Blur detection — head-to-head comparison

Same 5000 crops scored by two complementary methods:

• Cepstrum — numpy/scipy FFT analysis. Detects directional smear (motion blur, camera shake). ~3 ms/img.
• MUSIQ — Google's deep no-reference IQA (via pyiqa, KonIQ-trained). Captures general quality including blur, compression, low texture. ~350 ms/img.

Rank correlations (higher=stronger agreement on "this is bad"):

cepstrum  vs  MUSIQ        : +0.078
cepstrum  vs  q_lap_var    : +0.084
MUSIQ     vs  q_lap_var    : +0.425