From 8915eb8e9ae69b7ccd7a8b8666ad78667574d766 Mon Sep 17 00:00:00 2001
From: Jingning Han <jingning@google.com>
Date: Wed, 27 Jul 2016 09:12:53 -0700
Subject: [PATCH] Separate frame context index for different frame types

This commit makes the encoder to use different frame context index
for different frame types. In the baseline setting, it sets the
frame context index of the overlay frame to be different from other
regular inter frames. In the ext-refs setting, it further allows
the backward reference frame to use a different index.

It improves the compression performance for both settings.

Baseline
lowres  0.12%

ext-refs
lowres  0.50%
midres  0.56%

Change-Id: I7c63ddec9fc296c56a86353cf2c661a740b97a97
---
 vp10/common/onyxc_int.h |  5 +++++
 vp10/encoder/encoder.c  | 13 ++++++++++++-
 vp10/encoder/encoder.h  | 15 +++++++++++++++
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/vp10/common/onyxc_int.h b/vp10/common/onyxc_int.h
index 37f7631c7..1225540f4 100644
--- a/vp10/common/onyxc_int.h
+++ b/vp10/common/onyxc_int.h
@@ -47,7 +47,12 @@ extern "C" {
 // normal reference pool.
 #define FRAME_BUFFERS (REF_FRAMES + 7)
 
+#if CONFIG_EXT_REFS
+#define FRAME_CONTEXTS_LOG2 3
+#else
 #define FRAME_CONTEXTS_LOG2 2
+#endif
+
 #define FRAME_CONTEXTS (1 << FRAME_CONTEXTS_LOG2)
 
 #define NUM_PING_PONG_BUFFERS 2
diff --git a/vp10/encoder/encoder.c b/vp10/encoder/encoder.c
index 0620b885c..76ddea2de 100644
--- a/vp10/encoder/encoder.c
+++ b/vp10/encoder/encoder.c
@@ -285,7 +285,18 @@ static void setup_frame(VP10_COMP *cpi) {
   if (frame_is_intra_only(cm) || cm->error_resilient_mode) {
     vp10_setup_past_independence(cm);
   } else {
-    cm->frame_context_idx = cpi->refresh_alt_ref_frame;
+    if (cpi->refresh_alt_ref_frame)
+      cm->frame_context_idx = ARF_FRAME;
+    else if (cpi->rc.is_src_frame_alt_ref)
+      cm->frame_context_idx = OVERLAY_FRAME;
+    else if (cpi->refresh_golden_frame)
+      cm->frame_context_idx = GLD_FRAME;
+#if CONFIG_EXT_REFS
+    else if (cpi->refresh_bwd_ref_frame)
+      cm->frame_context_idx = BRF_FRAME;
+#endif
+    else
+      cm->frame_context_idx = REGULAR_FRAME;
   }
 
   if (cm->frame_type == KEY_FRAME) {
diff --git a/vp10/encoder/encoder.h b/vp10/encoder/encoder.h
index 63a1669f8..e1a155e76 100644
--- a/vp10/encoder/encoder.h
+++ b/vp10/encoder/encoder.h
@@ -75,6 +75,21 @@ typedef struct {
   FRAME_CONTEXT fc;
 } CODING_CONTEXT;
 
+typedef enum {
+  // regular inter frame
+  REGULAR_FRAME = 0,
+  // alternate reference frame
+  ARF_FRAME = 1,
+  // overlay frame
+  OVERLAY_FRAME = 2,
+  // golden frame
+  GLD_FRAME = 3,
+#if CONFIG_EXT_REFS
+  // backward reference frame
+  BRF_FRAME = 4,
+#endif
+} FRAME_CONTEXT_INDEX;
+
 typedef enum {
   // encode_breakout is disabled.
   ENCODE_BREAKOUT_DISABLED = 0,