The opening frame came out noisy because the cut was made in latent space. The
LTX video VAE is causal: latent frame 0 is the temporal origin and decodes to a
single pixel frame, while every later latent frame was generated as a
CONTINUATION of the frames before it. Slicing the front off the latent promoted
a continuation frame to position 0, and the decoder then applied the
temporal-origin handling that frame was never generated for. H3 already cut
decoded images for unrelated reasons and so never had the bug; LTX now does the
same thing.
The count was wrong too, quietly. A latent cut could only remove whole latent
frames, and the promoted frame changed from covering 1 pixel to covering
`scale`, so dropping k latent frames shortened the clip by k*scale rather than
the (k-1)*scale+1 it actually spanned. The value was also rounded up to a whole
latent frame on the way in. It is now exact: N means N, matching H3.
Each eligible scene records a (start, count) pixel span instead of cutting; the
spans are removed after decode, later ones first so earlier removals cannot
shift their indices. Mid-chain hard-cut scenes keep working — the span is
computed from the scene's position in the chain, which is exact because anchor
scenes append with zero blend overlap. The latent's audio stream loses the same
stretches of TIME, mapped by proportion on its own axis, or sound would run
ahead of picture with no error. The latent's VIDEO stream is deliberately left
whole (cutting it is the bug), so video comes from the IMAGES output — which the
Editor already wires. A run with IMAGES unconnected now skips with a reason
instead of silently doing nothing.
_cut_opening_latent is removed rather than left dead, since its docstring
documented the broken approach as correct.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
