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vllm-omni/vllm_omni/diffusion/models/ltx2/ltx2_denoise.py
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# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""Shared denoise execution primitives for LTX pipelines."""
from __future__ import annotations
import copy
from collections.abc import Callable, Iterable
from dataclasses import dataclass
from typing import TYPE_CHECKING, Any, Protocol
import numpy as np
import torch
from diffusers.pipelines.stable_diffusion.pipeline_stable_diffusion import retrieve_timesteps
from vllm_omni.diffusion.worker.request_batch import DiffusionRequestBatch
from .ltx2_latents import LTXAVState
if TYPE_CHECKING:
from .ltx2_conditioning import LTXPromptContext
from .ltx2_request import LTXRequestInputs
@dataclass
class LTXForwardContext:
"""Immutable metadata and schedulers for one LTX denoise phase."""
req: DiffusionRequestBatch
request_inputs: LTXRequestInputs
prompt_context: LTXPromptContext
device: torch.device
cfg_parallel_ready: bool
attention_kwargs: dict[str, Any] | None
latent_num_frames: int
latent_height: int
latent_width: int
latent_mel_bins: int
original_audio_num_frames: int
padded_audio_num_frames: int
timesteps: torch.Tensor
audio_scheduler: Any
video_audio_scheduler: Any
@property
def batch_size(self) -> int:
return self.prompt_context.batch_size
@property
def num_videos_per_prompt(self) -> int:
return self.request_inputs.num_videos_per_prompt
@dataclass
class LTXDenoiseContext:
"""Mutable AV state and positional metadata for a denoise phase."""
latents: torch.Tensor
audio_latents: torch.Tensor
video_coords: torch.Tensor
audio_coords: torch.Tensor
conditioning_mask: torch.Tensor | None = None
conditioning_mask_for_model: torch.Tensor | None = None
@dataclass
class LTXPhaseResult:
"""Denoised, unpacked AV latents and the context used to produce them."""
forward_context: LTXForwardContext
video: torch.Tensor
audio: torch.Tensor
class LTXDenoisePipeline(Protocol):
"""Pipeline state required by :class:`LTXDenoiseExecutor`."""
@property
def interrupt(self) -> bool: ...
def progress_bar(self, iterable=None, total=None): ...
LTXDenoiseStep = Callable[[int, torch.Tensor, LTXAVState], LTXAVState]
class LTXDenoiseExecutor:
"""Run the one shared LTX denoise loop.
Prediction and scheduler math remain injectable so structural refactors do
not change the existing LTX2/LTX2.3 numerical paths. Guidance will replace
that step policy independently.
"""
@staticmethod
def run(
pipeline: LTXDenoisePipeline,
state: LTXAVState,
timesteps: Iterable[torch.Tensor],
step: LTXDenoiseStep,
) -> LTXAVState:
timesteps = tuple(timesteps)
with pipeline.progress_bar(total=len(timesteps)) as progress_bar:
for index, timestep in enumerate(timesteps):
if pipeline.interrupt:
continue
state = step(index, timestep, state)
progress_bar.update()
return state
def calculate_shift(
image_seq_len: int,
base_seq_len: int = 256,
max_seq_len: int = 4096,
base_shift: float = 0.5,
max_shift: float = 1.15,
) -> float:
slope = (max_shift - base_shift) / (max_seq_len - base_seq_len)
intercept = base_shift - slope * base_seq_len
return image_seq_len * slope + intercept
class VideoAudioScheduler:
"""Composite scheduler dispatching video and audio updates."""
def __init__(self, video_scheduler, audio_scheduler):
self.video_scheduler = video_scheduler
self.audio_scheduler = audio_scheduler
def step(self, noise_pred, t, latents, return_dict=False, generator=None):
video_out = self.video_scheduler.step(
noise_pred[0],
t[0],
latents[0],
return_dict=False,
generator=generator,
)[0]
audio_out = self.audio_scheduler.step(
noise_pred[1],
t[1],
latents[1],
return_dict=False,
generator=generator,
)[0]
return ((video_out, audio_out),)
class I2VVideoAudioScheduler:
"""Update the unconditioned video frames and the full audio state."""
def __init__(self, pipeline, audio_scheduler, latent_num_frames, latent_height, latent_width):
self.video_scheduler = pipeline.scheduler
self.audio_scheduler = audio_scheduler
self._pipeline = pipeline
self._latent_num_frames = latent_num_frames
self._latent_height = latent_height
self._latent_width = latent_width
def step(self, noise_pred, t, latents, return_dict=False, generator=None):
video_out = self._pipeline._step_video_latents_i2v(
noise_pred[0],
latents[0],
t[0],
self._latent_num_frames,
self._latent_height,
self._latent_width,
)
audio_out = self.audio_scheduler.step(
noise_pred[1],
t[1],
latents[1],
return_dict=False,
generator=generator,
)[0]
return ((video_out, audio_out),)
def _set_scheduler_sigmas(scheduler: Any, sigmas: torch.Tensor) -> torch.Tensor:
sigmas = sigmas.to(torch.float32)
timesteps = sigmas[:-1] * scheduler.config.get("num_train_timesteps", 1000)
scheduler.sigmas = sigmas
scheduler.timesteps = timesteps
scheduler.num_inference_steps = len(timesteps)
scheduler._step_index = None
scheduler._begin_index = None
return timesteps
def prepare_scheduler_stage(
pipeline: Any,
request_inputs: LTXRequestInputs,
*,
device: torch.device,
sigmas: list[float] | None,
timesteps: list[int] | None,
latent_num_frames: int,
latent_height: int,
latent_width: int,
) -> tuple[Any, Any, torch.Tensor]:
if sigmas is not None and timesteps is not None:
raise ValueError("Only one of `sigmas` or `timesteps` may be provided.")
audio_scheduler = copy.deepcopy(pipeline.scheduler)
video_audio_scheduler = pipeline._make_video_audio_scheduler(
audio_scheduler,
latent_num_frames,
latent_height,
latent_width,
)
if sigmas is not None:
scheduler_sigmas = torch.as_tensor(sigmas, dtype=torch.float32, device=device)
if scheduler_sigmas.ndim != 1 or scheduler_sigmas.numel() < 2:
raise ValueError("An LTX custom sigma schedule must contain at least two boundary values.")
if scheduler_sigmas[-1] != 0:
scheduler_sigmas = torch.cat([scheduler_sigmas, scheduler_sigmas.new_zeros(1)])
timesteps_tensor = _set_scheduler_sigmas(pipeline.scheduler, scheduler_sigmas)
_set_scheduler_sigmas(audio_scheduler, scheduler_sigmas.clone())
return audio_scheduler, video_audio_scheduler, timesteps_tensor
sigmas = np.linspace(1.0, 1 / request_inputs.num_inference_steps, request_inputs.num_inference_steps)
# Official LTX2 one-stage omits the latent, so mu stays at max_shift across resolutions.
# Mu varies with latent token count only when the scheduler receives a latent, as in official HQ two-stage;
# explicit sigma schedules bypass mu entirely.
mu = calculate_shift(
pipeline.scheduler.config.get("max_image_seq_len", 4096),
pipeline.scheduler.config.get("base_image_seq_len", 1024),
pipeline.scheduler.config.get("max_image_seq_len", 4096),
pipeline.scheduler.config.get("base_shift", 0.95),
pipeline.scheduler.config.get("max_shift", 2.05),
)
retrieve_timesteps(
audio_scheduler,
request_inputs.num_inference_steps,
device,
timesteps,
sigmas=sigmas,
mu=mu,
)
timesteps_tensor, _ = retrieve_timesteps(
pipeline.scheduler,
request_inputs.num_inference_steps,
device,
timesteps,
sigmas=sigmas,
mu=mu,
)
return audio_scheduler, video_audio_scheduler, timesteps_tensor
def prepare_rope_coords_stage(
pipeline: Any,
forward_ctx: LTXForwardContext,
latents: torch.Tensor,
audio_latents: torch.Tensor,
) -> tuple[torch.Tensor, torch.Tensor]:
video_coords = pipeline.transformer.rope.prepare_video_coords(
latents.shape[0],
forward_ctx.latent_num_frames,
forward_ctx.latent_height,
forward_ctx.latent_width,
latents.device,
fps=forward_ctx.request_inputs.frame_rate,
)
audio_coords = pipeline.transformer.audio_rope.prepare_audio_coords(
audio_latents.shape[0],
forward_ctx.padded_audio_num_frames,
audio_latents.device,
)
return video_coords, audio_coords
def build_transformer_kwargs(
pipeline: Any,
forward_ctx: LTXForwardContext,
denoise_ctx: LTXDenoiseContext,
*,
hidden_states: torch.Tensor,
audio_hidden_states: torch.Tensor,
encoder_hidden_states: torch.Tensor,
audio_encoder_hidden_states: torch.Tensor,
encoder_attention_mask: torch.Tensor | None,
audio_encoder_attention_mask: torch.Tensor | None,
ts: torch.Tensor,
) -> dict[str, Any]:
return {
"hidden_states": hidden_states,
"audio_hidden_states": audio_hidden_states,
"encoder_hidden_states": encoder_hidden_states,
"audio_encoder_hidden_states": audio_encoder_hidden_states,
**pipeline._denoise_timestep_kwargs(ts, forward_ctx, denoise_ctx),
"encoder_attention_mask": encoder_attention_mask,
"audio_encoder_attention_mask": audio_encoder_attention_mask,
"num_frames": forward_ctx.latent_num_frames,
"height": forward_ctx.latent_height,
"width": forward_ctx.latent_width,
"fps": forward_ctx.request_inputs.frame_rate,
"audio_num_frames": forward_ctx.padded_audio_num_frames,
"video_coords": denoise_ctx.video_coords,
"audio_coords": denoise_ctx.audio_coords,
"attention_kwargs": forward_ctx.attention_kwargs,
"return_dict": False,
}
def step_denoised_latents(
pipeline: Any,
forward_ctx: LTXForwardContext,
denoise_ctx: LTXDenoiseContext,
noise_pred_video: torch.Tensor,
noise_pred_audio: torch.Tensor,
timestep: torch.Tensor,
) -> tuple[torch.Tensor, torch.Tensor]:
latents = pipeline.scheduler_step_maybe_with_cfg(
(noise_pred_video, noise_pred_audio),
(timestep, timestep),
(denoise_ctx.latents, denoise_ctx.audio_latents),
do_true_cfg=pipeline.do_classifier_free_guidance,
per_request_scheduler=forward_ctx.video_audio_scheduler,
)
return pipeline._synchronize_cfg_parallel_step_output(
latents,
do_true_cfg=pipeline.do_classifier_free_guidance,
)
class LTXPhaseExecutor:
"""Prepare and execute one LTX phase without owning model modules."""
@staticmethod
def run(
pipeline: Any,
req: DiffusionRequestBatch,
request_inputs: LTXRequestInputs,
*,
noise_scale: float,
sigmas: list[float] | None,
timesteps: list[int] | None,
attention_kwargs: dict[str, Any] | None,
image: Any | None = None,
prompt_context: LTXPromptContext | None = None,
) -> LTXPhaseResult:
pipeline._check_forward_inputs(request_inputs, image=image)
cfg_parallel_ready = pipeline._setup_forward_runtime(request_inputs, attention_kwargs)
device = pipeline.device
if prompt_context is None:
prompt_context = pipeline._prepare_prompt_context(
prompt=request_inputs.prompt,
negative_prompt=request_inputs.negative_prompt,
prompt_embeds=request_inputs.prompt_embeds,
negative_prompt_embeds=request_inputs.negative_prompt_embeds,
prompt_attention_mask=request_inputs.prompt_attention_mask,
negative_prompt_attention_mask=request_inputs.negative_prompt_attention_mask,
num_videos_per_prompt=request_inputs.num_videos_per_prompt,
max_sequence_length=request_inputs.max_sequence_length,
)
latent_num_frames, latent_height, latent_width = pipeline._resolve_video_latent_dimensions(request_inputs)
latents, conditioning_mask = pipeline._prepare_video_latents_stage(
request_inputs,
prompt_context,
device=device,
noise_scale=noise_scale,
image=image,
)
audio_latents, original_audio_num_frames, padded_audio_num_frames, latent_mel_bins = (
pipeline._prepare_audio_latents_stage(
request_inputs,
prompt_context,
device=device,
noise_scale=noise_scale,
)
)
audio_scheduler, video_audio_scheduler, timesteps_tensor = prepare_scheduler_stage(
pipeline,
request_inputs,
device=device,
sigmas=sigmas,
timesteps=timesteps,
latent_num_frames=latent_num_frames,
latent_height=latent_height,
latent_width=latent_width,
)
forward_ctx = LTXForwardContext(
req=req,
request_inputs=request_inputs,
prompt_context=prompt_context,
device=device,
cfg_parallel_ready=cfg_parallel_ready,
attention_kwargs=attention_kwargs,
latent_num_frames=latent_num_frames,
latent_height=latent_height,
latent_width=latent_width,
latent_mel_bins=latent_mel_bins,
original_audio_num_frames=original_audio_num_frames,
padded_audio_num_frames=padded_audio_num_frames,
timesteps=timesteps_tensor,
audio_scheduler=audio_scheduler,
video_audio_scheduler=video_audio_scheduler,
)
video_coords, audio_coords = prepare_rope_coords_stage(pipeline, forward_ctx, latents, audio_latents)
denoise_ctx = LTXDenoiseContext(
latents=latents,
audio_latents=audio_latents,
video_coords=video_coords,
audio_coords=audio_coords,
conditioning_mask=conditioning_mask,
)
denoise_ctx = pipeline._prepare_denoise_context_for_cfg(forward_ctx, denoise_ctx)
state = LTXDenoiseExecutor.run(
pipeline,
LTXAVState(video=denoise_ctx.latents, audio=denoise_ctx.audio_latents),
forward_ctx.timesteps,
lambda index, timestep, state: pipeline._denoise_step(
index,
timestep,
state,
forward_ctx,
denoise_ctx,
),
)
denoise_ctx.latents = state.video
denoise_ctx.audio_latents = state.audio
latents, audio_latents = pipeline._unpack_and_denormalize_stage(
forward_ctx,
state.video,
state.audio,
)
return LTXPhaseResult(forward_context=forward_ctx, video=latents, audio=audio_latents)