aomedia /
aom /
4f0b3ed8b8fa32a866c24e332406fd9187b23cf9 Retune the CLPF kernel
CLPF performance had degraded by about 0.5% over the past six months,
which isn't totally surprising since the codec is a moving target.
About half of that degradation comes from the improved 7 bit filter
coefficients. Therefore, CLPF needs to be retuned for the current
codec.
This patch makes two (normative) changes to the CLPF kernel:
* The clipping function was changed from clamp(x, -s, s) to
sign(x) * max(0, abs(x) - max(0, abs(x) - s +
(abs(x) >> (bitdepth - 3 - log2(s)))))
This adds a rampdown to 0 at -32 and 32 (for 8 bit, -128 & 128
for 10 bit, etc), so large differences are ignored.
* 8 taps instead of 6 taps:
1
4 3
13 31 -> 13 31
4 3
1
AWCY results: low delay high delay
PSNR: -0.40% -0.47%
PSNR HVS: 0.00% -0.11%
SSIM: -0.31% -0.39%
CIEDE 2000: -0.22% -0.31%
APSNR: -0.40% -0.48%
MS SSIM: 0.01% -0.12%
About 3/4 of the gains come from the new clipping function.
Change-Id: Idad9dc4004e71a9c7ec81ba62ebd12fb76fb044a
9 files changed
