From 15338d5f40b3361ce82840573f65dc42ce899fba Mon Sep 17 00:00:00 2001
From: David Barker <david.barker@argondesign.com>
Date: Mon, 13 Feb 2017 15:30:59 +0000
Subject: [PATCH] Speed up global motion determination
When global-motion is enabled, a considerable amount
of encoder time is spent in the functions in corner_match.c.
This patch optimizes those functions to be 3.5-4x as fast,
leading to an end-to-end encoder speed improvement
(on 20 frames of tempete_cif.y4m) of:
200kbps: ~26% faster
800kbps: ~19% faster
2800kbps: ~12% faster
Change-Id: I04d3f87484c36c41eb5a1e86e814f2accbe86297
---
av1/encoder/corner_match.c | 140 ++++++++++++++++--------------------
av1/encoder/corner_match.h | 6 +-
av1/encoder/global_motion.c | 6 +-
av1/encoder/ransac.c | 16 ++---
av1/encoder/ransac.h | 16 ++---
5 files changed, 81 insertions(+), 103 deletions(-)
diff --git a/av1/encoder/corner_match.c b/av1/encoder/corner_match.c
index 63225a8b32..64ee0c5ae1 100644
--- a/av1/encoder/corner_match.c
+++ b/av1/encoder/corner_match.c
@@ -24,11 +24,13 @@
#define THRESHOLD_NCC 0.75
-static double compute_variance(unsigned char *im, int stride, int x, int y,
- double *mean) {
- double sum = 0.0;
- double sumsq = 0.0;
- double var;
+/* Compute var(im) * MATCH_SZ_SQ over a MATCH_SZ by MATCH_SZ window of im,
+ centered at (x, y).
+*/
+static double compute_variance(unsigned char *im, int stride, int x, int y) {
+ int sum = 0.0;
+ int sumsq = 0.0;
+ int var;
int i, j;
for (i = 0; i < MATCH_SZ; ++i)
for (j = 0; j < MATCH_SZ; ++j) {
@@ -36,39 +38,45 @@ static double compute_variance(unsigned char *im, int stride, int x, int y,
sumsq += im[(i + y - MATCH_SZ_BY2) * stride + (j + x - MATCH_SZ_BY2)] *
im[(i + y - MATCH_SZ_BY2) * stride + (j + x - MATCH_SZ_BY2)];
}
- var = (sumsq * MATCH_SZ_SQ - sum * sum) / (MATCH_SZ_SQ * MATCH_SZ_SQ);
- if (mean) *mean = sum / MATCH_SZ_SQ;
- return var;
+ var = sumsq * MATCH_SZ_SQ - sum * sum;
+ return (double)var;
}
+/* Compute corr(im1, im2) * MATCH_SZ * stddev(im1), where the
+ correlation/standard deviation are taken over MATCH_SZ by MATCH_SZ windows
+ of each image, centered at (x1, y1) and (x2, y2) respectively.
+*/
static double compute_cross_correlation(unsigned char *im1, int stride1, int x1,
int y1, unsigned char *im2, int stride2,
int x2, int y2) {
- double sum1 = 0;
- double sum2 = 0;
- double cross = 0;
- double corr;
+ int v1, v2;
+ int sum1 = 0;
+ int sum2 = 0;
+ int sumsq2 = 0;
+ int cross = 0;
+ int var2, cov;
int i, j;
for (i = 0; i < MATCH_SZ; ++i)
for (j = 0; j < MATCH_SZ; ++j) {
- sum1 += im1[(i + y1 - MATCH_SZ_BY2) * stride1 + (j + x1 - MATCH_SZ_BY2)];
- sum2 += im2[(i + y2 - MATCH_SZ_BY2) * stride2 + (j + x2 - MATCH_SZ_BY2)];
- cross +=
- im1[(i + y1 - MATCH_SZ_BY2) * stride1 + (j + x1 - MATCH_SZ_BY2)] *
- im2[(i + y2 - MATCH_SZ_BY2) * stride2 + (j + x2 - MATCH_SZ_BY2)];
+ v1 = im1[(i + y1 - MATCH_SZ_BY2) * stride1 + (j + x1 - MATCH_SZ_BY2)];
+ v2 = im2[(i + y2 - MATCH_SZ_BY2) * stride2 + (j + x2 - MATCH_SZ_BY2)];
+ sum1 += v1;
+ sum2 += v2;
+ sumsq2 += v2 * v2;
+ cross += v1 * v2;
}
- corr = (cross * MATCH_SZ_SQ - sum1 * sum2) / (MATCH_SZ_SQ * MATCH_SZ_SQ);
- return corr;
+ var2 = sumsq2 * MATCH_SZ_SQ - sum2 * sum2;
+ cov = cross * MATCH_SZ_SQ - sum1 * sum2;
+ return cov / sqrt((double)var2);
}
-static int is_eligible_point(double pointx, double pointy, int width,
- int height) {
+static int is_eligible_point(int pointx, int pointy, int width, int height) {
return (pointx >= MATCH_SZ_BY2 && pointy >= MATCH_SZ_BY2 &&
pointx + MATCH_SZ_BY2 < width && pointy + MATCH_SZ_BY2 < height);
}
-static int is_eligible_distance(double point1x, double point1y, double point2x,
- double point2y, int width, int height) {
+static int is_eligible_distance(int point1x, int point1y, int point2x,
+ int point2y, int width, int height) {
const int thresh = (width < height ? height : width) >> 4;
return ((point1x - point2x) * (point1x - point2x) +
(point1y - point2y) * (point1y - point2y)) <= thresh * thresh;
@@ -81,32 +89,21 @@ static void improve_correspondence(unsigned char *frm, unsigned char *ref,
int num_correspondences) {
int i;
for (i = 0; i < num_correspondences; ++i) {
- double template_norm =
- compute_variance(frm, frm_stride, (int)correspondences[i].x,
- (int)correspondences[i].y, NULL);
int x, y, best_x = 0, best_y = 0;
double best_match_ncc = 0.0;
for (y = -SEARCH_SZ_BY2; y <= SEARCH_SZ_BY2; ++y) {
for (x = -SEARCH_SZ_BY2; x <= SEARCH_SZ_BY2; ++x) {
double match_ncc;
- double subimage_norm;
- if (!is_eligible_point((int)correspondences[i].rx + x,
- (int)correspondences[i].ry + y, width, height))
+ if (!is_eligible_point(correspondences[i].rx + x,
+ correspondences[i].ry + y, width, height))
continue;
- if (!is_eligible_distance(
- (int)correspondences[i].x, (int)correspondences[i].y,
- (int)correspondences[i].rx + x, (int)correspondences[i].ry + y,
- width, height))
+ if (!is_eligible_distance(correspondences[i].x, correspondences[i].y,
+ correspondences[i].rx + x,
+ correspondences[i].ry + y, width, height))
continue;
- subimage_norm =
- compute_variance(ref, ref_stride, (int)correspondences[i].rx + x,
- (int)correspondences[i].ry + y, NULL);
match_ncc = compute_cross_correlation(
- frm, frm_stride, (int)correspondences[i].x,
- (int)correspondences[i].y, ref, ref_stride,
- (int)correspondences[i].rx + x,
- (int)correspondences[i].ry + y) /
- sqrt(template_norm * subimage_norm);
+ frm, frm_stride, correspondences[i].x, correspondences[i].y, ref,
+ ref_stride, correspondences[i].rx + x, correspondences[i].ry + y);
if (match_ncc > best_match_ncc) {
best_match_ncc = match_ncc;
best_y = y;
@@ -114,36 +111,25 @@ static void improve_correspondence(unsigned char *frm, unsigned char *ref,
}
}
}
- correspondences[i].rx += (double)best_x;
- correspondences[i].ry += (double)best_y;
+ correspondences[i].rx += best_x;
+ correspondences[i].ry += best_y;
}
for (i = 0; i < num_correspondences; ++i) {
- double template_norm =
- compute_variance(ref, ref_stride, (int)correspondences[i].rx,
- (int)correspondences[i].ry, NULL);
int x, y, best_x = 0, best_y = 0;
double best_match_ncc = 0.0;
for (y = -SEARCH_SZ_BY2; y <= SEARCH_SZ_BY2; ++y)
for (x = -SEARCH_SZ_BY2; x <= SEARCH_SZ_BY2; ++x) {
double match_ncc;
- double subimage_norm;
- if (!is_eligible_point((int)correspondences[i].x + x,
- (int)correspondences[i].y + y, width, height))
+ if (!is_eligible_point(correspondences[i].x + x,
+ correspondences[i].y + y, width, height))
continue;
- if (!is_eligible_distance((int)correspondences[i].x + x,
- (int)correspondences[i].y + y,
- (int)correspondences[i].rx,
- (int)correspondences[i].ry, width, height))
+ if (!is_eligible_distance(
+ correspondences[i].x + x, correspondences[i].y + y,
+ correspondences[i].rx, correspondences[i].ry, width, height))
continue;
- subimage_norm =
- compute_variance(frm, frm_stride, (int)correspondences[i].x + x,
- (int)correspondences[i].y + y, NULL);
- match_ncc =
- compute_cross_correlation(
- frm, frm_stride, (int)correspondences[i].x + x,
- (int)correspondences[i].y + y, ref, ref_stride,
- (int)correspondences[i].rx, (int)correspondences[i].ry) /
- sqrt(template_norm * subimage_norm);
+ match_ncc = compute_cross_correlation(
+ ref, ref_stride, correspondences[i].rx, correspondences[i].ry, frm,
+ frm_stride, correspondences[i].x + x, correspondences[i].y + y);
if (match_ncc > best_match_ncc) {
best_match_ncc = match_ncc;
best_y = y;
@@ -159,7 +145,7 @@ int determine_correspondence(unsigned char *frm, int *frm_corners,
int num_frm_corners, unsigned char *ref,
int *ref_corners, int num_ref_corners, int width,
int height, int frm_stride, int ref_stride,
- double *correspondence_pts) {
+ int *correspondence_pts) {
// TODO(sarahparker) Improve this to include 2-way match
int i, j;
Correspondence *correspondences = (Correspondence *)correspondence_pts;
@@ -171,11 +157,8 @@ int determine_correspondence(unsigned char *frm, int *frm_corners,
if (!is_eligible_point(frm_corners[2 * i], frm_corners[2 * i + 1], width,
height))
continue;
- template_norm = compute_variance(frm, frm_stride, frm_corners[2 * i],
- frm_corners[2 * i + 1], NULL);
for (j = 0; j < num_ref_corners; ++j) {
double match_ncc;
- double subimage_norm;
if (!is_eligible_point(ref_corners[2 * j], ref_corners[2 * j + 1], width,
height))
continue;
@@ -183,25 +166,24 @@ int determine_correspondence(unsigned char *frm, int *frm_corners,
ref_corners[2 * j], ref_corners[2 * j + 1],
width, height))
continue;
- subimage_norm = compute_variance(ref, ref_stride, ref_corners[2 * j],
- ref_corners[2 * j + 1], NULL);
- match_ncc = compute_cross_correlation(frm, frm_stride, frm_corners[2 * i],
- frm_corners[2 * i + 1], ref,
- ref_stride, ref_corners[2 * j],
- ref_corners[2 * j + 1]) /
- sqrt(template_norm * subimage_norm);
+ match_ncc = compute_cross_correlation(
+ frm, frm_stride, frm_corners[2 * i], frm_corners[2 * i + 1], ref,
+ ref_stride, ref_corners[2 * j], ref_corners[2 * j + 1]);
if (match_ncc > best_match_ncc) {
best_match_ncc = match_ncc;
best_match_j = j;
}
}
- if (best_match_ncc > THRESHOLD_NCC) {
- correspondences[num_correspondences].x = (double)frm_corners[2 * i];
- correspondences[num_correspondences].y = (double)frm_corners[2 * i + 1];
- correspondences[num_correspondences].rx =
- (double)ref_corners[2 * best_match_j];
+ // Note: We want to test if the best correlation is >= THRESHOLD_NCC,
+ // but need to account for the normalization in compute_cross_correlation.
+ template_norm = compute_variance(frm, frm_stride, frm_corners[2 * i],
+ frm_corners[2 * i + 1]);
+ if (best_match_ncc > THRESHOLD_NCC * sqrt(template_norm)) {
+ correspondences[num_correspondences].x = frm_corners[2 * i];
+ correspondences[num_correspondences].y = frm_corners[2 * i + 1];
+ correspondences[num_correspondences].rx = ref_corners[2 * best_match_j];
correspondences[num_correspondences].ry =
- (double)ref_corners[2 * best_match_j + 1];
+ ref_corners[2 * best_match_j + 1];
num_correspondences++;
}
}
diff --git a/av1/encoder/corner_match.h b/av1/encoder/corner_match.h
index 3618aa0c65..c0458642c1 100644
--- a/av1/encoder/corner_match.h
+++ b/av1/encoder/corner_match.h
@@ -16,14 +16,14 @@
#include <memory.h>
typedef struct {
- double x, y;
- double rx, ry;
+ int x, y;
+ int rx, ry;
} Correspondence;
int determine_correspondence(unsigned char *frm, int *frm_corners,
int num_frm_corners, unsigned char *ref,
int *ref_corners, int num_ref_corners, int width,
int height, int frm_stride, int ref_stride,
- double *correspondence_pts);
+ int *correspondence_pts);
#endif // AV1_ENCODER_CORNER_MATCH_H_
diff --git a/av1/encoder/global_motion.c b/av1/encoder/global_motion.c
index 526e897a76..8259c45426 100644
--- a/av1/encoder/global_motion.c
+++ b/av1/encoder/global_motion.c
@@ -218,7 +218,7 @@ static INLINE RansacFunc get_ransac_type(TransformationType type) {
// computes global motion parameters by fitting a model using RANSAC
static int compute_global_motion_params(TransformationType type,
- double *correspondences,
+ int *correspondences,
int num_correspondences, double *params,
int *inlier_map) {
int result;
@@ -259,7 +259,7 @@ int compute_global_motion_feature_based(TransformationType type,
double *params) {
int num_frm_corners, num_ref_corners;
int num_correspondences;
- double *correspondences;
+ int *correspondences;
int num_inliers;
int frm_corners[2 * MAX_CORNERS], ref_corners[2 * MAX_CORNERS];
int *inlier_map = NULL;
@@ -291,7 +291,7 @@ int compute_global_motion_feature_based(TransformationType type,
// find correspondences between the two images
correspondences =
- (double *)malloc(num_frm_corners * 4 * sizeof(*correspondences));
+ (int *)malloc(num_frm_corners * 4 * sizeof(*correspondences));
num_correspondences = determine_correspondence(
frm_buffer, (int *)frm_corners, num_frm_corners, ref_buffer,
(int *)ref_corners, num_ref_corners, frm->y_width, frm->y_height,
diff --git a/av1/encoder/ransac.c b/av1/encoder/ransac.c
index ff62105e7a..766a1cf513 100644
--- a/av1/encoder/ransac.c
+++ b/av1/encoder/ransac.c
@@ -116,7 +116,7 @@ static int get_rand_indices(int npoints, int minpts, int *indices,
return 1;
}
-static int ransac(double *matched_points, int npoints, int *number_of_inliers,
+static int ransac(int *matched_points, int npoints, int *number_of_inliers,
int *best_inlier_mask, double *best_params, const int minpts,
IsDegenerateFunc is_degenerate,
FindTransformationFunc find_transformation,
@@ -305,31 +305,29 @@ static int is_degenerate_homography(double *p) {
is_collinear3(p, p + 4, p + 6) || is_collinear3(p + 2, p + 4, p + 6);
}
-int ransac_translation(double *matched_points, int npoints,
- int *number_of_inliers, int *best_inlier_mask,
- double *best_params) {
+int ransac_translation(int *matched_points, int npoints, int *number_of_inliers,
+ int *best_inlier_mask, double *best_params) {
return ransac(matched_points, npoints, number_of_inliers, best_inlier_mask,
best_params, 3, is_degenerate_translation, find_translation,
project_points_double_translation);
}
-int ransac_rotzoom(double *matched_points, int npoints, int *number_of_inliers,
+int ransac_rotzoom(int *matched_points, int npoints, int *number_of_inliers,
int *best_inlier_mask, double *best_params) {
return ransac(matched_points, npoints, number_of_inliers, best_inlier_mask,
best_params, 3, is_degenerate_affine, find_rotzoom,
project_points_double_rotzoom);
}
-int ransac_affine(double *matched_points, int npoints, int *number_of_inliers,
+int ransac_affine(int *matched_points, int npoints, int *number_of_inliers,
int *best_inlier_mask, double *best_params) {
return ransac(matched_points, npoints, number_of_inliers, best_inlier_mask,
best_params, 3, is_degenerate_affine, find_affine,
project_points_double_affine);
}
-int ransac_homography(double *matched_points, int npoints,
- int *number_of_inliers, int *best_inlier_mask,
- double *best_params) {
+int ransac_homography(int *matched_points, int npoints, int *number_of_inliers,
+ int *best_inlier_mask, double *best_params) {
return ransac(matched_points, npoints, number_of_inliers, best_inlier_mask,
best_params, 4, is_degenerate_homography, find_homography,
project_points_double_homography);
diff --git a/av1/encoder/ransac.h b/av1/encoder/ransac.h
index 3a749b2cc6..c45603ca75 100644
--- a/av1/encoder/ransac.h
+++ b/av1/encoder/ransac.h
@@ -19,20 +19,18 @@
#include "av1/common/warped_motion.h"
-typedef int (*RansacFunc)(double *matched_points, int npoints,
+typedef int (*RansacFunc)(int *matched_points, int npoints,
int *number_of_inliers, int *best_inlier_mask,
double *best_params);
/* Each of these functions fits a motion model from a set of
corresponding points in 2 frames using RANSAC.*/
-int ransac_homography(double *matched_points, int npoints,
- int *number_of_inliers, int *best_inlier_indices,
- double *best_params);
-int ransac_affine(double *matched_points, int npoints, int *number_of_inliers,
+int ransac_homography(int *matched_points, int npoints, int *number_of_inliers,
+ int *best_inlier_indices, double *best_params);
+int ransac_affine(int *matched_points, int npoints, int *number_of_inliers,
int *best_inlier_indices, double *best_params);
-int ransac_rotzoom(double *matched_points, int npoints, int *number_of_inliers,
+int ransac_rotzoom(int *matched_points, int npoints, int *number_of_inliers,
int *best_inlier_indices, double *best_params);
-int ransac_translation(double *matched_points, int npoints,
- int *number_of_inliers, int *best_inlier_indices,
- double *best_params);
+int ransac_translation(int *matched_points, int npoints, int *number_of_inliers,
+ int *best_inlier_indices, double *best_params);
#endif // AV1_ENCODER_RANSAC_H_
--
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