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jingyu-ml 2e43c80609 [2/4] Diffusion Quantized ckpt export (#810)
## What does this PR do?

**Type of change:** New feature <!-- Use one of the following: Bug fix,
new feature, new example, new tests, documentation. -->

**Overview:** 

This MR adds HuggingFace checkpoint export support for LTX‑2 by treating
TI2VidTwoStagesPipeline as a diffusion-like pipeline, exporting only the
stage‑1 transformer (with QKV-fusion-enabled dummy inputs) and falling
back to writing model.safetensors when save_pretrained isn’t available.
It also preserves the original forward in DynamicModule patching
(_forward_pre_dm) so downstream callers can still invoke the pre-patched
forward implementation.

**Changes**

1. Added the calibration & quantization support of the LTX2, even with
FP8 precision.
2. Preserve original forward before `DynamicModule` patching: when
patching forward, we now stash the pre-patched implementation in
`self._forward_pre_dm` (once) so downstream code can still call the
original forward, then re-bind forward to the class implementation. This
is needed for the LTX2 FP8 calibration.
3. Added LTX‑2 HF export path: `export_hf_checkpoint()` now also treats
ltx_pipelines.ti2vid_two_stages.TI2VidTwoStagesPipeline as a
“diffusion-like” object and routes it through
_export_diffusers_checkpoint() (import guarded; no hard dependency).
4. Generalized component discovery: introduced
get_diffusion_components() (aliasing the old get_diffusers_components)
to support non-diffusers pipelines; for LTX‑2 it returns only
stage_1_transformer.
5. Enabled QKV fusion for LTX‑2 backbone: added a model-aware dummy
forward generator (generate_diffusion_dummy_forward_fn) that builds
minimal LTX Modality inputs (including correct timesteps broadcasting)
so shared-input hooks can run and fuse QKV when applicable.
6. Export fallback for non-save_pretrained modules: when a component
lacks save_pretrained (LTX‑2 transformer), export now writes
model.safetensors + minimal config.json instead of pytorch_model.bin.

Plans

- [x] [1/4] Add the basic functionalities to support limited image
models with NVFP4 + FP8, with some refactoring on the previous LLM code
and the diffusers example. PIC: @jingyu-ml
- [x] [2/4] Add support to more video gen models. PIC: @jingyu-ml 
- [ ] [3/4] Add test cases, refactor on the doc, and all related README.
PIC: @jingyu-ml
- [ ] [4/4] Add the final support to ComfyUI. PIC @jingyu-ml 

## Usage
<!-- You can potentially add a usage example below. -->
```bash
python quantize.py --model ltx-2 --format fp4 --batch-size 64 --calib-size 1 --n-steps 40 --extra-param checkpoint_path=/home/scratch.omniml_data_2/jingyux/models/LTX-2/ltx-2-19b-dev-fp8.safetensors --extra-param distilled_lora_path=/home/scratch.omniml_data_2/jingyux/models/LTX-2/ltx-2-19b-distilled-lora-384.safetensors --extra-param spatial_upsampler_path=/home/scratch.omniml_data_2/jingyux/models/LTX-2/ltx-2-spatial-upscaler-x2-1.0.safetensors --extra-param gemma_root=/home/scratch.omniml_data_2/jingyux/models/LTX-2/gemma-3-12b-it-qat-q4_0-unquantized --extra-param fp8transformer=true --hf-ckpt-dir ./ltx2-nvfp4
```

## Testing
<!-- Mention how have you tested your change if applicable. -->

## Before your PR is "*Ready for review*"
<!-- If you haven't finished some of the above items you can still open
`Draft` PR. -->

- **Make sure you read and follow [Contributor
guidelines](https://github.com/NVIDIA/Model-Optimizer/blob/main/CONTRIBUTING.md)**
and your commits are signed.
- **Is this change backward compatible?**: Yes <!--- If No, explain why.
-->
- **Did you write any new necessary tests?**:No
- **Did you add or update any necessary documentation?**:No
- **Did you update
[Changelog](https://github.com/NVIDIA/Model-Optimizer/blob/main/CHANGELOG.rst)?**:No
<!--- Only for new features, API changes, critical bug fixes or bw
breaking changes. -->

## Additional Information
<!-- E.g. related issue. -->

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

## Release Notes

* **New Features**
* Added LTX-2 video model support with complete quantization and export
pipeline integration
* Introduced `--extra-param` CLI option for flexible model configuration
and parameter passing
* Enhanced export capabilities with broader diffusion model
compatibility

* **Chores**
* Changed default model data type from Half to BFloat16 for improved
numerical stability

<sub>✏️ Tip: You can customize this high-level summary in your review
settings.</sub>

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Signed-off-by: Jingyu Xin <jingyux@nvidia.com>
2026-02-04 10:41:33 +00:00