Add function to compute matrices for DISflow system
This will eventually be used to form a system of equations
to compute the flow vectors for each patch.
Change-Id: I3415843f611a89648167a27ad9eba57e7e239bd3
diff --git a/av1/encoder/global_motion.c b/av1/encoder/global_motion.c
index 8b12ce4..e21d825 100644
--- a/av1/encoder/global_motion.c
+++ b/av1/encoder/global_motion.c
@@ -319,6 +319,33 @@
return 0;
}
#else
+// Computes the components of the system of equations used to solve for
+// a flow vector. This includes:
+// 1.) The hessian matrix for optical flow. This matrix is in the
+// form of:
+//
+// M = |sum(dx * dx) sum(dx * dy)|
+// |sum(dx * dy) sum(dy * dy)|
+//
+// 2.) b = |sum(dx * dt)|
+// |sum(dy * dt)|
+// Where the sums are computed over a square window of PATCH_SIZE.
+static INLINE void compute_flow_system(const double *dx, const double *dy,
+ const double *dt, int stride, double *M,
+ double *b) {
+ for (int i = 0; i < PATCH_SIZE; i++) {
+ for (int j = 0; j < PATCH_SIZE; j++) {
+ M[0] += dx[i * stride + j] * dx[i * stride + j];
+ M[1] += dx[i * stride + j] * dy[i * stride + j];
+ M[3] += dy[i * stride + j] * dy[i * stride + j];
+
+ b[0] += dx[i * stride + j] * dt[i * stride + j];
+ b[1] += dy[i * stride + j] * dt[i * stride + j];
+ }
+ }
+ M[2] = M[1];
+}
+
// Compute an image gradient using a sobel filter.
// If dir == 1, compute the x gradient. If dir == 0, compute y. This function
// assumes the images have been padded so that they can be processed in units
