When frame_overlap=0 and i2i_scene_cut=True, generates a new starting frame
for each continuation scene by denoising the previous scene's last frame with
the new scene prompt (i2i strength-controlled). The result is pinned as frame 0
of the next chunk (mask=0, i2v style), replacing soft continuation.
reference_frames output collects all generated anchor images as an IMAGE batch.
New inputs: i2i_scene_cut (BOOLEAN), i2i_strength (FLOAT 0.0–1.0).
New output: reference_frames (IMAGE, slot 2 — shifts status/scene_count/etc up by 1).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Remnants of the old append-guide-to-end approach (abandoned in e8c3b32).
The current prepend approach needs neither: the guide lands at temporal
position 0 naturally via the causal patchifier, no keyframe_idxs required.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Option 1 (samplers.py): Add optional clip input to FunPackLTXAVSceneChainSampler.
After each scene is sampled, decode its last frame and re-encode the next scene's
conditioning with that frame as vision context. This gives identical scene texts
different conditioning based on temporal position, so the model knows what state
it came from.
Option 2 (conditioning.py): When building scene conditionings, detect duplicate
scene texts and prepend "Returning to an earlier scene: " before encoding the
second+ occurrence. Stores original text in funpack_scene_text for logging and
the actual encode text in funpack_encode_text so the sampler uses the same prefix.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
When frame_overlap=0, use the last 4 frames of the previous scene as soft
continuation guides (mask=0.4) instead of a single fully-pinned frame (mask=0.0).
This lets the model use previous-scene context for identity continuity while
retaining freedom to change orientation from the text prompt. The frames land
at positions 1-4 after the i2v guide at position 0 (when carry_i2v_guides is
enabled). crop count is returned dynamically so the existing crop/blend logic
requires no changes.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Chain sampler accepts optional refinement_key_input (wire from the same
key as the V2 Refiner). On each run it calls update_refinement_sampler_context
to write carry_i2v_guides, frame_overlap, and scene count into the shared
state file. The V2 Refiner reads last_sampler_context from state when it
loads, making it available for the gen_context snapshot with no latent
manipulation and no extra Refiner inputs.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Chain sampler now embeds funpack_sampler_context into the output latent
(carry_i2v_guides, frame_overlap, transitions_enabled). V2 Refiner reads
these from its existing latent input — no new Refiner inputs needed.
Removed the three forceInput connectors added in the previous commit.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Add confirmed-bad-combo warnings to both parameter tooltips, the sampler
doc, and the changelog. Warn users not to combine frame_overlap=0 with
carry_i2v_guides=True in normal use.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
mask=0.5 caused the continuation frame to be partially denoised, distorting
it and triggering the same yellowing artifacts as the temporal position conflict.
mask=0.0 keeps the frame intact so the model uses it as a clean reference.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
When no overlap frames are pinned, the next scene has zero context from
the previous one. Prepend the last latent frame from the previous output
with mask=0.5 so the model can use it as a soft continuation reference
without hard-pinning it. The frame is cropped from the head after sampling
and never appears in the output. Works alongside carry_i2v_guides.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Appending the guide (even offset to chunk-end) caused the model to generate
content converging toward the reference at the end of each scene. Scene 3's
overlap started from that converged tail and compounded into a full visual reset.
Prepending the guide places it at temporal position 0 naturally (causal patchifier
assigns it [0,1]). Overlap frames follow at [1,9], [9,17]... — no temporal slot
conflict, no forward-pulling toward the reference. The guide acts as a clean
i2v anchor at the start. Crop now removes from the head after sampling.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Guide tokens were anchored at pixel position 0 (causal_fix default), which is the same
temporal slot occupied by the overlap frames at the start of continuation chunks. The model
saw two different frame contents claiming position 0 and produced color artifacts. Offset
the guide to chunk_end + 1 latent step so it acts as a forward style anchor instead.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Removed per-scene slicing (_decode_video/_decode_tensor) and the aggressive
del-before-decode GC block. Now: whole sampling loop runs to completion →
full latent decoded in one pass → transition pixel effects applied after.
LATENT output is unchanged. Per-scene decode was causing seam cross-contamination
anyway and contradicted the post-process-only contract for transitions.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Transition "bad" appearance: blend_half_pixels=64 caused 2+ seconds of
forced full-black at every seam — the flat zone existed to hide latent
blend artifacts, but the blend is a no-op (overlap frames are identical
on both sides, mask=0). Removed blend_half entirely. Transitions are now
a simple V-ramp: full effect at the seam center, linear ramp back to
normal over transition_duration//2 pixel frames on each side.
Memory leak: scene_cond (Python loop variable) stays alive after
del scene_conditionings — still holds the conditioning tuple whose
embedding tensor keeps LTXAVTEModel referenced during VAE decode.
Added scene_cond to the del statement.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
_append_i2v_guides only extends the VIDEO tensor by 'protected' frames.
The audio tensor is never touched, so sampled audio after sampling is
already the correct length. Cropping it proportionally removed audio
frames that were never added, making audio progressively shorter across
scenes and playing back faster.
Main's version (crop video only) was always correct.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
_match_audio_amplitude mutated the audio tensor of sampled before
_blend_latents, putting rescaled audio into the overlap zone that
becomes pinned context for the next scene. LTXAV generates video and
audio jointly — artificially rescaled audio context degrades video
generation quality, causing progressive burnout across scenes.
Also removed dead code: _has_i2v_reference_latent (defined, never
called), _build_bridge_chunk_UNUSED, and want_latent (unused after
transition-path cleanup). Sampling loop now matches main exactly
except for boundary_entries metadata tracking (read-only).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
_crop_video_tail was only cropping the video tensor, leaving audio at its
full (guide-appended) length. _blend_latents then computed audio overlap
from the wrong video/audio ratio — too many audio frames removed per seam —
so audio drifted progressively shorter than video and played back faster
with each additional scene.
Fix: crop all non-video tensors (audio) proportionally using _derived_overlap,
the same ratio logic used everywhere else in the blend path.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
The NestedTensor fix was based on a wrong assumption — workflow separates
video and audio latents before decoding each independently. Reverted.
Actual cause of gradual burnout: decoding the full concatenated multi-scene
latent in one VAE pass lets temporal attention spread seam artifacts forward
across scenes. Each additional scene adds another seam, compounding the damage.
Fix: decode each scene's latent slice independently using the known boundary
positions from boundary_entries, then concatenate pixel frames. Transitions
are applied on the concatenated pixels as before. The VAE never sees across
a scene boundary.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
_decode_video was extracting only the video tensor before calling vae.decode(),
stripping the audio component. LTXAV's video decoder uses audio as temporal
conditioning — without it, decode quality degrades progressively across scenes
(causal: later frames suffer most) and audio timing drifts.
Standard ComfyUI decode passes output["samples"] directly (full NestedTensor).
Match that behavior. Tiled path still extracts video tensor since decode_tiled
likely doesn't support NestedTensor, falling back to full decode on failure.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Was added to hide yellow seam artifacts, but those are gone now that
transitions run as pure post-process on a full-video decode. Blur
effect is blur only, no fade to black.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Transitions apply in pixel space after all sampling is complete.
LATENT output is always the raw generated latent, untouched.
IMAGE output decodes the finished latent and applies pixel effects directly.
No re-encode path exists — removed _apply_transitions_latent entirely.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
blur_out_in blurred center frames but never dimmed them — the yellow decode
artifact at the seam was fully visible through the blur. Added the same
brightness ramp as fade_to_black so center dims to 0; blur and fade now
happen together so the seam is both blurry and invisible.
_apply_transitions_latent was decoding individual windows around each
boundary and re-encoding them back into the latent. Window edges lack full
temporal context, so the VAE encoder introduced color artifacts. Replaced
with full-video decode → pixel transition (same as the IMAGE path) →
full-video re-encode, giving the VAE correct context everywhere.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Transition center was placed at cumulative_latent_frames - overlap//2,
inside scene 1's territory. Since overlap frames are pinned (mask=0)
the latent blend is a no-op, so the actual content seam is at
cumulative_latent_frames exactly. Centering there puts the seam at
peak black, hiding any decode artifacts and giving a clean post-processed
fade-to-black feel on each side.
Maps stacking: _capture_finalizer merged new captures with the existing
temp file, including leftovers from previous ComfyUI runs. Each "loved it"
cycle blessed maps that had been tainted by the previous round's injection,
compounding color bias indefinitely. Clear the temp file at build_enhancements
start so each generation captures clean.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
del model/positive/negative was not enough — the loop leaves
scene_conditionings (slice of positive), scene_positive, scene_negative,
chunk, and sampled alive after the loop. All hold conditioning tuples
whose embedding tensors keep the text encoder referenced. Delete all of
them before VAE decode so ComfyUI can unload the TE immediately.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Revert anchor source back to blended cumulative output — prev_sampled
gave scene N+2 a tail dominated by scene N-1 pinned frames, weakening
the scene-N representation and making the i2v guide's reference pull
visually dominant (apparent reset to reference image). Blended anchor
frames are already hidden by the coverage fix so no yellow leaks.
Fix blur edge distortion: avg_pool2d with zero-padding darkened image
edges at high sigma. Now pre-pad with reflect mode and pool with
padding=0, eliminating the dark halo at frame boundaries.
Fix effect curve shape: previous linear V-fade left blended-latent
content visible at ~89% brightness at the blend zone edges, giving a
"generated transition frames" look. New shape holds brightness=0 /
sigma=max flat across the entire blend zone, then ramps back to full
over transition_duration//2 extra frames into clean scene content.
The blend zone is now fully hidden regardless of transition_duration.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
_build_continuation_chunk was reading from the blended cumulative
output whose tail (for 3+ scenes) contains interpolated latent frames
from earlier overlap zones. These decode with color artifacts and were
polluting the anchor context for later scenes.
Store prev_sampled per iteration and use it as the anchor source.
The blended output is still used for the final assembled video and
for cumulative_latent_frames accounting; only the anchor source
changes. Transitions remain purely post-process.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
- transition_duration=0 now fully skips boundary recording and all
effect application (previously min was 2 and effects always ran)
- Pixel path: half now covers the full blend zone (blend_half_pixels =
video_overlap//2 * time_scale) plus transition_duration//2 extra
frames, so blended latent artifacts are no longer visible outside
the fade region
- Latent path: half_lat now covers blend_half_latent + extra_lat so
the re-encode window includes the full overlap zone; half_pix uses
the full decoded window so the VAE round-trip frames are all faded
- blend_half_latent/blend_half_pixels stored per boundary entry so
each boundary uses the correct overlap geometry
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Delete model/positive/negative references before calling vae.decode() so
ComfyUI's model manager can unload the diffusion model and text encoder
cleanly. Previously they stayed live as function parameters, causing the
circular-reference warning.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
- Detect which outputs are connected via the ComfyUI prompt graph
- IMAGE connected: full decode → pixel transitions → IMAGE (no re-encode)
- LATENT only: window decode → effect → re-encode → splice (original approach)
- Both: pixel path for IMAGE; LATENT is the raw combined output unchanged
- Add decode_tile_size optional input for OOM control
- Split logic into _apply_effect_on_pixels / _apply_transitions_pixel /
_apply_transitions_latent / _decode_video for clarity
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Custom transition triggers in Studio can now have a visual_effect assigned
(fade_to_black, crossfade, blur_out_in). When triggered during scene splitting,
the effect fires at that scene boundary: the sampler decodes the latent window
around the boundary, applies the pixel-space effect, and re-encodes in-place.
No new nodes needed — VAE is already connected to the scene chain sampler.
New transition_duration input controls how many pixel frames are affected.
New scene_boundaries output provides the boundary list for debugging.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Attempted both approaches:
1. Bridge to reference image - visible reset, character snaps back to reference
2. Two-pass: generate scenes independently, bridge between actual scene frames -
still resets to reference because each independently generated scene
starts from the i2v reference frame (it IS the first frame)
Root cause: LTX-2's first-last-frame conditioning anchors outputs to the
pinned frames too strongly. When the "last frame" target is the reference
image (as the start of any scene), the bridge always transitions TO that
reference, producing the exact reset effect we were trying to avoid.
Would require scenes generated without any reference anchor for the
bridge target to be a natural scene composition - which breaks character
consistency. No clean solution without IP-Adapter or equivalent.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Previous implementation bridged scene N → reference image, which caused
a visible "reset to reference" rather than a smooth transition.
Correct approach (matches LTX Desktop Bridge Shots):
1. Generate ALL scenes independently from latent_template
2. For each consecutive pair, generate a bridge:
- First frame = last frame of scene N
- Last frame = first frame of scene N+1
- Middle = denoised by the model
3. Assemble: scene1 + bridge + scene2 + bridge + scene3 + ...
The model now transitions between where scene N actually ended and where
scene N+1 actually begins, not to a static reference reset.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
New boolean input: bridge_shots (default False). When enabled, generates
a short transition clip between scenes by pinning both ends:
- First frame = last frame of the previous scene (where we came from)
- Last frame = first protected frame of the i2v latent (reference image)
- Middle = denoised by the model with the scene's conditioning
Duration: 30 video frames (~1 second at 30fps). Only fires when an i2v
reference is detected in the latent template (noise_mask present with
first frame mask < 0.95). Falls back to standard overlap if no i2v
reference is connected.
Status line reports bridge count. Scene report lists bridge seeds.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Audio continuation chunks mix real latents (overlap context from prev
scene, low std) with template noise (new frames, std ~1). The model
denoises new frames anchored by the low-amplitude context, producing
quieter audio in every scene after the first.
After sampling each continuation scene, measure the RMS of the overlap
audio frames (known good amplitude from previous scene) and the RMS of
the newly generated frames. If the discrepancy is >10%, rescale the new
frames to match the overlap RMS before blending.
Scene 1 is unaffected (no overlap, no adjustment). Video latents are
never touched.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
New sampler targeting LTX2.3 distilled LoRA and similar 4-8 step
flow-matching distilled video models. Three improvements over plain Euler:
Adams-Bashforth 2-step multistep (order=2, default):
Extrapolates the denoised direction from two consecutive steps using
variable-step-size AB2 coefficients: (1 + r/2) * d_curr - (r/2) * d_prev
where r = h_current / h_previous. Gives second-order accuracy across the
large sigma jumps typical of distilled schedules at zero extra model-call cost.
Heun predictor-corrector on final steps (final_correction_steps=1, default):
Replaces the last N steps with a Heun pass: Euler predictor to sigma_next,
second model call at sigma_next for the corrector direction, averaged update.
Costs one extra model call per corrected step and significantly improves
sharpness and detail in the steps that define the final output.
Multistep history is invalidated after each Heun step.
Optional s_noise (default 0.0 = deterministic):
Small ancestral-style noise injection (scaled by sigma_up) for diversity.
Distilled models are trained as pure ODE; any non-zero value is an
intentional deviation. Keep below 0.15 if used at all.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Order-2 ancestral denoised extrapolation (automatic, zero extra cost):
The early Euler-A phase now reuses the previous step's denoised output
to extrapolate a better score direction estimate before each ancestral
step, equivalent to DPM-Solver++ 2M applied to the stochastic phase.
The state is reset after any motion pulse since a pulse modifies x and
invalidates the previous estimate.
Progressive correction_blend in quality phase (automatic, speeds up):
The first half of quality-phase steps now use correction_blend=0
(single-eval Euler ODE); the second half use the configured blend
(full 2S correction). _hybrid_ode_step already returns early at blend=0
with no second model call. For a 30-step run with 35% quality phase this
saves roughly 4-5 model calls (~12% faster) while keeping the expensive
2S correction where sigma is lowest and it has the most impact.
Adaptive eta decay (new eta_final parameter, default 1.0):
When eta_final is set below eta, ancestral noise strength decays linearly
toward eta_final as sigma approaches the quality boundary, based on
sigma proximity (quality_sigma_start / sigma). This reduces stochastic
variation right before the deterministic quality phase, giving a cleaner
hand-off. Default 1.0 preserves existing behaviour.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
