tree a16b120dc068b75e3b3b2d2171bd599f0566af19
parent bdfec11ae674d6319e947dea90709bf9985893f8
author Hui Su <huisu@google.com> 1563314405 -0700
committer Hui Su <huisu@google.com> 1563389127 +0000

Adjust RD mult for keyframe in Q mode

Use slightly lower RD multiplier for keyframe when the qindex is between
64 and 192 in fixed-q mode. The formula is experimentally selected.

It improves encoding quality metrics slightly.

Speed 1, PSNR
NO. frames	lowres	midres	ugc360
      50	-0.03%	-0.09%	0%
     100	0.00%	-0.07%	-0.04%
     150	-0.03%	-0.09%	-0.03%

Speed 1, SSIM
NO. frames	lowres	midres	ugc360
      50	-0.23%	-0.28%	-0.09%
     100	-0.10%	-0.20%	-0.14%
     150	-0.15%	-0.15%	-0.02%

Speed 2, PSNR
NO. frames	lowres	midres	ugc360
      50	-0.02%	-0.06%	-0.07%
     100	-0.01%	-0.05%	-0.05%
     150	-0.02%	-0.09%	-0.03%

Speed 2, SSIM
NO. frames	lowres	midres	ugc360
      50	-0.31%	-0.24%	-0.12%
     100	-0.14%	-0.23%	-0.17%
     150	-0.15%	-0.23%	-0.13%

Change-Id: I06031a2eea6ce6154835dcc5170e63f0afcf3e2e