FastVideo/LTX-2.3-OmniNFT-LoRA

OmniNFT

Modality-wise Omni Diffusion Negative-aware Fine-Tuning for Joint Audio and Video Generation

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🔈 News

• [2026-05-21] Comfy compatible format is here.
• [2026-05-19] LTX-2.3 has been supported 🚀. LoRA weights for LTX-2.3 are now available!
• [2026-05-13] OmniNFT is released on Arixv.
• [2026-05-11] Code and LoRA weights for LTX-2 are available.

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🏗️ Method Overview

Modality-wise Advantage Routing — Instead of collapsing all rewards into a single global advantage, OmniNFT computes independent per-reward advantages for video, audio, and cross-modal synchronization, then routes each to its responsible generation branch — uni-modal advantages supervise only their own branch while the synchronization advantage is broadcast to both — resolving the advantage inconsistency where roughly half of samples receive opposing rewards across modalities.

Layer-wise Gradient Surgery — To address gradient imbalance where video-branch gradients leak into shallow audio layers dedicated to intra-modal generation, OmniNFT applies a partial stop-gradient on the audio key-value projections in A2V cross-attention at shallow Transformer blocks, suppressing erroneous gradient injection while preserving full gradient flow through the deeper cross-modal alignment layers (AV-Sync Zone).

Region-wise Loss Reweighting — Leveraging V2A cross-attention maps from late denoising steps as an intrinsic proxy for sound-emitting critical regions, OmniNFT aggregates them into per-token importance weights that modulate the video-branch RL loss, providing fine-grained credit assignment that concentrates optimization capacity on regions most critical for audio-video synchronization without requiring external detection modules.

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⚡ Installation

conda create -n omnninft python=3.11
conda activate omnninft
pip install -r requirements.txt

📦 Model Checkpoints

Env Variable	Description	Source
LTX-MODEL	LTX base model	LTX-2 LTX-2.3
OmniNFT_LTX	LTX + OmniNFT	OmniNFT
REWARD_MODELS	All reward models (HPSv3, CLAP, AudioBox, Synchformer, ImageBind, etc.)	OmniNFT-Reward-Series

🚀 Training

Step 0: Download Reward Models

Download all reward model weights from HuggingFace:

huggingface-cli download --resume-download zghhui/OmniNFT-Reward-Series --local-dir Omni_Reward_Series

Reward model checkpoints under Omni_Reward_Series/

Env Variable	Path	Description
HPSV3_CKPT_PATH	Omni_Reward_Series/HPSv3/HPSv3.safetensors	HPSv3 image quality scorer
VIDEOALIGN_CKPT_DIR	Omni_Reward_Series/VideoReward	VideoAlign video quality scorer
AUDIOBOX_CKPT	Omni_Reward_Series/audiobox-aesthetics/checkpoint.pt	AudioBox aesthetics predictor
CLAP_CKPT	Omni_Reward_Series/CLAP	CLAP audio-text alignment model
IMAGEBIND_CKPT	Omni_Reward_Series/ImageBind/imagebind_huge.pth	ImageBind multimodal embeddings
SYNCHFORMER_CKPT	Omni_Reward_Series/synchformer/synchformer_state_dict.pth	Synchformer AV sync scorer

All paths are pre-configured in bash_train_omninft_ltx_fsdp.sh as relative paths.

Step 1: Launch Reward Servers

HPSv3 and VideoAlign run as remote HTTP servers. Start them before training:

# Terminal 1: HPSv3 server
bash flow_grpo/server/run_remote_hpsv3.sh

# Terminal 2: VideoAlign server
bash flow_grpo/server/run_remote_videoalign.sh

Step 2: Multi(Single)-Node Training

bash bash_train_omninft_ltx_fsdp.sh branch_aware_layer_surgery_avweight

🎬 Inference

Step 1: Merge LoRA into base model

After training, merge the LoRA weights into the base checkpoint:

python scripts/merge_lora.py \
    --checkpoint-path $LTX_MODEL_PATH \
    --lora-dir $OUTPUT_DIR/checkpoint-latest/lora \
    --output-path ./merged_model.safetensors \
    --dtype bf16

Arguments

Argument	Description
--checkpoint-path	LTX-Video base checkpoint used during training
--lora-dir	LoRA output directory (contains adapter_model.safetensors + adapter_config.json)
--output-path	Output path for the merged model
--dtype	Output precision: bf16 (default) / fp16 / fp32 / keep

Step 2: Generate audio-video

python scripts/inference.py \
    --model_path ./merged_model.safetensors \
    --gemma_path $GEMMA_MODEL_PATH \
    --prompt "A man plays acoustic guitar on a wooden stage, warm applause from the audience" \
    --seed 42 \
    --output_dir ./results

Arguments

Argument	Default	Description
--model_path	(required)	Path to merged .safetensors model
--gemma_path	env GEMMA_MODEL_PATH	Path to Gemma 3 text encoder
--prompt	(required)	Text prompt for generation
--num_frames	121	Number of video frames
--height / --width	model default	Video resolution
--num_inference_steps	model default	Number of denoising steps
--video_guidance_scale	model default	Video CFG scale
--audio_guidance_scale	model default	Audio CFG scale
--seed	42	Random seed
--no_audio	false	Disable audio generation
--dtype	bf16	Inference precision

Outputs are saved to --output_dir: .mp4 (video with audio) and .wav (audio only).

🖊️ Citation

@article{zhang2026omninft,
  title={OmniNFT: Modality-wise Omni Diffusion Reinforcement for Joint Audio-Video Generation},
  author={Zhang, Guohui and Ma, XiaoXiao and Huang, Jie and Xu, Hang and Yu, Hu and Fu, Siming and Li, Yuming and Xue, Zeyue and Song, Lin and Huang, Haoyang and Duan, Nan and Zhao, Feng},
  journal={arXiv preprint arXiv:2605.12480},
  year={2026}
}

🤝 Acknowledgements

LTX-2 · DiffusionNFT

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⚠️ License

Research use only. See individual submodule licenses (HPSv3, ImageBind, LTX-Video, etc.) for their terms.