3 ms·

Sounds more like trellis quantization in near-lossless H.264, explicitly trading coding cost of details against psychovisual impact of said details.

• astrange 5y ago
  That's psy-rd (in x264 terms). Trellis quantization is just a more optimal way to divide numbers - think of it like rounding to nearest instead of down. "optimal" means "optimal rate-distortion tradeoff" and "distortion" means whatever you want it to, but usually it's difference between original and compressed pixels (absolute error/SAD/PSNR). That can look blurry, because given all alternatives with the same SAD, blurry ones compress more. So psy-rd changes the definition of distortion to add a "has similar amount of noise" factor. That's very far from human optimal (if anything it's SSIM optimal) but it's free detail. Uses the same quantization to get there, though.