DMD needs an auxiliary network that tracks the generator's output distribution. APEX uses the generator itself. The original text condition generates, and the negated projected text (c_shift = -c) selects fake-velocity estimation with the same weights. The frozen teacher, Self-Replay Forcing and perceptual loss from S2-Avatar stay. The price is weaker motion.
š What changes
⢠One set of weights and, by default, shared AdamW states
⢠Inference uses only the generation path, then a one-step 2x Refiner
⢠The fake estimator is fitted to replay outputs; its clean-latent gap to the teacher gives a detached generator correction
š The numbers
⢠Vs DMD at matched settings: 102.7 to 98.2 GiB per GPU, 35.9 to 32.6 s per iteration
⢠Vs S2-Avatar, 70 paired 180 s cases at 3 NFE: instruction 22 wins, 47 ties, 1 loss; motion -8.6%
⢠Progressive VIF 3.856 vs 3.831, aesthetics 0.642 vs 0.633, pooled AVSync error 1.319 to 1.341 s
ā ļø Caveats
⢠One cost measurement with no variance reported; 70-case rounds with no significance tests
⢠Only 180 s avatar-style video at 1344x768, and the baseline is the authors' own recipe
Paper:
Few-Step Streaming Video Generation via Condition Shifting (2611.14033)
Would you accept a few percent in training savings and better prompt following in exchange for weaker motion?
š Read it elsewhere
⢠The deep dive on Medium: https://medium.com/p/fd4facc13c3f
⢠The long read on Substack: https://sajjadpakdamansavoji.substack.com/p/apex-drops-dmds-fake-score-network
⢠The thread on X: https://x.com/saavoji/status/2120949703953289381
⢠Every version on sajjadpsavoji.github.io: https://sajjadpsavoji.github.io/blog#apex-drops-dmds