commit fcf5fa2723524fe2beabd2b0ac1d4409a2284405
author Zoe Liu <zoeliu@google.com> Mon Jun 26 16:00:38 2017 -0700
committer Zoe Liu <zoeliu@google.com> Wed Jul 12 00:20:35 2017 +0000
tree 7afe2e2695de320f7b6046b55676ba4f097753b3
parent 9c52192b10b054559edb6e34af9a946e2868f2d7

Further work on ext-comp-refs for ref frame coding

(1) Work with var-refs to remove redundant bits in ref frame
    coding;
(2) Add a new uni-directional compound reference pair:
    (LAST_FRAME, LAST3_FRAME);
(3) Redesign the contexts for encoding uni-directional reference frame
    pairs;
(4) Use aom_entropy_optimizer to collect stats for all the default
    probability setups related to the coding of reference frames.

Compared against the baseline (default enabled tools excluding ext-tx
and global-motion for encoder speed concern) with one-sided-compound,
the coding gain of ext-comp-refs + var-refs - one-sided-compound is:

lowres: avg_psnr -0.385%; ovr_psnr -0.378% ssim -0.344%
midres: avg_psnr -0.466%; ovr_psnr -0.447% ssim -0.513%

AWCY - High Latency:
   PSNR | PSNR Cb | PSNR Cr | PSNR HVS |    SSIM | MS SSIM | CIEDE 2000
-0.2758 | -0.1526 | -0.0965 |  -0.2581 | -0.2492 | -0.2534 |    -0.2118

AWCY - Low Latency:
   PSNR | PSNR Cb | PSNR Cr | PSNR HVS |    SSIM | MS SSIM | CIEDE 2000
-1.0467 | -1.4500 | -0.9732 |  -0.9928 | -1.0407 | -1.0180 |    -1.0049

Compared against the baseline (default enabled tools excluding ext-tx
and global-motion for encoder speed concern) without
one-sided-compound, the coding gain of
ext-comp-refs + var-refs - one-sided-compound is:

lowres: avg_psnr -0.875%; ovr_psnr -0.877% ssim -0.895%
midres: avg_psnr -0.824%; ovr_psnr -0.802% ssim -0.843%

Change-Id: I8de774c9a74c20632ea93ccb0c17779fa94431cb

av1/common/blockd.h

diff --git a/av1/common/blockd.h b/av1/common/blockd.h
index 6bf892a..bfdf48b 100644
--- a/av1/common/blockd.h
+++ b/av1/common/blockd.h
@@ -518,6 +518,7 @@
 static INLINE MV_REFERENCE_FRAME comp_ref0(int ref_idx) {
   static const MV_REFERENCE_FRAME lut[] = {
     LAST_FRAME,    // LAST_LAST2_FRAMES,
+    LAST_FRAME,    // LAST_LAST3_FRAMES,
     LAST_FRAME,    // LAST_GOLDEN_FRAMES,
     BWDREF_FRAME,  // BWDREF_ALTREF_FRAMES,
   };
@@ -528,6 +529,7 @@
 static INLINE MV_REFERENCE_FRAME comp_ref1(int ref_idx) {
   static const MV_REFERENCE_FRAME lut[] = {
     LAST2_FRAME,   // LAST_LAST2_FRAMES,
+    LAST3_FRAME,   // LAST_LAST3_FRAMES,
     GOLDEN_FRAME,  // LAST_GOLDEN_FRAMES,
     ALTREF_FRAME,  // BWDREF_ALTREF_FRAMES,
   };
@@ -621,8 +623,6 @@
   YV12_BUFFER_CONFIG *buf;
   struct scale_factors sf;
 #if CONFIG_VAR_REFS
-  // TODO(zoeliu): To evaluate whether "is_valid" is needed or the use of it can
-  // be simply replaced by checking the "idx".
   int is_valid;
 #endif  // CONFIG_VAR_REFS
 } RefBuffer;