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>
Engine settings were unreadable: every experimental knob carried a paragraph
about cost figures, sampler caveats and failure modes, so nobody read any of
it. The hint is now ONE sentence saying what the setting does, and the
paragraph moves behind a collapsed "Details" link — still the only place some
of those numbers exist, just not in the way of the checkbox.
cut_opening_frames also learns MiniMax H3. It could never engage there: H3's
anchor is a keyframe condition row rather than a pinned latent prefix, so the
t2v guard read every H3 scene as anchorless, and its video latent sits on a
5k+2 grid an arbitrary cut cannot land on. On H3 the frames now come off the
head of the DECODED batch instead — exact to the frame — with the latent's
audio stream cropped by the same proportion of time, because audio decodes
from this node's LATENT output and would otherwise start N frames early. The
latent keeps its full video stream (off-grid the moment it is cut) and the
scene report says so.
Fixes a latent bug on the way: extra streams were cropped on dim 2 with the
video stream's frame count. On H3 dim 2 is the stereo channel and time is
last, so that would have cropped the audio to mono and left its duration
untouched.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The two-pass shift regrew the frames it dropped, and the invented ending
consistently came out with worse or missing movement — not worth paying
steps for. What is left is the part that works: generate the scene exactly
as normal, anchor pinned at full strength the whole way, then cut the
opening off the finished clip. Nothing is regrown, so the scene comes out
that much shorter and the audio is cropped to match.
Six knobs collapse into one INT, cut_opening_frames (0 = off), in the
Editor under Chain Sampler ▸ Timing & Seed rather than Experimental.
Gone with the shift: the mid-schedule split, the rewind re-noise
(_renoise_to_sigma), the tail refill modes, the fresh-audio reset, and the
schedule_context/continue_from_state plumbing that existed only so a split
scene would not re-time the sampler inside each half.
second_pass is untouched — it never used any of that machinery.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
