MiniMax H3 profiling: VAE decode takes 43% of generation time (5.5 min per 15s clip on 4090)

Prestigious_Cat85 · reddit · 2026-08-20

After profiling 75 MiniMax H3 generations, a user identified VAE decoding as the main bottleneck. Generating a 15-second (362-frame) clip on an RTX 4090 takes about 5.5 minutes just for VAE decoding (0.85-1.0 s/frame), not sampling. Attempts like fp8mix VAE (3% gain), merging tasks (no amortization), and Sol-Attn (version conflict) were made. The user asks if a faster VAE exists, if CUDA 13/newer torch helps, and if tiling or temporal chunking can reduce decode time.

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