LTX-2.5 Alpha Gen · VideoOnly NVFP4
One merged checkpoint. A smaller footprint for alpha-matte research.
An experimental 10.04 GB video-only derivative of Lightricks' LTX-2.5 distilled transformer, with Alpha Gen already merged and the resulting weights quantized to NVFP4. Built to explore a more compact path from RGB video to alpha mattes for compositing.
Release status: research candidate. The checkpoint was produced and a small resident smoke test completed, but it failed our strict matte boundary and temporal quality acceptance gates. It is published for inspection, reproduction, and further research, with no claim of production readiness or quality equivalence to the original model.
What is inside
| Property | This checkpoint |
|---|---|
| Base | LTX-2.5 22B distilled transformer |
| Adapter | Official Alpha Gen 0.9 IC-LoRA, merged at strength 1.0 |
| Structure | VideoOnly, 48 transformer blocks |
| Conversion | BF16 source → BF16 Alpha merge → one fresh NVFP4 quantization |
| Activation scale policy | Dynamic |
| File size | 10,044,610,600 bytes: 10.04 GB / 9.35 GiB |
| Quantized matrices | 420; remaining tensors retain their stored precision |
| Scope | Transformer checkpoint only; auxiliary models and runtime are separate |
The audio generation and audio/video coupling paths were structurally removed. This changes the architecture and can change video behavior even when audio output is not requested. Alpha weights were fused before quantization; do not apply the same Alpha LoRA a second time.
Download
hf download mskim8584/LTX-2.5-Alpha-Gen-VideoOnly-NVFP4 \
ltx25-alpha-gen-videoonly48-merged-nvfp4-dynamic.safetensors \
--local-dir ./models/ltx25-alpha
SHA256:
83666b1541b74cb4d5f2c7cdb78054a5d478fcbfa2c30fd224739448bc336365
Runtime and intended workflow
This artifact requires a loader that supports the pruned VideoOnly48 topology and this packed NVFP4 representation with dynamic activation scaling. Compatibility with stock ComfyUI, Diffusers, or the unmodified official pipeline has not been established. The stored configuration metadata originates from the upstream AV model; a loader must explicitly interpret the pruned topology rather than assume the original AV architecture.
The experimental path uses an RGB reference clip and an empty prompt to predict a grayscale alpha matte. It uses cached final empty-prompt conditioning, produced after the upstream feature extractor and connectors. The video VAE and that conditioning asset are not included in this repository; the weight file alone is not a runnable pipeline. NVFP4 storage also does not imply native FP4 arithmetic support on every GPU.
For the original, supported Alpha Gen workflow and auxiliary components, see Lightricks' Alpha Gen model card and LTX-2.5. Those instructions describe the original model, not verified compatibility with this derivative.
What we measured
A single frozen hair smoke case (256 × 160, 9 frames, seed 42) completed on an RTX 5060 Ti with 16 GiB VRAM. The measured peak allocated memory was approximately 10.35 GiB during VAE decode. This is a small-case observation, not a memory guarantee for arbitrary resolutions or clip lengths.
| Metric against the BF16 teacher | Single smoke case |
|---|---|
| Whole-frame MAE | 0.005922 |
| PSNR | 30.81 dB |
| SSIM | 0.97196 |
| Boundary MAE | 0.073130 |
| Temporal boundary MAE | 0.041579 |
| Strict quality acceptance | Failed |
Whole-frame similarity can hide errors concentrated around hair and translucent edges. Temporal measurements use consecutive alpha errors without optical-flow compensation. These figures do not establish generalization, full-model parity, or production quality. No multivideo recovery training is incorporated in this file. Conversion provenance and measured values are available in provenance.json.
Attribution and license
The foundation model and original Alpha Gen adapter were created by Lightricks Ltd. This unofficial derivative was prepared and published by mskim8584. Lightricks has not endorsed this release.
This release remains under the LTX-2.x Community License Agreement. The complete license carried by the checkpoint is reproduced without alteration in LICENSE; the checkpoint's embedded license and metadata are also retained. NOTICE identifies the modifications. All original use restrictions, Section 4, Attachment A, and the incorporated Acceptable Use Policy apply to use and redistribution. The current upstream policy is available here.
Commercial Entities must obtain a separate paid license from Lightricks before any use requiring it under the Agreement. Distribution of this derivative grants no rights beyond that Agreement. Consult the full license for the revenue threshold, non-commercial exceptions, and other conditions.
Upstream: LTX-2.5 · Alpha Gen IC-LoRA · LTX-2 source · Upstream license