Add reduced-overhead entropy coder

Multimedia / Daala - Timothy B. Terriberry [xiph.org] - 11 August 2015 15:43 UTC

This adds an alternative to partition function for mapping values from frequency counts to the coder's current range. The new function is about 3x as complex as the old one, but is a better approximation of the ideal function, while still having an order of magnitude less complexity than a division. The inverse mapping does require division by the constant three, but this can be turned into multiplication (or avoided entirely).

Metrics on ntt-short-1: RATE (%) DSNR (dB) PSNR -0.33121 0.01085 PSNRHVS -0.37603 0.01932 SSIM -0.26811 0.00666 FASTSSIM -0.30768 0.00893

47a4f65 Add reduced-overhead entropy coder.
src/entcode.h | 62 +++++++++++++++++++++++++++++++++++
src/entdec.c | 101 ++++++++++++++++++++++++++++++++++++++++++++++++++++-----
src/entenc.c | 38 ++++++++++++++++++++++
3 files changed, 193 insertions(+), 8 deletions(-)

Upstream: git.xiph.org

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