A dependency-light Python script that computes SSIM between two image or frame files from first principles. It prints the three comparison terms (luminance, contrast, structure) on whole-image statistics, then the proper windowed Mean SSIM using an 11x11 Gaussian window (sigma 1.5) per the 2004 paper — reporting both the mean and the worst window the mean hides. Includes the equivalent FFmpeg ssim/libvmaf commands and the ssim_db formula in comments, and notes why FFmpeg's 8x8 stride-4 result di
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The handbook · 7 volumes
Fora Soft Video Engineering Handbook
This Python script computes SSIM from first principles and reports the worst window that the mean hides, with matching FFmpeg commands. Our seven-volume handbook covers where that score fits: Volume 1 on quality metrics such as PSNR, SSIM and VMAF and how encoders are tuned against them, Volume 3 on QoE in delivery, and Volume 6 on AI-based quality models. Written by Nikolay Sapunov, CEO at Fora Soft.
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