commit f6eaa159d74fc95b8cb28d7afa37ce0cb03aa9d3
author David Michael Barr <b@rr-dav.id.au> Wed Jul 19 19:42:28 2017 +0900
committer David Michael Barr <b@rr-dav.id.au> Sat Jul 29 00:44:42 2017 +0000
tree 9a18fbfb9b2a554f3f4d9df45d6b52de01b12781
parent 9136ab7ded3b404c64288da89152ecbe609be6b9

[CFL] Uniform Q3 alpha grid with extent [-2, 2]

Expand the range of alpha to [-2, 2] in Q3.
Jointly signal the signs, including zeros.
Use the signs to give context for each quadrant
and half-axis. The (0, 0) point is excluded.
Symmetry in alpha_u == alpha_v yields 6 contexts.

Results on Subset1 (Compared to 9136ab7d with CFL enabled)

   PSNR | PSNR Cb | PSNR Cr | PSNR HVS |    SSIM | MS SSIM | CIEDE 2000
-0.0792 | -0.7535 | -0.7574 |  -0.0639 | -0.0843 | -0.0665 |    -0.3324

Change-Id: I250369692e92a91d9c8d174a203d441217d15063
Signed-off-by: David Michael Barr <b@rr-dav.id.au>

av1/encoder/bitstream.c

diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index 43b2521..bd3591c 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -1642,23 +1642,18 @@
 }
 
 #if CONFIG_CFL
-static void write_cfl_alphas(FRAME_CONTEXT *const frame_ctx, int ind,
-                             const CFL_SIGN_TYPE signs[CFL_SIGNS],
-                             aom_writer *w) {
-  // Check for uninitialized signs
-  if (cfl_alpha_codes[ind][CFL_PRED_U] == 0)
-    assert(signs[CFL_PRED_U] == CFL_SIGN_POS);
-  if (cfl_alpha_codes[ind][CFL_PRED_V] == 0)
-    assert(signs[CFL_PRED_V] == CFL_SIGN_POS);
-
-  // Write a symbol representing a combination of alpha Cb and alpha Cr.
-  aom_write_symbol(w, ind, frame_ctx->cfl_alpha_cdf, CFL_ALPHABET_SIZE);
-
-  // Signs are only signaled for nonzero codes.
-  if (cfl_alpha_codes[ind][CFL_PRED_U] != 0)
-    aom_write_bit(w, signs[CFL_PRED_U]);
-  if (cfl_alpha_codes[ind][CFL_PRED_V] != 0)
-    aom_write_bit(w, signs[CFL_PRED_V]);
+static void write_cfl_alphas(FRAME_CONTEXT *const ec_ctx, int idx,
+                             int joint_sign, aom_writer *w) {
+  aom_write_symbol(w, joint_sign, ec_ctx->cfl_sign_cdf, CFL_JOINT_SIGNS);
+  // Magnitudes are only signaled for nonzero codes.
+  if (CFL_SIGN_U(joint_sign) != CFL_SIGN_ZERO) {
+    aom_cdf_prob *cdf_u = ec_ctx->cfl_alpha_cdf[CFL_CONTEXT_U(joint_sign)];
+    aom_write_symbol(w, CFL_IDX_U(idx), cdf_u, CFL_ALPHABET_SIZE);
+  }
+  if (CFL_SIGN_V(joint_sign) != CFL_SIGN_ZERO) {
+    aom_cdf_prob *cdf_v = ec_ctx->cfl_alpha_cdf[CFL_CONTEXT_V(joint_sign)];
+    aom_write_symbol(w, CFL_IDX_V(idx), cdf_v, CFL_ALPHABET_SIZE);
+  }
 }
 #endif