LTX-2 / LTX-2.3

LTX-2 is Lightricks' joint audio-video family. In mold it is exposed as a separate ltx2 family from the older ltx-video checkpoints, with defaults aimed at synchronized MP4 output and the upstream two-stage / distilled pipelines.

Current status

LTX-2 now runs through mold's in-tree Rust runtime. CUDA is the supported backend for real local generation, CPU is a correctness-oriented fallback, and Metal is explicitly unsupported for this family. The native CUDA workflow matrix is validated across 19B/22B text+audio-video, image-to-video, audio-to-video, keyframe, retake, public IC-LoRA, spatial upscale (x1.5 / x2 where published), and temporal upscale (x2).

Supported Models

Model	Path	Notes
ltx-2-19b-dev:fp8	Two-stage	Highest-quality published 19B FP8 checkpoint
ltx-2-19b-distilled:fp8	Distilled	Fastest 19B path, recommended default
ltx-2.3-22b-dev:fp8	Two-stage	Highest-quality 22B FP8 checkpoint
ltx-2.3-22b-distilled:fp8	Distilled	Fastest 22B path

Implemented Request Surface

• Text-to-audio+video with synchronized MP4 output
• First-frame image-to-video via --image
• Audio-to-video via --audio-file
• Keyframe interpolation via repeatable --keyframe
• Retake / partial regeneration via --video + --retake
• IC-LoRA and stacked LoRAs via repeatable --lora
• Camera-control preset names for the published LTX-2 19B camera LoRAs
• Spatial upscale x2 across the family and x1.5 for ltx-2.3-*
• Temporal upscale x2

Current Constraints

• Default output is mp4 for this family. gif, apng, and webp are also supported, but they are treated as silent exports.
• x2 spatial upscaling is wired across the family. x1.5 is wired for ltx-2.3-* by resolving the published upstream asset on demand.
• x2 temporal upscaling is wired through the native LTX-2 runtime.
• Camera-control preset aliases are currently published for LTX-2 19B only. For LTX-2.3, pass an explicit .safetensors path.
• The Gemma text encoder source is gated on Hugging Face, so you must have access approved before mold pull will complete.
• When you send source media through mold serve, the built-in request body limit is 64 MiB, which covers common inline retake and audio-to-video requests.
• On 24 GB Ada GPUs such as the RTX 4090, mold keeps the native runtime on the compatible fp8-cast path rather than Hopper-only fp8-scaled-mm.

Examples

# Fast default: text to synchronized MP4
mold run ltx-2-19b-distilled:fp8 \
  "cinematic close-up of rain on a neon taxi window" \
  --frames 97 \
  --format mp4

# Audio-to-video
mold run ltx-2-19b-distilled:fp8 \
  "paper cutout forest reacting to a violin solo" \
  --audio-file ./solo.wav \
  --format mp4

# Keyframe interpolation
mold run ltx-2-19b-distilled:fp8 \
  "a drone shot over volcanic cliffs" \
  --pipeline keyframe \
  --frames 97 \
  --keyframe 0:./start.png \
  --keyframe 96:./end.png

# Camera-control preset
mold run ltx-2-19b-distilled:fp8 \
  "a lantern-lit cave entrance" \
  --camera-control dolly-in \
  --format mp4

# Retake a source clip over a time range
mold run ltx-2-19b-distilled:fp8 \
  "replace the actor with a chrome mannequin" \
  --pipeline retake \
  --video ./source.mp4 \
  --retake 1.5:3.5 \
  --format mp4

# Spatial upscale on a published LTX-2.3 asset
mold run ltx-2.3-22b-distilled:fp8 \
  "red sports car in rain, cinematic reflections" \
  --spatial-upscale x1.5 \
  --format mp4

Chained video output

The LTX-2 distilled pipeline maxes out at 97 pixel frames per clip (13 latent frames after the VAE's 8× temporal compression — 8 × 12 + 1 = 97 satisfies the 8k+1 frame-grid constraint). For anything longer, mold renders a chain: the request is split into N sub-clips, each generated back-to-back, and stitched into a single MP4 at the end. mold keeps the last few frames of clip N's final latents in memory and threads them directly into clip N+1's conditioning, skipping a VAE encode/decode round-trip so the continuation stays visually coherent.

mold run routes automatically: when --frames is ≤ 97 you stay on the single-clip path; above 97 the request is rewritten into a chain and dispatched to the new /api/generate/chain/stream endpoint. Chaining is supported for LTX-2 19B and 22B distilled today. Other model families reject --frames > 97 with an actionable error rather than silently over-producing.

$ mold run ltx-2-19b-distilled:fp8 "a cat walking through autumn leaves" \
    --image cat.png --frames 400

→ Chain mode: 400 frames → 5 stages × 97 frames (tail 4)
Chain [━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━] 385/385 frames (stages 5)
  Stage 1  [━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━] 8/8 steps
  Stage 2  [━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━] 8/8 steps
  Stage 3  [━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━] 8/8 steps
  Stage 4  [━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━] 8/8 steps
  Stage 5  [━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━] 8/8 steps
✓ Saved: mold-ltx-2-19b-distilled-<ts>.mp4 (400 frames, 1216x704, 24 fps)
✓ Done — ltx-2-19b-distilled:fp8 in 226.8s (400 frames, seed: 42)

Motion-tail carryover

--motion-tail N (default 4) controls how many trailing pixel frames of each clip are reused as latent-space conditioning for the next. Instead of decoding the prior clip's last frame back to RGB and re-encoding it through the VAE as a new source_image, mold narrows the final denoise tensor along its time axis and patchifies those latent tokens directly into the next stage's StageVideoConditioning — so the handoff never leaves latent space. At stitch time, every stage after the first drops its leading N output frames because those are the overlap region shared with the prior clip.

• --motion-tail 0 — hard concatenation, no overlap. Visible seams are common at clip boundaries; useful when you want discrete shots.
• --motion-tail 4 — the default. One latent frame of carryover at fps=24 gives the transformer enough temporal context to continue motion, object identity, and lighting across the seam without wasting new frames.
• Higher values buy more seam-smoothing at the cost of fewer fresh pixel frames per clip. Must stay strictly below --clip-frames.

Flags

Flag	Default	Description
--frames N	model default	Total stitched length. Above the per-clip cap (97 for LTX-2 distilled), auto-chains.
--clip-frames N	model cap (97)	Per-clip length. Must be 8k+1; values above the cap are clamped with a warning.
--motion-tail N	4	Pixel-frame overlap between clips. 0 disables carryover.

When the final clip over-produces (stage math rarely lands exactly on total_frames), mold trims from the tail so the user-anchored starting image at the head stays intact.

v1 constraints

• LTX-2 19B and 22B distilled only. Other LTX-2 / LTX-Video variants and every image-family model reject --frames above their single-clip budget.
• Single GPU per chain. Every stage runs on the GPU the engine was loaded onto — multi-GPU stage fan-out is a v2 movie-maker feature.
• Fail-closed. If any stage errors, the whole chain returns 502 and nothing is written to the gallery. There is no partial-resume in v1.
• Single prompt per chain from the CLI. The server already accepts per-stage prompts (see POST /api/generate/chain), but mold run replicates one prompt across every stage for now.

The rest of the LTX-2 surface — --image, --audio-file, --lora, --camera-control, --spatial-upscale, --temporal-upscale, and so on — applies to chain renders the same way it applies to single-clip renders. An --image supplied on the CLI lands on stages[0] and is carried forward by the motion-tail latents from there.

Example Clips

Here are a few longer LTX-2 examples rendered with mold. The docs page embeds lightweight webm previews so the examples load quickly in the browser.

ltx-2-19b-distilled:fp8 — 97 frames, 640x384, 12 fps

Storm-lashed lighthouse at dusk, gliding coastal pass, thunder, rain, wind, and surf.

ltx-2-19b-distilled:fp8 — 97 frames, 640x384, 12 fps

Subway-tunnel drummer performance, orbiting concert camera, percussion, reverb, and distant train rumble.

ltx-2.3-22b-distilled:fp8 — 97 frames, 640x384, 12 fps

Red seaplane over an Arctic fjord at sunrise, wingtip bank, spray off the floats, propeller engine, wind, and water hiss.

Notes

• --audio and --no-audio control whether the returned MP4 keeps the audio track. If you explicitly choose gif, apng, or webp, mold exports a silent animation.
• --lora is repeatable for this family. The single legacy lora request field is still populated for backward compatibility, but the LTX-2 runtime uses the stacked loras list.