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vllm-omni/vllm_omni/diffusion/models/ltx2/pipeline_ltx2_3.py
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2026-04-23 16:51:51 +08:00

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Python

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""
Fully independent LTX-2.3 pipeline for vLLM-Omni.
This pipeline does NOT inherit from LTX2Pipeline because:
- LTX-2.3 uses a different text encoding strategy (flatten ALL 49 hidden states
vs. LTX-2's _pack_text_embeds with per-layer normalization and pooling)
- LTX-2.3 connectors expect the padding_side API (not additive_mask)
- LTX-2.3 uses a BWE vocoder outputting 48kHz audio (not 16kHz)
- LTX-2.3 transformer requires the sigma parameter for prompt modulation
- CPU offloading is required for the 22B transformer (~44GB VRAM)
"""
from __future__ import annotations
import copy
import json
import os
from collections.abc import Iterable
from contextlib import nullcontext
from typing import Any
import numpy as np
import torch
from diffusers import AutoencoderKLLTX2Audio, AutoencoderKLLTX2Video, FlowMatchEulerDiscreteScheduler
from diffusers.pipelines.ltx2 import LTX2TextConnectors
from diffusers.pipelines.ltx2.vocoder import LTX2Vocoder
from diffusers.pipelines.stable_diffusion.pipeline_stable_diffusion import retrieve_timesteps
from diffusers.utils.torch_utils import randn_tensor
from diffusers.video_processor import VideoProcessor
from huggingface_hub import hf_hub_download
from torch import nn
from transformers import AutoTokenizer, Gemma3ForConditionalGeneration
from vllm.logger import init_logger
from vllm.model_executor.models.utils import AutoWeightsLoader
from vllm_omni.diffusion.data import DiffusionOutput, OmniDiffusionConfig
from vllm_omni.diffusion.distributed.utils import get_local_device
from vllm_omni.diffusion.model_loader.diffusers_loader import DiffusersPipelineLoader
from vllm_omni.diffusion.models.progress_bar import ProgressBarMixin
from vllm_omni.diffusion.request import OmniDiffusionRequest
from .pipeline_ltx2 import (
_get_prompt_field,
calculate_shift,
create_transformer_from_config,
load_transformer_config,
)
logger = init_logger(__name__)
# Try to import LTX2VocoderWithBWE (diffusers >= 0.38.0)
try:
from diffusers.pipelines.ltx2.vocoder import LTX2VocoderWithBWE
except ImportError:
LTX2VocoderWithBWE = None
def _detect_vocoder_output_sample_rate(model: str) -> int | None:
"""Detect the vocoder output sample rate from vocoder/config.json.
This runs at factory time (engine process) so the rate is captured in
the post-process closure and doesn't need cross-process communication.
Returns:
Output sample rate (e.g. 48000 for LTX-2.3 BWE vocoder) or None.
"""
vocoder_config_path = os.path.join(model, "vocoder", "config.json")
if not os.path.exists(vocoder_config_path):
try:
vocoder_config_path = hf_hub_download(model, "vocoder/config.json")
except Exception:
return None
try:
with open(vocoder_config_path) as f:
cfg = json.load(f)
return cfg.get("output_sampling_rate")
except Exception:
return None
def get_ltx2_post_process_func(od_config: OmniDiffusionConfig):
"""Factory for the LTX-2.3 post-process function.
Detects the vocoder output sample rate at factory time and captures it
in the closure so that the audio_sample_rate flows through
DiffusionEngine -> OmniRequestOutput -> serving_video.
"""
output_sr = _detect_vocoder_output_sample_rate(od_config.model)
def post_process_func(output: tuple[torch.Tensor, torch.Tensor] | torch.Tensor):
if isinstance(output, tuple) and len(output) == 2:
video, audio = output
if isinstance(audio, torch.Tensor):
audio = audio.detach().cpu()
result: dict[str, Any] = {"video": video, "audio": audio}
if output_sr is not None:
result["audio_sample_rate"] = output_sr
return result
return output
return post_process_func
class LTX23Pipeline(nn.Module, ProgressBarMixin):
"""Fully independent LTX-2.3 pipeline.
Key differences from LTX2Pipeline:
- Text encoding: uses ALL 49 hidden states from Gemma-3-12B, flattened
- Connectors: uses padding_side API (not additive_mask)
- Vocoder: uses LTX2VocoderWithBWE (48kHz output)
- Transformer: passes sigma for prompt_adaln
- CPU offloading: text encoder, connectors, VAE, vocoder stay on CPU
"""
def __init__(
self,
*,
od_config: OmniDiffusionConfig,
prefix: str = "",
):
super().__init__()
self.od_config = od_config
self.device = get_local_device()
dtype = getattr(od_config, "dtype", torch.bfloat16)
model = od_config.model
local_files_only = os.path.exists(model)
# Weight sources for transformer (loaded via AutoWeightsLoader)
self.weights_sources = [
DiffusersPipelineLoader.ComponentSource(
model_or_path=od_config.model,
subfolder="transformer",
revision=None,
prefix="transformer.",
fall_back_to_pt=True,
),
]
# --- Tokenizer (lightweight, stays wherever) ---
self.tokenizer = AutoTokenizer.from_pretrained(model, subfolder="tokenizer", local_files_only=local_files_only)
# --- Text encoder: load on CPU, move to GPU only during encoding ---
with torch.device("cpu"):
self.text_encoder = Gemma3ForConditionalGeneration.from_pretrained(
model, subfolder="text_encoder", torch_dtype=dtype, local_files_only=local_files_only
)
# --- Connectors: CPU (LTX-2.3 connectors include caption projection) ---
self.connectors = LTX2TextConnectors.from_pretrained(
model, subfolder="connectors", torch_dtype=dtype, local_files_only=local_files_only
)
# --- VAE, Audio VAE: CPU ---
self.vae = AutoencoderKLLTX2Video.from_pretrained(
model, subfolder="vae", torch_dtype=dtype, local_files_only=local_files_only
)
self.audio_vae = AutoencoderKLLTX2Audio.from_pretrained(
model, subfolder="audio_vae", torch_dtype=dtype, local_files_only=local_files_only
)
# --- Vocoder: prefer BWE vocoder (48kHz) for LTX-2.3 ---
vocoder_cls = LTX2VocoderWithBWE or LTX2Vocoder
try:
self.vocoder = vocoder_cls.from_pretrained(
model, subfolder="vocoder", torch_dtype=dtype, local_files_only=local_files_only
)
except (TypeError, OSError, ValueError):
self.vocoder = LTX2Vocoder.from_pretrained(
model, subfolder="vocoder", torch_dtype=dtype, local_files_only=local_files_only
)
# --- Transformer: created empty, weights loaded via AutoWeightsLoader ---
transformer_config = load_transformer_config(model, "transformer", local_files_only)
self.transformer = create_transformer_from_config(transformer_config)
# --- Scheduler ---
self.scheduler = FlowMatchEulerDiscreteScheduler.from_pretrained(
model, subfolder="scheduler", local_files_only=local_files_only
)
# --- Derived compression ratios ---
self.vae_spatial_compression_ratio = self.vae.spatial_compression_ratio if self.vae is not None else 32
self.vae_temporal_compression_ratio = self.vae.temporal_compression_ratio if self.vae is not None else 8
self.audio_vae_mel_compression_ratio = self.audio_vae.mel_compression_ratio if self.audio_vae is not None else 4
self.audio_vae_temporal_compression_ratio = (
self.audio_vae.temporal_compression_ratio if self.audio_vae is not None else 4
)
self.transformer_spatial_patch_size = self.transformer.config.patch_size if self.transformer is not None else 1
self.transformer_temporal_patch_size = (
self.transformer.config.patch_size_t if self.transformer is not None else 1
)
self.audio_sampling_rate = self.audio_vae.config.sample_rate if self.audio_vae is not None else 16000
self.audio_hop_length = self.audio_vae.config.mel_hop_length if self.audio_vae is not None else 160
self.video_processor = VideoProcessor(vae_scale_factor=self.vae_spatial_compression_ratio)
# Tokenizer max length
tokenizer_max_length = 1024
if self.tokenizer is not None:
tokenizer_max_length = self.tokenizer.model_max_length
if tokenizer_max_length is None or tokenizer_max_length > 100000:
encoder_config = getattr(self.text_encoder, "config", None)
config_max_len = getattr(encoder_config, "max_position_embeddings", None)
if config_max_len is None:
config_max_len = getattr(encoder_config, "max_seq_len", None)
tokenizer_max_length = config_max_len or 1024
self.tokenizer_max_length = int(tokenizer_max_length)
# Pipeline state
self._guidance_scale = None
self._attention_kwargs = None
self._interrupt = False
self._num_timesteps = None
self._current_timestep = None
# ------------------------------------------------------------------
# Text Encoding (LTX-2.3 specific)
# ------------------------------------------------------------------
def _get_gemma_prompt_embeds(
self,
prompt: str | list[str],
num_videos_per_prompt: int = 1,
max_sequence_length: int = 1024,
device: torch.device | None = None,
dtype: torch.dtype | None = None,
):
"""Encode prompts using Gemma-3-12B, returning ALL 49 hidden states flattened.
LTX-2.3 differs from LTX-2 in text encoding:
- LTX-2: uses _pack_text_embeds (layer selection + pooling)
- LTX-2.3: stacks ALL 49 hidden states and flattens to [B, seq, 188160]
The connectors unflatten, apply per_token_rms_norm, and project internally.
"""
device = device or self.device
dtype = dtype or self.text_encoder.dtype
prompt = [prompt] if isinstance(prompt, str) else prompt
batch_size = len(prompt)
if self.tokenizer is not None:
self.tokenizer.padding_side = "left"
if self.tokenizer.pad_token is None:
self.tokenizer.pad_token = self.tokenizer.eos_token
prompt = [p.strip() for p in prompt]
text_inputs = self.tokenizer(
prompt,
padding="max_length",
max_length=max_sequence_length,
truncation=True,
add_special_tokens=True,
return_tensors="pt",
)
text_input_ids = text_inputs.input_ids.to(device)
prompt_attention_mask = text_inputs.attention_mask.to(device)
# Move text encoder to GPU for encoding
self.text_encoder.to(device)
text_encoder_outputs = self.text_encoder(
input_ids=text_input_ids,
attention_mask=prompt_attention_mask,
output_hidden_states=True,
)
# Move text encoder back to CPU immediately
self.text_encoder.to("cpu")
torch.cuda.empty_cache()
hidden_states = text_encoder_outputs.hidden_states
# LTX-2.3: Stack ALL 49 hidden states and flatten
# [49 x (B, seq, 3840)] -> [B, seq, 3840, 49] -> [B, seq, 188160]
prompt_embeds = torch.stack(hidden_states, dim=-1).flatten(2, 3).to(dtype=dtype)
_, seq_len, _ = prompt_embeds.shape
prompt_embeds = prompt_embeds.repeat(1, num_videos_per_prompt, 1)
prompt_embeds = prompt_embeds.view(batch_size * num_videos_per_prompt, seq_len, -1)
prompt_attention_mask = prompt_attention_mask.view(batch_size, -1)
prompt_attention_mask = prompt_attention_mask.repeat(num_videos_per_prompt, 1)
return prompt_embeds, prompt_attention_mask
def encode_prompt(
self,
prompt: str | list[str],
negative_prompt: str | list[str] | None = None,
do_classifier_free_guidance: bool = True,
num_videos_per_prompt: int = 1,
prompt_embeds: torch.Tensor | None = None,
negative_prompt_embeds: torch.Tensor | None = None,
prompt_attention_mask: torch.Tensor | None = None,
negative_prompt_attention_mask: torch.Tensor | None = None,
max_sequence_length: int = 1024,
device: torch.device | None = None,
dtype: torch.dtype | None = None,
):
device = device or self.device
prompt = [prompt] if isinstance(prompt, str) else prompt
if prompt is not None:
batch_size = len(prompt)
else:
batch_size = prompt_embeds.shape[0]
if prompt_embeds is None:
prompt_embeds, prompt_attention_mask = self._get_gemma_prompt_embeds(
prompt=prompt,
num_videos_per_prompt=num_videos_per_prompt,
max_sequence_length=max_sequence_length,
device=device,
dtype=dtype,
)
if do_classifier_free_guidance and negative_prompt_embeds is None:
negative_prompt = negative_prompt or ""
negative_prompt = batch_size * [negative_prompt] if isinstance(negative_prompt, str) else negative_prompt
if prompt is not None and type(prompt) is not type(negative_prompt):
raise TypeError(
f"`negative_prompt` should be the same type as `prompt`, but got {type(negative_prompt)} !="
f" {type(prompt)}."
)
if isinstance(negative_prompt, list) and batch_size != len(negative_prompt):
raise ValueError(
f"`negative_prompt`: {negative_prompt} has batch size {len(negative_prompt)}, but `prompt`:"
f" {prompt} has batch size {batch_size}. Please make sure that passed `negative_prompt` matches"
" the batch size of `prompt`."
)
negative_prompt_embeds, negative_prompt_attention_mask = self._get_gemma_prompt_embeds(
prompt=negative_prompt,
num_videos_per_prompt=num_videos_per_prompt,
max_sequence_length=max_sequence_length,
device=device,
dtype=dtype,
)
return prompt_embeds, prompt_attention_mask, negative_prompt_embeds, negative_prompt_attention_mask
# ------------------------------------------------------------------
# Latent utilities (shared with LTX2Pipeline)
# ------------------------------------------------------------------
@staticmethod
def _pack_latents(latents: torch.Tensor, patch_size: int = 1, patch_size_t: int = 1) -> torch.Tensor:
batch_size, num_channels, num_frames, height, width = latents.shape
post_patch_num_frames = num_frames // patch_size_t
post_patch_height = height // patch_size
post_patch_width = width // patch_size
latents = latents.reshape(
batch_size,
-1,
post_patch_num_frames,
patch_size_t,
post_patch_height,
patch_size,
post_patch_width,
patch_size,
)
latents = latents.permute(0, 2, 4, 6, 1, 3, 5, 7).flatten(4, 7).flatten(1, 3)
return latents
@staticmethod
def _unpack_latents(
latents: torch.Tensor,
num_frames: int,
height: int,
width: int,
patch_size: int = 1,
patch_size_t: int = 1,
) -> torch.Tensor:
batch_size = latents.size(0)
latents = latents.reshape(batch_size, num_frames, height, width, -1, patch_size_t, patch_size, patch_size)
latents = latents.permute(0, 4, 1, 5, 2, 6, 3, 7).flatten(6, 7).flatten(4, 5).flatten(2, 3)
return latents
@staticmethod
def _normalize_latents(
latents: torch.Tensor, latents_mean: torch.Tensor, latents_std: torch.Tensor, scaling_factor: float = 1.0
) -> torch.Tensor:
latents_mean = latents_mean.view(1, -1, 1, 1, 1).to(latents.device, latents.dtype)
latents_std = latents_std.view(1, -1, 1, 1, 1).to(latents.device, latents.dtype)
latents = (latents - latents_mean) * scaling_factor / latents_std
return latents
@staticmethod
def _normalize_audio_latents(latents: torch.Tensor, latents_mean: torch.Tensor, latents_std: torch.Tensor):
latents_mean = latents_mean.to(latents.device, latents.dtype)
latents_std = latents_std.to(latents.device, latents.dtype)
return (latents - latents_mean) / latents_std
@staticmethod
def _denormalize_latents(
latents: torch.Tensor, latents_mean: torch.Tensor, latents_std: torch.Tensor, scaling_factor: float = 1.0
) -> torch.Tensor:
latents_mean = latents_mean.view(1, -1, 1, 1, 1).to(latents.device, latents.dtype)
latents_std = latents_std.view(1, -1, 1, 1, 1).to(latents.device, latents.dtype)
latents = latents * latents_std / scaling_factor + latents_mean
return latents
@staticmethod
def _denormalize_audio_latents(latents: torch.Tensor, latents_mean: torch.Tensor, latents_std: torch.Tensor):
latents_mean = latents_mean.to(latents.device, latents.dtype)
latents_std = latents_std.to(latents.device, latents.dtype)
return (latents * latents_std) + latents_mean
@staticmethod
def _pack_audio_latents(
latents: torch.Tensor, patch_size: int | None = None, patch_size_t: int | None = None
) -> torch.Tensor:
if patch_size is not None and patch_size_t is not None:
batch_size, num_channels, latent_length, latent_mel_bins = latents.shape
post_patch_latent_length = latent_length / patch_size_t
post_patch_mel_bins = latent_mel_bins / patch_size
latents = latents.reshape(
batch_size, -1, post_patch_latent_length, patch_size_t, post_patch_mel_bins, patch_size
)
latents = latents.permute(0, 2, 4, 1, 3, 5).flatten(3, 5).flatten(1, 2)
else:
latents = latents.transpose(1, 2).flatten(2, 3)
return latents
@staticmethod
def _unpack_audio_latents(
latents: torch.Tensor,
latent_length: int,
num_mel_bins: int,
patch_size: int | None = None,
patch_size_t: int | None = None,
) -> torch.Tensor:
if patch_size is not None and patch_size_t is not None:
batch_size = latents.size(0)
latents = latents.reshape(batch_size, latent_length, num_mel_bins, -1, patch_size_t, patch_size)
latents = latents.permute(0, 3, 1, 4, 2, 5).flatten(4, 5).flatten(2, 3)
else:
latents = latents.unflatten(2, (-1, num_mel_bins)).transpose(1, 2)
return latents
@staticmethod
def _unpad_audio_latents(latents: torch.Tensor, num_frames: int) -> torch.Tensor:
return latents[:, :num_frames]
# ------------------------------------------------------------------
# Latent preparation
# ------------------------------------------------------------------
def prepare_latents(
self,
batch_size: int = 1,
num_channels_latents: int = 128,
height: int = 512,
width: int = 768,
num_frames: int = 121,
noise_scale: float = 0.0,
dtype: torch.dtype | None = None,
device: torch.device | None = None,
generator: torch.Generator | None = None,
latents: torch.Tensor | None = None,
) -> torch.Tensor:
if latents is not None:
if latents.ndim == 5:
latents = self._normalize_latents(
latents, self.vae.latents_mean, self.vae.latents_std, self.vae.config.scaling_factor
)
latents = self._pack_latents(
latents, self.transformer_spatial_patch_size, self.transformer_temporal_patch_size
)
if latents.ndim != 3:
raise ValueError(f"Provided `latents` has shape {latents.shape}, expected [batch, seq, features].")
noise = randn_tensor(latents.shape, generator=generator, device=latents.device, dtype=latents.dtype)
latents = noise_scale * noise + (1 - noise_scale) * latents
return latents.to(device=device, dtype=dtype)
height = height // self.vae_spatial_compression_ratio
width = width // self.vae_spatial_compression_ratio
num_frames = (num_frames - 1) // self.vae_temporal_compression_ratio + 1
shape = (batch_size, num_channels_latents, num_frames, height, width)
latents = randn_tensor(shape, generator=generator, device=device, dtype=dtype)
latents = self._pack_latents(latents, self.transformer_spatial_patch_size, self.transformer_temporal_patch_size)
return latents
def prepare_audio_latents(
self,
batch_size: int = 1,
num_channels_latents: int = 8,
audio_latent_length: int = 1,
num_mel_bins: int = 64,
noise_scale: float = 0.0,
dtype: torch.dtype | None = None,
device: torch.device | None = None,
generator: torch.Generator | list[torch.Generator] | None = None,
latents: torch.Tensor | None = None,
) -> tuple[torch.Tensor, int, int]:
original_latent_length = audio_latent_length
padded_latent_length = original_latent_length
latent_mel_bins = num_mel_bins // self.audio_vae_mel_compression_ratio
if latents is not None:
if latents.ndim == 4:
latents = self._pack_audio_latents(latents)
if latents.ndim != 3:
raise ValueError(f"Provided `latents` has shape {latents.shape}, expected [batch, seq, features].")
latents = self._normalize_audio_latents(latents, self.audio_vae.latents_mean, self.audio_vae.latents_std)
noise = randn_tensor(latents.shape, generator=generator, device=latents.device, dtype=latents.dtype)
latents = noise_scale * noise + (1 - noise_scale) * latents
return latents.to(device=device, dtype=dtype), original_latent_length, padded_latent_length
shape = (batch_size, num_channels_latents, padded_latent_length, latent_mel_bins)
latents = randn_tensor(shape, generator=generator, device=device, dtype=dtype)
latents = self._pack_audio_latents(latents)
return latents, original_latent_length, padded_latent_length
# ------------------------------------------------------------------
# Properties
# ------------------------------------------------------------------
@property
def guidance_scale(self):
return self._guidance_scale
@property
def do_classifier_free_guidance(self):
return self._guidance_scale is not None and self._guidance_scale > 1.0
@property
def num_timesteps(self):
return self._num_timesteps
@property
def current_timestep(self):
return self._current_timestep
@property
def interrupt(self):
return self._interrupt
# ------------------------------------------------------------------
# Input validation
# ------------------------------------------------------------------
def check_inputs(
self,
prompt,
height,
width,
prompt_embeds=None,
negative_prompt_embeds=None,
prompt_attention_mask=None,
negative_prompt_attention_mask=None,
):
if height % 32 != 0 or width % 32 != 0:
raise ValueError(f"`height` and `width` must be divisible by 32 but are {height} and {width}.")
if prompt is not None and prompt_embeds is not None:
raise ValueError("Cannot forward both `prompt` and `prompt_embeds`.")
elif prompt is None and prompt_embeds is None:
raise ValueError("Provide either `prompt` or `prompt_embeds`.")
elif prompt is not None and not isinstance(prompt, (str, list)):
raise ValueError(f"`prompt` has to be of type `str` or `list` but is {type(prompt)}")
if prompt_embeds is not None and prompt_attention_mask is None:
raise ValueError("Must provide `prompt_attention_mask` when specifying `prompt_embeds`.")
if negative_prompt_embeds is not None and negative_prompt_attention_mask is None:
raise ValueError("Must provide `negative_prompt_attention_mask` when specifying `negative_prompt_embeds`.")
if prompt_embeds is not None and negative_prompt_embeds is not None:
if prompt_embeds.shape != negative_prompt_embeds.shape:
raise ValueError(
"`prompt_embeds` and `negative_prompt_embeds` must have the same shape when passed directly, but"
f" got: `prompt_embeds` {prompt_embeds.shape} != `negative_prompt_embeds`"
f" {negative_prompt_embeds.shape}."
)
if prompt_attention_mask.shape != negative_prompt_attention_mask.shape:
raise ValueError(
"`prompt_attention_mask` and `negative_prompt_attention_mask` must have the same shape when "
"passed directly, but got: `prompt_attention_mask` "
f"{prompt_attention_mask.shape} != `negative_prompt_attention_mask` "
f"{negative_prompt_attention_mask.shape}."
)
# ------------------------------------------------------------------
# Cache context
# ------------------------------------------------------------------
def _transformer_cache_context(self, context_name: str):
cache_context = getattr(self.transformer, "cache_context", None)
if callable(cache_context):
return cache_context(context_name)
return nullcontext()
# ------------------------------------------------------------------
# Forward pass
# ------------------------------------------------------------------
@torch.no_grad()
def forward(
self,
req: OmniDiffusionRequest,
prompt: str | list[str] | None = None,
negative_prompt: str | list[str] | None = None,
height: int | None = None,
width: int | None = None,
num_frames: int | None = None,
frame_rate: float | None = None,
num_inference_steps: int | None = None,
sigmas: list[float] | None = None,
timesteps: list[int] | None = None,
guidance_scale: float = 4.0,
noise_scale: float = 0.0,
num_videos_per_prompt: int | None = 1,
generator: torch.Generator | list[torch.Generator] | None = None,
latents: torch.Tensor | None = None,
audio_latents: torch.Tensor | None = None,
prompt_embeds: torch.Tensor | None = None,
negative_prompt_embeds: torch.Tensor | None = None,
prompt_attention_mask: torch.Tensor | None = None,
negative_prompt_attention_mask: torch.Tensor | None = None,
decode_timestep: float | list[float] = 0.0,
decode_noise_scale: float | list[float] | None = None,
output_type: str = "np",
return_dict: bool = True,
attention_kwargs: dict[str, Any] | None = None,
max_sequence_length: int | None = None,
) -> DiffusionOutput:
# ---- Extract from request ----
prompt = [p if isinstance(p, str) else (p.get("prompt") or "") for p in req.prompts] or prompt
if all(isinstance(p, str) or p.get("negative_prompt") is None for p in req.prompts):
negative_prompt = None
elif req.prompts:
negative_prompt = ["" if isinstance(p, str) else (p.get("negative_prompt") or "") for p in req.prompts]
height = req.sampling_params.height or height or 512
width = req.sampling_params.width or width or 768
num_frames = req.sampling_params.num_frames or num_frames or 121
frame_rate = req.sampling_params.resolved_frame_rate or frame_rate or 24.0
num_inference_steps = req.sampling_params.num_inference_steps or num_inference_steps or 40
# Enforce minimum of 2 timesteps for flow matching scheduler
if timesteps is None:
num_inference_steps = max(int(num_inference_steps), 2)
elif len(timesteps) < 2:
raise ValueError("`timesteps` must contain at least 2 values for FlowMatchEulerDiscreteScheduler.")
num_videos_per_prompt = (
req.sampling_params.num_outputs_per_prompt
if req.sampling_params.num_outputs_per_prompt > 0
else num_videos_per_prompt or 1
)
max_sequence_length = (
req.sampling_params.max_sequence_length or max_sequence_length or self.tokenizer_max_length
)
if req.sampling_params.guidance_scale_provided:
guidance_scale = req.sampling_params.guidance_scale
if generator is None:
generator = req.sampling_params.generator
if generator is None and req.sampling_params.seed is not None:
generator = torch.Generator(device=self.device).manual_seed(req.sampling_params.seed)
latents = req.sampling_params.latents if req.sampling_params.latents is not None else latents
audio_latents = (
req.sampling_params.audio_latents
if req.sampling_params.audio_latents is not None
else req.sampling_params.extra_args.get("audio_latents", audio_latents)
)
# Override with pre-computed embeddings if provided in request
req_prompt_embeds = [_get_prompt_field(p, "prompt_embeds") for p in req.prompts]
if any(p is not None for p in req_prompt_embeds):
prompt_embeds = torch.stack(req_prompt_embeds)
req_negative_prompt_embeds = [_get_prompt_field(p, "negative_prompt_embeds") for p in req.prompts]
if any(p is not None for p in req_negative_prompt_embeds):
negative_prompt_embeds = torch.stack(req_negative_prompt_embeds)
req_prompt_attention_masks = [
_get_prompt_field(p, "prompt_attention_mask") or _get_prompt_field(p, "attention_mask") for p in req.prompts
]
if any(m is not None for m in req_prompt_attention_masks):
prompt_attention_mask = torch.stack(req_prompt_attention_masks)
req_negative_attention_masks = [
_get_prompt_field(p, "negative_prompt_attention_mask") or _get_prompt_field(p, "negative_attention_mask")
for p in req.prompts
]
if any(m is not None for m in req_negative_attention_masks):
negative_prompt_attention_mask = torch.stack(req_negative_attention_masks)
if req.sampling_params.decode_timestep is not None:
decode_timestep = req.sampling_params.decode_timestep
if req.sampling_params.decode_noise_scale is not None:
decode_noise_scale = req.sampling_params.decode_noise_scale
if req.sampling_params.output_type is not None:
output_type = req.sampling_params.output_type
self.check_inputs(
prompt=prompt,
height=height,
width=width,
prompt_embeds=prompt_embeds,
negative_prompt_embeds=negative_prompt_embeds,
prompt_attention_mask=prompt_attention_mask,
negative_prompt_attention_mask=negative_prompt_attention_mask,
)
self._guidance_scale = guidance_scale
self._attention_kwargs = attention_kwargs
self._interrupt = False
self._current_timestep = None
if prompt is not None and isinstance(prompt, str):
batch_size = 1
elif prompt is not None and isinstance(prompt, list):
batch_size = len(prompt)
else:
batch_size = prompt_embeds.shape[0]
device = self.device
# ---- Encode prompts ----
(
prompt_embeds,
prompt_attention_mask,
negative_prompt_embeds,
negative_prompt_attention_mask,
) = self.encode_prompt(
prompt=prompt,
negative_prompt=negative_prompt,
do_classifier_free_guidance=self.do_classifier_free_guidance,
num_videos_per_prompt=num_videos_per_prompt,
prompt_embeds=prompt_embeds,
negative_prompt_embeds=negative_prompt_embeds,
prompt_attention_mask=prompt_attention_mask,
negative_prompt_attention_mask=negative_prompt_attention_mask,
max_sequence_length=max_sequence_length,
device=device,
)
# ---- Connectors (LTX-2.3: padding_side API) ----
# Concatenate negative + positive embeddings BEFORE connector call,
# matching diffusers which calls connectors once with batch=2.
# This ensures batch-dependent operations produce identical results.
if self.do_classifier_free_guidance:
prompt_embeds = torch.cat([negative_prompt_embeds, prompt_embeds], dim=0)
prompt_attention_mask = torch.cat([negative_prompt_attention_mask, prompt_attention_mask], dim=0)
self.connectors.to(device)
tokenizer_padding_side = getattr(self.tokenizer, "padding_side", "left")
connector_prompt_embeds, connector_audio_prompt_embeds, connector_attention_mask = self.connectors(
prompt_embeds, prompt_attention_mask, padding_side=tokenizer_padding_side
)
self.connectors.to("cpu")
if torch.cuda.is_available():
torch.cuda.empty_cache()
# ---- Prepare latents ----
latent_num_frames = (num_frames - 1) // self.vae_temporal_compression_ratio + 1
latent_height = height // self.vae_spatial_compression_ratio
latent_width = width // self.vae_spatial_compression_ratio
if latents is not None and latents.ndim == 5:
_, _, latent_num_frames, latent_height, latent_width = latents.shape
num_channels_latents = self.transformer.config.in_channels
latents = self.prepare_latents(
batch_size * num_videos_per_prompt,
num_channels_latents,
height,
width,
num_frames,
noise_scale,
torch.float32,
device,
generator,
latents,
)
duration_s = num_frames / frame_rate
audio_latents_per_second = (
self.audio_sampling_rate / self.audio_hop_length / float(self.audio_vae_temporal_compression_ratio)
)
audio_num_frames = round(duration_s * audio_latents_per_second)
if audio_latents is not None and audio_latents.ndim == 4:
_, _, audio_num_frames, _ = audio_latents.shape
num_mel_bins = self.audio_vae.config.mel_bins if self.audio_vae is not None else 64
latent_mel_bins = num_mel_bins // self.audio_vae_mel_compression_ratio
num_channels_latents_audio = self.audio_vae.config.latent_channels if self.audio_vae is not None else 8
audio_latents, original_audio_num_frames, padded_audio_num_frames = self.prepare_audio_latents(
batch_size * num_videos_per_prompt,
num_channels_latents=num_channels_latents_audio,
audio_latent_length=audio_num_frames,
num_mel_bins=num_mel_bins,
noise_scale=noise_scale,
dtype=torch.float32,
device=device,
generator=generator,
latents=audio_latents,
)
# ---- Scheduler setup ----
sigmas = np.linspace(1.0, 1 / num_inference_steps, num_inference_steps) if sigmas is None else sigmas
# Use max_image_seq_len (not actual video_sequence_length) for mu calculation,
# matching diffusers' LTX2Pipeline which hardcodes this value.
mu = calculate_shift(
self.scheduler.config.get("max_image_seq_len", 4096),
self.scheduler.config.get("base_image_seq_len", 1024),
self.scheduler.config.get("max_image_seq_len", 4096),
self.scheduler.config.get("base_shift", 0.95),
self.scheduler.config.get("max_shift", 2.05),
)
audio_scheduler = copy.deepcopy(self.scheduler)
_ = retrieve_timesteps(audio_scheduler, num_inference_steps, device, timesteps, sigmas=sigmas, mu=mu)
timesteps, num_inference_steps = retrieve_timesteps(
self.scheduler,
num_inference_steps,
device,
timesteps,
sigmas=sigmas,
mu=mu,
)
self._num_timesteps = len(timesteps)
# ---- RoPE coordinates ----
video_coords = self.transformer.rope.prepare_video_coords(
latents.shape[0],
latent_num_frames,
latent_height,
latent_width,
latents.device,
fps=frame_rate,
)
audio_coords = self.transformer.audio_rope.prepare_audio_coords(
audio_latents.shape[0],
padded_audio_num_frames,
audio_latents.device,
)
# ---- CFG: duplicate coords for batch=2 ----
# Connector outputs are already batch=2 (neg+pos concatenated before connector call)
if self.do_classifier_free_guidance:
video_coords = video_coords.repeat((2,) + (1,) * (video_coords.ndim - 1))
audio_coords = audio_coords.repeat((2,) + (1,) * (audio_coords.ndim - 1))
# ---- Denoising loop ----
# Uses x0-space CFG (delta formulation) matching diffusers' LTX2Pipeline.
# The velocity predictions are converted to x0, guidance is applied in x0
# space, then converted back to velocity for the scheduler step.
with self.progress_bar(total=len(timesteps)) as pbar:
for i, t in enumerate(timesteps):
if self.interrupt:
continue
self._current_timestep = t
# Duplicate latents for CFG (uncond + cond)
latent_model_input = torch.cat([latents] * 2) if self.do_classifier_free_guidance else latents
latent_model_input = latent_model_input.to(connector_prompt_embeds.dtype)
audio_latent_model_input = (
torch.cat([audio_latents] * 2) if self.do_classifier_free_guidance else audio_latents
)
audio_latent_model_input = audio_latent_model_input.to(connector_prompt_embeds.dtype)
ts = t.expand(latent_model_input.shape[0])
with self._transformer_cache_context("cond_uncond"):
noise_pred_video, noise_pred_audio = self.transformer(
hidden_states=latent_model_input,
audio_hidden_states=audio_latent_model_input,
encoder_hidden_states=connector_prompt_embeds,
audio_encoder_hidden_states=connector_audio_prompt_embeds,
timestep=ts,
sigma=ts, # LTX-2.3: sigma for prompt_adaln
encoder_attention_mask=connector_attention_mask,
audio_encoder_attention_mask=connector_attention_mask,
num_frames=latent_num_frames,
height=latent_height,
width=latent_width,
fps=frame_rate,
audio_num_frames=padded_audio_num_frames,
video_coords=video_coords,
audio_coords=audio_coords,
attention_kwargs=attention_kwargs,
return_dict=False,
)
noise_pred_video = noise_pred_video.float()
noise_pred_audio = noise_pred_audio.float()
# CFG in x0-space (delta formulation matching diffusers)
if self.do_classifier_free_guidance:
noise_pred_video_uncond, noise_pred_video_cond = noise_pred_video.chunk(2)
# Convert velocity to x0: x0 = sample - velocity * sigma
x0_video_cond = latents - noise_pred_video_cond * self.scheduler.sigmas[i]
x0_video_uncond = latents - noise_pred_video_uncond * self.scheduler.sigmas[i]
video_cfg_delta = (guidance_scale - 1) * (x0_video_cond - x0_video_uncond)
x0_video_guided = x0_video_cond + video_cfg_delta
noise_pred_audio_uncond, noise_pred_audio_cond = noise_pred_audio.chunk(2)
x0_audio_cond = audio_latents - noise_pred_audio_cond * audio_scheduler.sigmas[i]
x0_audio_uncond = audio_latents - noise_pred_audio_uncond * audio_scheduler.sigmas[i]
audio_cfg_delta = (guidance_scale - 1) * (x0_audio_cond - x0_audio_uncond)
x0_audio_guided = x0_audio_cond + audio_cfg_delta
# Convert x0 back to velocity: v = (sample - x0) / sigma
noise_pred_video = (latents - x0_video_guided) / self.scheduler.sigmas[i]
noise_pred_audio = (audio_latents - x0_audio_guided) / audio_scheduler.sigmas[i]
latents = self.scheduler.step(noise_pred_video, t, latents, return_dict=False)[0]
audio_latents = audio_scheduler.step(noise_pred_audio, t, audio_latents, return_dict=False)[0]
pbar.update()
# ---- Unpack and denormalize ----
latents = self._unpack_latents(
latents,
latent_num_frames,
latent_height,
latent_width,
self.transformer_spatial_patch_size,
self.transformer_temporal_patch_size,
)
latents = self._denormalize_latents(
latents,
self.vae.latents_mean,
self.vae.latents_std,
self.vae.config.scaling_factor,
)
audio_latents = self._unpad_audio_latents(audio_latents, original_audio_num_frames)
audio_latents = self._denormalize_audio_latents(
audio_latents,
self.audio_vae.latents_mean,
self.audio_vae.latents_std,
)
audio_latents = self._unpack_audio_latents(
audio_latents,
original_audio_num_frames,
num_mel_bins=latent_mel_bins,
)
# ---- Decode ----
if output_type == "latent":
video = latents
audio = audio_latents
else:
latents = latents.to(connector_prompt_embeds.dtype)
if not self.vae.config.timestep_conditioning:
timestep_decode = None
else:
noise = randn_tensor(latents.shape, generator=generator, device=device, dtype=latents.dtype)
if not isinstance(decode_timestep, list):
decode_timestep = [decode_timestep] * batch_size
if decode_noise_scale is None:
decode_noise_scale = decode_timestep
elif not isinstance(decode_noise_scale, list):
decode_noise_scale = [decode_noise_scale] * batch_size
timestep_decode = torch.tensor(decode_timestep, device=device, dtype=latents.dtype)
decode_noise_scale_t = torch.tensor(decode_noise_scale, device=device, dtype=latents.dtype)[
:, None, None, None, None
]
latents = (1 - decode_noise_scale_t) * latents + decode_noise_scale_t * noise
# Move VAE, audio_vae, vocoder to GPU for decoding
self.vae.to(device)
latents = latents.to(self.vae.dtype)
video = self.vae.decode(latents, timestep_decode, return_dict=False)[0]
video = self.video_processor.postprocess_video(video, output_type=output_type)
self.vae.to("cpu")
self.audio_vae.to(device)
audio_latents = audio_latents.to(self.audio_vae.dtype)
generated_mel_spectrograms = self.audio_vae.decode(audio_latents, return_dict=False)[0]
self.audio_vae.to("cpu")
self.vocoder.to(device)
audio = self.vocoder(generated_mel_spectrograms)
self.vocoder.to("cpu")
torch.cuda.empty_cache()
return DiffusionOutput(output=(video, audio))
def load_weights(self, weights: Iterable[tuple[str, torch.Tensor]]) -> set[str]:
loader = AutoWeightsLoader(self)
return loader.load_weights(weights)
class LTX23ImageToVideoPipeline(nn.Module):
"""LTX-2.3 image-to-video pipeline placeholder."""
def __init__(self, *, od_config: OmniDiffusionConfig, prefix: str = ""):
super().__init__()
raise NotImplementedError(
"LTX23ImageToVideoPipeline is not yet implemented. "
"Use LTX23Pipeline for single-stage text-to-video generation."
)