shithub: libvpx

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ref: f1ce050f44c7f91ee941155c7e080e6640b12781
parent: 8099220e6c5e2cc8c857f85e1429d857c87a6f2a
author: paulwilkins <[email protected]>
date: Mon Dec 4 08:41:44 EST 2017

Bug fix for second reference stats.

Immediately following a key frame the trailing second reference
error in the first pass stats will be based on a reference frame from
the prior key frame group and will thus usually be much larger.

This fix eliminates that effect (which typically triggers a short arf
group immediately after a key frame). It also changes the accounting
for the first frame in each new arf group.

This change gives large gains on a couple of clips that contain mid
sequence key frames (e.g. 6% on 1080P tennis). Overall there was
a net gain in PSNR and PSNR-HVS ~(0.05- 0.4%) and mixed results for
SSIM (+/- 0.2%).

Change-Id: I8e00538ac2c0b5c2e7e637903cac329ce5c2a375

--- a/vp9/encoder/vp9_firstpass.c

+++ b/vp9/encoder/vp9_firstpass.c

@@ -2543,8 +2543,11 @@

       // Update the accumulator for second ref error difference.

       // This is intended to give an indication of how much the coded error is

       // increasing over time.

-      sr_accumulator += (next_frame.sr_coded_error - next_frame.coded_error);

-      sr_accumulator = VPXMAX(0.0, sr_accumulator);

+      if (i == 1) {

+        sr_accumulator += next_frame.coded_error;

+      } else {

+        sr_accumulator += (next_frame.sr_coded_error - next_frame.coded_error);

+      }

     }

     // Break out conditions.