Introduce AC Bias

Description

Introduce AC Bias, an energy-preserving psycho-visual metric that helps increase subjective quality of video. This metric is based on the difference of the "energy" (SATD - SAD) of the source and reconstituted encoded blocks, similar to x264 and x265's implementation. Alternatively, a more lightweight rate adjustment mechanism based on total block "energy" (sum of transformed AC block coefficients) used by the Fast-PD0 and Fast-PD1 code paths is provided.

• Moderate values (1.0-1.5) help retain sharpness and acuity of textures and scenes with complex motion
• High values (4.0-6.0, together with disabling temporal filtering and CDEF) can dramatically improve film grain and noise retention

C, SSE2, AVX2 and NEON 4x4 and highbd 8x8 Hadamard functions were borrowed from libaom.

Issue

Part of the SVT-AV1-PSY mainlining effort (#2269)

Author(s)

@computerbuster @juliobbv

Performance impact

• quality
• memory
• speed
• 8 bit
• 10 bit
• N/A

Test set

• obj-1-fast can be found here
• other
• N/A

Merge method

• Allow the maintainer to squash and merge when PR is ready to create a 1-commit to the master branch. The maintainer will be able to fix typos / combine commit messages to create a more readable 1-commit message or use whatever is stated in the 'Description' section
• I will clean up my commits and the maintainer shall use 'rebase and merge' to the master branch