diff --git a/av1/common/mv.h b/av1/common/mv.h
index 22a47f763..a02d59866 100644
--- a/av1/common/mv.h
+++ b/av1/common/mv.h
@@ -102,8 +102,8 @@ typedef struct {
 #define GM_ALPHA_PREC_DIFF (WARPEDMODEL_PREC_BITS - GM_ALPHA_PREC_BITS)
 #define GM_ALPHA_DECODE_FACTOR (1 << GM_ALPHA_PREC_DIFF)
 
-#define GM_ABS_ALPHA_BITS 18
-#define GM_ABS_TRANS_BITS 18
+#define GM_ABS_ALPHA_BITS 8
+#define GM_ABS_TRANS_BITS 8
 
 #define GM_TRANS_MAX (1 << GM_ABS_TRANS_BITS)
 #define GM_ALPHA_MAX (1 << GM_ABS_ALPHA_BITS)
diff --git a/av1/common/warped_motion.c b/av1/common/warped_motion.c
index 146a14d8e..2e550cb0d 100644
--- a/av1/common/warped_motion.c
+++ b/av1/common/warped_motion.c
@@ -95,11 +95,11 @@ void projectPointsAffine(int16_t *mat, int *points, int *proj, const int n,
                                             WARPEDDIFF_PREC_BITS);
     if (subsampling_y)
       *(proj++) = ROUND_POWER_OF_TWO_SIGNED(
-          mat[5] * 2 * x + mat[4] * 2 * y + mat[0] +
-              (mat[5] + mat[4] - (1 << WARPEDMODEL_PREC_BITS)) / 2,
+          mat[4] * 2 * x + mat[5] * 2 * y + mat[0] +
+              (mat[4] + mat[5] - (1 << WARPEDMODEL_PREC_BITS)) / 2,
           WARPEDDIFF_PREC_BITS + 1);
     else
-      *(proj++) = ROUND_POWER_OF_TWO_SIGNED(mat[5] * x + mat[4] * y + mat[0],
+      *(proj++) = ROUND_POWER_OF_TWO_SIGNED(mat[4] * x + mat[5] * y + mat[0],
                                             WARPEDDIFF_PREC_BITS);
     points += stride_points - 2;
     proj += stride_proj - 2;
diff --git a/av1/decoder/decodeframe.c b/av1/decoder/decodeframe.c
index 6e52c79d9..031ddbc72 100644
--- a/av1/decoder/decodeframe.c
+++ b/av1/decoder/decodeframe.c
@@ -3411,12 +3411,12 @@ static void read_global_motion_params(Global_Motion_Params *params,
     case GLOBAL_ZERO: break;
     case GLOBAL_AFFINE:
       params->motion_params.wmmat[2].as_mv.row =
+          (aom_read_primitive_symmetric(r, GM_ABS_ALPHA_BITS) *
+           GM_ALPHA_DECODE_FACTOR);
+      params->motion_params.wmmat[2].as_mv.col =
           aom_read_primitive_symmetric(r, GM_ABS_ALPHA_BITS) *
               GM_ALPHA_DECODE_FACTOR +
           (1 << WARPEDMODEL_PREC_BITS);
-      params->motion_params.wmmat[2].as_mv.col =
-          (aom_read_primitive_symmetric(r, GM_ABS_ALPHA_BITS) *
-           GM_ALPHA_DECODE_FACTOR);
     // fallthrough intended
     case GLOBAL_ROTZOOM:
       params->motion_params.wmmat[1].as_mv.row =
diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index 49f1b44c3..6578c0cff 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -3213,11 +3213,11 @@ static void write_global_motion_params(Global_Motion_Params *params,
     case GLOBAL_ZERO: break;
     case GLOBAL_AFFINE:
       aom_write_primitive_symmetric(
-          w, (params->motion_params.wmmat[2].as_mv.row >> GM_ALPHA_PREC_DIFF) -
-                 (1 << GM_ALPHA_PREC_BITS),
+          w, (params->motion_params.wmmat[2].as_mv.row >> GM_ALPHA_PREC_DIFF),
           GM_ABS_ALPHA_BITS);
       aom_write_primitive_symmetric(
-          w, (params->motion_params.wmmat[2].as_mv.col >> GM_ALPHA_PREC_DIFF),
+          w, (params->motion_params.wmmat[2].as_mv.col >> GM_ALPHA_PREC_DIFF) -
+                 (1 << GM_ALPHA_PREC_BITS),
           GM_ABS_ALPHA_BITS);
     // fallthrough intended
     case GLOBAL_ROTZOOM:
diff --git a/av1/encoder/encodeframe.c b/av1/encoder/encodeframe.c
index 8796ac9c2..4b93ab65b 100644
--- a/av1/encoder/encodeframe.c
+++ b/av1/encoder/encodeframe.c
@@ -4479,7 +4479,7 @@ static void refine_integerized_param(WarpedMotionParams *wm,
 
 static void convert_to_params(double *H, TransformationType type,
                               int16_t *model) {
-  int i;
+  int i, diag_value;
   int alpha_present = 0;
   int n_params = n_trans_model_params[type];
   model[0] = (int16_t)floor(H[0] * (1 << GM_TRANS_PREC_BITS) + 0.5);
@@ -4489,11 +4489,13 @@ static void convert_to_params(double *H, TransformationType type,
   model[1] = (int16_t)clamp(model[1], GM_TRANS_MIN, GM_TRANS_MAX) *
              GM_TRANS_DECODE_FACTOR;
 
-  // TODO(sarahparker) 1 should be subtracted here
   for (i = 2; i < n_params; ++i) {
+    diag_value = ((i && 1) ? (1 << GM_ALPHA_PREC_BITS) : 0);
     model[i] = (int16_t)floor(H[i] * (1 << GM_ALPHA_PREC_BITS) + 0.5);
-    model[i] = (int16_t)clamp(model[i], GM_ALPHA_MIN, GM_ALPHA_MAX) *
-               GM_ALPHA_DECODE_FACTOR;
+    model[i] =
+        (int16_t)(clamp(model[i] - diag_value, GM_ALPHA_MIN, GM_ALPHA_MAX) +
+                  diag_value) *
+        GM_ALPHA_DECODE_FACTOR;
     alpha_present |= (model[i] != 0);
   }
 
diff --git a/av1/encoder/global_motion.h b/av1/encoder/global_motion.h
index aad8cc4f0..fa4f79117 100644
--- a/av1/encoder/global_motion.h
+++ b/av1/encoder/global_motion.h
@@ -17,7 +17,17 @@
 extern "C" {
 #endif
 
-// compute global motion parameters between two frames
+/*
+  Computes global motion parameters between two frames. The array
+  "params" should be length 9, where the first 2 slots are translation
+  parameters in (row, col) order, and the remaining slots correspond
+  to values in the transformation matrix of the corresponding motion
+  model. They are arranged in "params" such that values on the tx-matrix
+  diagonal have odd numbered indices so the folowing matrix:
+  A | B
+  C | D
+  would produce params = [trans row, trans col, B, A, C, D]
+*/
 int compute_global_motion_feature_based(TransformationType type,
                                         YV12_BUFFER_CONFIG *frm,
                                         YV12_BUFFER_CONFIG *ref,
diff --git a/av1/encoder/ransac.c b/av1/encoder/ransac.c
index a3072bc02..81c1c21eb 100644
--- a/av1/encoder/ransac.c
+++ b/av1/encoder/ransac.c
@@ -615,8 +615,8 @@ static void denormalizeAffine(double *H, double *T1, double *T2) {
   H[1] = Ha[2];
   H[2] = Ha[1];
   H[3] = Ha[0];
-  H[4] = Ha[4];
-  H[5] = Ha[3];
+  H[4] = Ha[3];
+  H[5] = Ha[4];
 }
 
 static void denormalizeRotZoom(double *H, double *T1, double *T2) {