tree 38ac1bffe0509785bf1d03bafb0584b8d3b0be5d
parent 530b304f03c6987cf1d098f3853e4224b31a08c7
author Zoe Liu <zoeliu@google.com> 1502835330 -0700
committer Zoe Liu <zoeliu@google.com> 1503315019 +0000

Tune the decision on the GF group interval

The change is purely an encoder-side tuning, which constrains a GF
group interval to be either 8, or 12, or a number larger than 12
(maximum of 16). The change is under ext_refs.

This work has been part of the summer internship effort by chendixi@.

Further, this CL removes the experiment of flex_refs and merges it
into ext_refs, as flex_refs has been completely focused on the encoder
side optimization for ext_refs.

On Google test sets, above (stillness + interval enforcement) achieve
a coding gain in BDRate as follows, compared against the AV1 baseline
with all tools enabled by default (excluding ext-tx, global-motion,
and convolve-round for speed concern):

lowres: avg_psnr -0.193%; ovr_psnr -0.370%; ssim -0.332%
midres: avg_psnr -0.556%; ovr_psnr -0.680%; ssim -0.798%

Change-Id: Ia992d8ef0d82cc0ef2caba5eec9b26f0358e6bde