Root cause of white noise: backpropagating through vae.decode produces
unstable gradients — the VAE decoder was designed for inference only.
Fix: encode reference clips to VAE latent space once (no grad), compute
mean + Gram matrix statistics there, and compute style loss directly on
net_generator.unnormalize(x) — a single differentiable linear operation.
The gradient path is now: loss → x (unnormalized) → ODE → x0, with no
decoder in the backward pass.
Also adds VAE encoder availability check (fails cleanly if encoder was
deleted to save VRAM).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
EthanfelandClaude Sonnet 4.6
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