Overview: Quality metrics

Video quality metrics compare pictures through numerical models that measure particular kinds of difference.

A quality score is the output of a defined comparison, not a direct measurement of every viewer's preference. PSNR, SSIM and VMAF examine different relationships between a reference and a processed picture. Their pages explain what a score represents so the metric can be used alongside visible evidence.

• VMAF
  VMAF predicts perceived video quality by comparing a decoded test video with a reference under a selected model and viewing context.

• PSNR
  PSNR expresses decoded sample error relative to a declared peak value using a logarithmic decibel scale.

• SSIM
  SSIM compares local luminance, contrast, and structure between decoded pictures and a reference.