olivv-cs-ComfyUI-FunPack/docs/FunPackLTXAVSceneChainSampler.md

FunPack LTXAV Scene Chain Sampler

FunPack LTXAV Scene Chain Sampler samples multi-entry scene conditioning as one smooth continuation run.

Use it with FunPack Studio or FunPack Video Refiner V2 when split_by_transitions is enabled. The refiner returns one positive conditioning entry per detected scene, and this sampler uses each entry for one sequential chunk.

You can also use it without Studio. Encode each scene separately, then combine those conditioning outputs with ComfyUI's ConditioningCombine. The sampler treats each conditioning entry in the combined list as one scene.

Important: this sampler is resource heavy. Long chains can produce very large final latents. You may run out of memory during VAE Decode even if every sampling chunk completed successfully.

Inputs

• model: LTXV or LTXAV model.
• vae: VAE with the LTX time scale metadata.
• positive: Scene conditioning list. One entry becomes one generated scene.
• negative: Negative conditioning shared by every scene.
• sampler: ComfyUI sampler object, for example from Studio's sampler output.
• sigmas: Sigma schedule for each chunk.
• seed: Base seed. Scene N uses seed + N unless scene seed metadata is present.
• latent_template: One scene-sized latent template. Plain video and nested AV latents are supported.
• num_frames_per_scene: Pixel frame count represented by latent_template.
• frame_overlap: Pixel frames to preserve and blend between scene chunks. Set to 0 to disable overlap entirely. Warning: combining frame_overlap=0 with carry_i2v_guides=True is confirmed to produce bad results — use only for testing.
• cfg: Internal CFG value.
• max_scenes: Maximum scene entries to consume. Default is 8, but it can be raised for longer chains.
• use_same_seed: When off, each scene uses funpack_scene_seed metadata from Studio/Refiner split mode, falling back to seed + scene_index. When on, every scene uses the first provided scene seed or the base seed.
• carry_i2v_guides: Experimental. Appends protected frames from latent_template's noise_mask as hidden LTX guide tokens in each continuation chunk. Default is off. Warning: using this with frame_overlap=0 is confirmed to produce bad results — enable only for testing.
• clip (optional): Connect the same CLIP as your Studio node. When provided, the sampler re-encodes each scene's conditioning after the previous scene finishes sampling, using the decoded last frame as visual context via Gemma3 vision. This gives identical scene texts genuinely different conditioning and lets the model reason about what state it came from when entering each new scene. Only active when the CLIP has vision capability (Gemma3-12B checkpoint with SigLIP weights). Safe to leave disconnected — behaviour is unchanged without it.

Behavior

The first scene samples from a fresh copy of latent_template.

Each following scene copies the previous output tail into the start of the next chunk, masks that overlap so it is preserved during denoising, samples the new frames with that scene's conditioning, then blends the overlap in latent space.

When Studio or Refiner V2 split mode provides scene seed metadata, the sampler reports and uses those exact seeds. This lets successful seed memory replay a known-good scene seed set while keeping the public Studio seed output as a single integer.

When carry_i2v_guides is enabled, protected source frames from the incoming latent_template are appended as guide tokens with keyframe_idxs and guide_attention_entries, then cropped away after sampling. This follows the same broad idea as LTX guide/IC-LoRA conditioning: the reference is extra context, not a visible frame inserted into the generated timeline. Keep it off unless you are testing that behavior deliberately. Combining carry_i2v_guides=True with frame_overlap=0 is confirmed to produce bad results and is not recommended for normal use.

For nested LTXAV latents, video and audio tensors are continued together. Audio overlap is derived from the audio/video latent length ratio.

Notes

Multi-entry conditioning from split_by_transitions is meant for this sampler. Connecting it to a normal sampler can mix scene conditionings together instead of routing one scene per chunk.

For manual workflows, use ConditioningCombine, not ConditioningConcat, when you want multiple scenes. ConditioningCombine preserves separate conditioning entries. ConditioningConcat merges token tensors into a single conditioning entry, so the sampler correctly sees it as one scene because no scene boundary remains.

Scene order is first in, first out. Written labels like scene ten, scene -999999, or scene minus infinity are treated as transition text only. They do not assign scene numbers.

For character consistency, keep the character or subject description before the first transition. Refiner V2 and Studio prepend that prefix to every detected scene conditioning.

VAE Decode memory use grows with the final stitched latent length. If decode fails with OOM, reduce max_scenes, lower num_frames_per_scene, decode shorter chains, or use a lower-memory decode path if your workflow provides one.