tree dc7c6c6521ca25c6fcea8095e3dfd8aa7eda80a6
parent d6a3d66f43104400dac078a2ab99526d806773af
author bohanli <bohanli@google.com> 1581623588 -0800
committer Bohan Li <bohanli@google.com> 1581799760 +0000

Add adaptive shrinking of gf group length.

Generally we want to place the altref on somewhere with lower
error/motion, so it could help more frames. This patch determines
the high/low errors regions from first pass stats, and uses it to
determine whether we want to shrink the gf group. Around 0.5% gain
on average PSNR and 0.4% gain on overall PSNR are observed on
speed4 test:

	avgPSNR	  overallPSNR 	 ssim		VMAF
lowres	-0.466	  -0.410	 -0.441		-0.487
midres	-0.335	  -0.325	 -0.347		-0.341
ugc360p	-0.746	  -0.551	 -0.455		-0.596

Speed1 test results are similar with a smaller gain:
       (on ugc360p there is one sequence with bad performance
        that was not present on speed4, may be related to
        parameter tuning on speed4.)
	avgPSNR	  overallPSNR 	 ssim		VMAF
lowres	-0.322	  -0.264	 -0.262	        -0.270
midres	-0.330	  -0.341	 -0.332	        -0.350
ugc360p	-0.433	  -0.116	 -0.124	        -0.188

STATS_CHANGED

Change-Id: I89cdeba5483bd75b20ad090675fea1a715a07a0d