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Comment and clean up hexagon search.

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This commit is contained in:
Ari Koivula 2013-10-22 11:40:24 +03:00
parent c0f06fdb9e
commit a81cc45b97
1 changed files with 41 additions and 12 deletions
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53
src/search.c
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@ -67,6 +67,27 @@ const vector2d small_hexbs[5] = {
{ -1, -1 }, { -1, 0 }, { 1, 0 }, { 1, 1 }
};
/**
* \brief Do motion search using the HEXBS algorithm.
*
* \param depth log2 depth of the search
* \param pic Picture motion vector is searched for.
* \param ref Picture motion vector is searched from.
* \param orig Top left corner of the searched for block.
* \param mv_in_out Predicted mv in and best out. Quarter pixel precision.
*
* \returns Cost of the motion vector.
*
* Motion vector is searched by first searching iteratively with the large
* hexagon pattern until the best match is at the center of the hexagon.
* As a final step a smaller hexagon is used to check the adjacent pixels.
*
* If a non 0,0 predicted motion vector predictor is given as mv_in_out,
* the 0,0 vector is also tried. This is hoped to help in the case where
* the predicted motion vector is way off. In the future even more additional
* points like 0,0 might be used, such as vectors from top or left.
*/
unsigned hexagon_search(unsigned depth,
const picture *pic, const picture *ref,
const vector2d *orig, vector2d *mv_in_out)
@ -79,11 +100,11 @@ unsigned hexagon_search(unsigned depth,
// Search the initial 7 points of the hexagon.
for (i = 0; i < 7; ++i) {
const vector2d *pattern = large_hexbs + i;
const vector2d *pattern = &large_hexbs[i];
unsigned cost = calc_sad(pic, ref, orig->x, orig->y,
orig->x + mv.x + pattern->x, orig->y + mv.y + pattern->y,
block_width, block_width);
if (cost > 0 && cost < best_cost) {
if (cost < best_cost) {
best_cost = cost;
best_index = i;
}
@ -94,19 +115,21 @@ unsigned hexagon_search(unsigned depth,
unsigned cost = calc_sad(pic, ref, orig->x, orig->y,
orig->x, orig->y,
block_width, block_width);
if (cost > 0 && cost < best_cost) {
// If the 0,0 is better, redo the hexagon around that point.
if (cost < best_cost) {
best_cost = cost;
best_index = 0;
mv.x = 0;
mv.y = 0;
// Redo the search around the 0,0 point.
for (i = 1; i < 7; ++i) {
const vector2d *pattern = large_hexbs + i;
const vector2d *pattern = &large_hexbs[i];
unsigned cost = calc_sad(pic, ref, orig->x, orig->y,
orig->x + pattern->x, orig->y + pattern->y,
orig->x + pattern->x,
orig->y + pattern->y,
block_width, block_width);
if (cost > 0 && cost < best_cost) {
if (cost < best_cost) {
best_cost = cost;
best_index = i;
}
@ -133,12 +156,12 @@ unsigned hexagon_search(unsigned depth,
// Iterate through the next 3 points.
for (i = 0; i < 3; ++i) {
const vector2d *offset = large_hexbs + start + i;
const vector2d *offset = &large_hexbs[start + i];
unsigned cost = calc_sad(pic, ref, orig->x, orig->y,
orig->x + mv.x + offset->x,
orig->y + mv.y + offset->y,
block_width, block_width);
if (cost > 0 && cost < best_cost) {
if (cost < best_cost) {
best_cost = cost;
best_index = start + i;
}
@ -146,14 +169,17 @@ unsigned hexagon_search(unsigned depth,
}
}
// Do the final step of the search with a small pattern.
// Move the center to the best match.
mv.x += large_hexbs[best_index].x;
mv.y += large_hexbs[best_index].y;
best_index = 0;
// Do the final step of the search with a small pattern.
for (i = 1; i < 5; ++i) {
const vector2d *offset = small_hexbs + i;
const vector2d *offset = &small_hexbs[i];
unsigned cost = calc_sad(pic, ref, orig->x, orig->y,
orig->x + mv.x + offset->x, orig->y + mv.y + offset->y,
orig->x + mv.x + offset->x,
orig->y + mv.y + offset->y,
block_width, block_width);
if (cost > 0 && cost < best_cost) {
best_cost = cost;
@ -161,8 +187,11 @@ unsigned hexagon_search(unsigned depth,
}
}
// Adjust the movement vector according to the final best match.
mv.x += small_hexbs[best_index].x;
mv.y += small_hexbs[best_index].y;
// Return final movement vector in quarter-pixel precision.
mv_in_out->x = mv.x << 2;
mv_in_out->y = mv.y << 2;