

#if CONFIG_MULTITHREAD

  // Mutex which is used to prevent the pyramid being computed twice at the

  // same time

//

  // Semantics:

  // * This mutex must be held whenever reading or writing the

  //   `filled_levels` field

//

  // * 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 filled_levels field and observed

  //   a value N, it is safe to drop the mutex and read from the remaining

  //   fields, including the first N pyramid levels (but no higher).

  //   Note that filled_levels must be read once and cached in a local variable

  //   in order for this to be safe - it cannot be re-read without retaking

  //   the mutex.

//

  //   This works 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

  // Maximum number of levels for the given frame size

  // We always allocate enough memory for this many levels, as the memory

  // cost of higher levels of the pyramid is minimal.

  int max_levels;

  // Number of levels which currently hold valid data

  int filled_levels;

  // Pointer to allocated buffer

  uint8_t *buffer_alloc;

  // Data for each level

  // The `buffer` pointers inside this array point into the region which

  // is stored in the `buffer_alloc` field here

  PyramidLayer *layers;

} ImagePyramid;

size_t aom_get_pyramid_alloc_size(int width, int height, bool image_is_16bit);

ImagePyramid *aom_alloc_pyramid(int width, int height, bool image_is_16bit);

// Fill out a downsampling pyramid for a given frame.

//

// The top level (index 0) will always be an 8-bit copy of the input frame,

// regardless of the input bit depth. Additional levels are then downscaled

// by powers of 2.

//

// This function will ensure that the first `n_levels` levels of the pyramid

// are filled, unless the frame is too small to have this many levels.

// In that case, we will fill all available levels and then stop.

//

// Returns the actual number of levels filled, capped at n_levels,

// or -1 on error.

int aom_compute_pyramid(const YV12_BUFFER_CONFIG *frame, int bit_depth,

                        int n_levels, ImagePyramid *pyr);

#ifndef NDEBUG

// Check if a pyramid has already been computed to at least n levels

// This is mostly a debug helper - as it is necessary to hold pyr->mutex

// while reading the number of already-computed levels, we cannot just write:

//   assert(pyr->filled_levels >= n_levels);

// This function allows the check to be correctly written as:

//   assert(aom_is_pyramid_valid(pyr, n_levels));

//

// Note: This deliberately does not restrict n_levels based on the maximum

// number of permitted levels for the frame size. This allows the check to

// catch cases where the caller forgets to handle the case where

// max_levels is less than the requested number of levels

bool aom_is_pyramid_valid(ImagePyramid *pyr, int n_levels);

#endif

// Mark a pyramid as no longer containing valid data.

// This must be done whenever the corresponding frame buffer is reused

void aom_invalidate_pyramid(ImagePyramid *pyr);

// Release the memory associated with a pyramid

void aom_free_pyramid(ImagePyramid *pyr);

#ifdef __cplusplus

#endif

#endif  // AOM_AOM_DSP_PYRAMID_H_