From: Ronald S. Bultje <rbultje@google.com>
Date: Sat, 12 May 2012 00:48:20 +0000 (-0700)
Subject: Don't use compound prediction for golden frames based on alt-ref frames.
X-Git-Tag: v1.3.0~1217^2~379^2~40^2
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=959b296a40a8b2111cff474e039034fc41f17aa9;p=libvpx

Don't use compound prediction for golden frames based on alt-ref frames.

These frames can force reference frame (arf), mode (zeromv) and skip,
which means that if we use compound prediction (i.e. arf+last), we
might use a blend of a perfect (arf) and an imperfect (last) predictor,
leading to semi-garbage display and thus a huge drop in SSIM/PSNR (up
to 10dB for some frames I analyzed).

Gives a +0.2% gain on YT.

Change-Id: If1f2b7899ad165684af3808fd379295e82558cbb
---

diff --git a/vp8/encoder/encodeframe.c b/vp8/encoder/encodeframe.c
index a044f8cb9..ec3e1602c 100644
--- a/vp8/encoder/encodeframe.c
+++ b/vp8/encoder/encodeframe.c
@@ -1288,11 +1288,13 @@ void vp8_encode_frame(VP8_COMP *cpi)
         else
             frame_type = 2;
 
-        if (cpi->rd_prediction_type_threshes[frame_type][1] >
-                cpi->rd_prediction_type_threshes[frame_type][0] &&
-            cpi->rd_prediction_type_threshes[frame_type][1] >
-                cpi->rd_prediction_type_threshes[frame_type][2] &&
-            check_dual_ref_flags(cpi))
+        if (frame_type == 3)
+            pred_type = SINGLE_PREDICTION_ONLY;
+        else if (cpi->rd_prediction_type_threshes[frame_type][1] >
+                    cpi->rd_prediction_type_threshes[frame_type][0] &&
+                 cpi->rd_prediction_type_threshes[frame_type][1] >
+                    cpi->rd_prediction_type_threshes[frame_type][2] &&
+                 check_dual_ref_flags(cpi))
             pred_type = COMP_PREDICTION_ONLY;
         else if (cpi->rd_prediction_type_threshes[frame_type][0] >
                     cpi->rd_prediction_type_threshes[frame_type][1] &&