Files
vllm-omni/vllm_omni/diffusion/models/ltx2/ltx2_denoise.py
T
2026-08-15 18:27:23 +08:00

632 lines
24 KiB
Python

# 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
import math
from collections.abc import Callable, Iterable
from dataclasses import dataclass
from typing import TYPE_CHECKING, Any, Protocol
import torch
from diffusers.pipelines.stable_diffusion.pipeline_stable_diffusion import retrieve_timesteps
from vllm_omni.diffusion.worker.request_batch import DiffusionRequestBatch
from .ltx2_guidance import euler_step_from_velocity
from .ltx2_latents import LTXAVState, unpack_audio_latents, unpad_audio_latents
if TYPE_CHECKING:
from .ltx2_conditioning import LTXPromptContext
from .ltx2_recipes import LTXPhaseRecipe
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
guidance_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
sampler: str
audio_scheduler: Any
video_audio_step_adapter: 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
audio_attention_mask: torch.Tensor | None = None
conditioning_mask: torch.Tensor | None = None
conditioning_mask_for_model: torch.Tensor | None = None
@dataclass
class LTXPhaseResult:
"""Denoised AV latents and the context used to produce them."""
forward_context: LTXForwardContext
video: torch.Tensor
audio: torch.Tensor
audio_for_next_phase: torch.Tensor | None = None
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]
LTX_ANCESTRAL_ETA = 1.0
LTX_ANCESTRAL_S_NOISE = 1.0
LTX_ANCESTRAL_NOISE_SEED_OFFSET = 10000
LTX_OFFICIAL_DEFAULT_SEED = 10
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 LTXVideoAudioStepAdapter:
"""Expose the shared LTX Euler update through the distributed scheduler API."""
def __init__(
self,
pipeline: Any,
audio_scheduler: Any,
latent_num_frames: int,
latent_height: int,
latent_width: int,
*,
image_conditioned: bool,
sampler: str = "euler",
generator: torch.Generator | list[torch.Generator] | None = None,
conditioning_mask: torch.Tensor | None = None,
) -> None:
self._pipeline = pipeline
self._audio_scheduler = audio_scheduler
self._latent_num_frames = latent_num_frames
self._latent_height = latent_height
self._latent_width = latent_width
self._image_conditioned = image_conditioned
self._sampler = sampler
self._conditioning_mask = conditioning_mask
self._ancestral_generators = (
_make_ancestral_generators(generator, pipeline.device) if sampler == "euler_ancestral" else None
)
self._step_index = 0
def step(self, noise_pred, t, latents, return_dict=False, generator=None):
del t, return_dict, generator
if self._sampler == "euler_ancestral":
video_out = _ancestral_euler_step_from_velocity(
latents[0],
noise_pred[0],
self._pipeline.scheduler.sigmas,
self._step_index,
self._ancestral_generators,
)
if self._conditioning_mask is not None:
mask = self._conditioning_mask.unsqueeze(-1).to(video_out.dtype)
video_out = torch.lerp(video_out, latents[0], mask)
elif self._image_conditioned:
video_out = self._pipeline._step_video_latents_i2v(
noise_pred[0],
latents[0],
self._step_index,
self._latent_num_frames,
self._latent_height,
self._latent_width,
)
else:
video_out = euler_step_from_velocity(
latents[0],
noise_pred[0],
self._pipeline.scheduler.sigmas,
self._step_index,
)
if self._sampler == "euler_ancestral":
audio_out = _ancestral_euler_step_from_velocity(
latents[1],
noise_pred[1],
self._audio_scheduler.sigmas,
self._step_index,
self._ancestral_generators,
)
else:
audio_out = euler_step_from_velocity(
latents[1],
noise_pred[1],
self._audio_scheduler.sigmas,
self._step_index,
)
self._step_index += 1
return ((video_out, audio_out),)
def _make_ancestral_generators(
generator: torch.Generator | list[torch.Generator] | None,
device: torch.device,
) -> torch.Generator | list[torch.Generator]:
"""Create the official independent ``seed + 10000`` noise stream."""
def _offset(source: torch.Generator | None) -> torch.Generator:
seed = LTX_OFFICIAL_DEFAULT_SEED if source is None else source.initial_seed()
return torch.Generator(device=device).manual_seed(seed + LTX_ANCESTRAL_NOISE_SEED_OFFSET)
if isinstance(generator, list):
return [_offset(item) for item in generator]
return _offset(generator)
def _randn_like_with_generators(
sample: torch.Tensor,
generators: torch.Generator | list[torch.Generator],
) -> torch.Tensor:
if not isinstance(generators, list):
return torch.randn(sample.shape, generator=generators, dtype=sample.dtype, device=sample.device)
if len(generators) != sample.shape[0]:
raise ValueError(
f"LTX ancestral sampling received {len(generators)} generators for batch size {sample.shape[0]}."
)
return torch.cat(
[
torch.randn((1, *sample.shape[1:]), generator=item, dtype=sample.dtype, device=sample.device)
for item in generators
]
)
def _ancestral_euler_step_from_velocity(
sample: torch.Tensor,
velocity: torch.Tensor,
sigmas: torch.Tensor,
step_index: int,
generators: torch.Generator | list[torch.Generator] | None,
) -> torch.Tensor:
"""Apply the official LTX-2.5 rectified-flow ancestral Euler step."""
sigma = sigmas[step_index].to(torch.float32)
sigma_next = sigmas[step_index + 1].to(torch.float32)
# Official X0Model materializes the denoised prediction in the model
# dtype before the ancestral step promotes it back to float32.
denoised_model_dtype = (sample.float() - velocity.float() * sigma).to(sample.dtype)
denoised = denoised_model_dtype.float()
if sigma_next == 0:
return denoised.to(sample.dtype)
if generators is None:
raise ValueError("LTX ancestral Euler sampling requires a noise generator.")
downstep_ratio = 1.0 + (sigma_next / sigma - 1.0) * LTX_ANCESTRAL_ETA
sigma_down = sigma_next * downstep_ratio
sigma_down_ratio = sigma_down / sigma
x_next = sigma_down_ratio * sample.float() + (1.0 - sigma_down_ratio) * denoised
alpha_next = 1.0 - sigma_next
alpha_down = 1.0 - sigma_down
renoise_coeff = (sigma_next**2 - sigma_down**2 * alpha_next**2 / alpha_down**2).clamp(min=0).sqrt()
noise = _randn_like_with_generators(sample, generators)
x_next = (alpha_next / alpha_down) * x_next + noise.float() * LTX_ANCESTRAL_S_NOISE * renoise_coeff
result = x_next.to(sample.dtype)
return result
def _official_ltx_sigmas(
scheduler: Any,
steps: int,
device: torch.device,
) -> torch.Tensor:
"""Build the official LTX one-stage sigma schedule in torch fp32."""
config = scheduler.config
base_anchor = config.get("base_image_seq_len", 1024)
max_anchor = config.get("max_image_seq_len", 4096)
base_shift = config.get("base_shift", 0.95)
max_shift = config.get("max_shift", 2.05)
sigmas = torch.linspace(1.0, 0.0, steps + 1)
slope = (max_shift - base_shift) / (max_anchor - base_anchor)
# Official LTX one-stage pipelines omit the latent when constructing
# this schedule, so the shift stays at the max sequence anchor.
sigma_shift = max_anchor * slope + (base_shift - slope * base_anchor)
exp_shift = math.exp(sigma_shift)
sigmas = torch.where(sigmas != 0, exp_shift / (exp_shift + (1 / sigmas - 1)), 0)
# Official non-distilled checkpoints explicitly set this to 0.1. Missing
# or None means the loaded scheduler disabled terminal stretching.
terminal = config.get("shift_terminal")
if terminal is not None:
non_zero = sigmas != 0
one_minus_sigmas = 1.0 - sigmas[non_zero]
scale = one_minus_sigmas[-1] / (1.0 - terminal)
sigmas[non_zero] = 1.0 - one_minus_sigmas / scale
return sigmas.to(dtype=torch.float32, device=device)
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,
use_official_sigma_schedule: bool,
image_conditioned: bool = False,
sampler: str = "euler",
generator: torch.Generator | list[torch.Generator] | None = None,
conditioning_mask: torch.Tensor | None = None,
) -> 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_step_adapter = LTXVideoAudioStepAdapter(
pipeline,
audio_scheduler,
latent_num_frames,
latent_height,
latent_width,
image_conditioned=image_conditioned,
sampler=sampler,
generator=generator,
conditioning_mask=conditioning_mask,
)
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_step_adapter, timesteps_tensor
if sigmas is None and timesteps is None and use_official_sigma_schedule:
scheduler_sigmas = _official_ltx_sigmas(pipeline.scheduler, request_inputs.num_inference_steps, device)
timesteps_tensor = _set_scheduler_sigmas(pipeline.scheduler, scheduler_sigmas)
_set_scheduler_sigmas(audio_scheduler, scheduler_sigmas.clone())
return audio_scheduler, video_audio_step_adapter, timesteps_tensor
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_step_adapter, timesteps_tensor
def prepare_rope_coords_stage(
pipeline: Any,
forward_ctx: LTXForwardContext,
latents: torch.Tensor,
audio_latents: torch.Tensor,
) -> tuple[torch.Tensor, torch.Tensor]:
transformer = pipeline.transformer
video_coords = 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 = 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 _first_frame_keyframes_mask(reference: torch.Tensor, latent_num_frames: int) -> torch.Tensor:
"""Mark the first causal latent frame, matching official LTX-2.5."""
if latent_num_frames <= 0:
raise ValueError(f"LTX latent frame count must be positive, got {latent_num_frames}.")
tokens_per_frame, remainder = divmod(reference.shape[1], latent_num_frames)
if remainder:
raise ValueError(
f"LTX video token count {reference.shape[1]} is not divisible by {latent_num_frames} latent frames."
)
mask = reference.new_zeros((reference.shape[0], reference.shape[1], 1))
mask[:, :tokens_per_frame] = 1
return mask
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,
attention_kwargs: dict[str, Any] | None = None,
) -> dict[str, Any]:
del encoder_attention_mask, audio_encoder_attention_mask
keyframes_mask = None
if getattr(pipeline.transformer.config, "use_keyframes_abs_pos_embedding", False):
keyframes_mask = _first_frame_keyframes_mask(hidden_states, forward_ctx.latent_num_frames)
return {
"hidden_states": hidden_states,
"audio_hidden_states": audio_hidden_states,
"keyframes_mask": keyframes_mask,
"encoder_hidden_states": encoder_hidden_states,
"audio_encoder_hidden_states": audio_encoder_hidden_states,
**pipeline._denoise_timestep_kwargs(
ts,
forward_ctx,
denoise_ctx,
video_token_count=hidden_states.shape[1],
audio_token_count=audio_hidden_states.shape[1],
),
# This is valid only because LTX connectors replace every padding token
# with a learned register, making all output context tokens valid.
"encoder_attention_mask": None,
"audio_encoder_attention_mask": None,
"audio_attention_mask": denoise_ctx.audio_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 if attention_kwargs is None else 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_step_adapter,
)
return pipeline._synchronize_guidance_parallel_step_output(
latents,
guidance_parallel_ready=forward_ctx.guidance_parallel_ready,
)
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,
phase_recipe: LTXPhaseRecipe,
image: Any | None = None,
prompt_context: LTXPromptContext | None = None,
) -> LTXPhaseResult:
pipeline._check_forward_inputs(request_inputs, image=image)
guidance_parallel_ready = pipeline._setup_forward_runtime(req, 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_step_adapter, 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,
use_official_sigma_schedule=phase_recipe.use_official_sigma_schedule,
image_conditioned=conditioning_mask is not None,
sampler=phase_recipe.sampler,
generator=request_inputs.generator,
conditioning_mask=conditioning_mask,
)
forward_ctx = LTXForwardContext(
req=req,
request_inputs=request_inputs,
prompt_context=prompt_context,
device=device,
guidance_parallel_ready=guidance_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,
sampler=phase_recipe.sampler,
audio_scheduler=audio_scheduler,
video_audio_step_adapter=video_audio_step_adapter,
)
video_coords, audio_coords = prepare_rope_coords_stage(pipeline, forward_ctx, latents, audio_latents)
ring_degree = getattr(pipeline.od_config.parallel_config, "ring_degree", 1) or 1
if padded_audio_num_frames > original_audio_num_frames and ring_degree > 1:
raise ValueError(
"LTX audio padding requires an attention mask, which Ring sequence parallelism does not support. "
"Use Ulysses-only SP or choose a request whose audio latent length is divisible by the SP size."
)
denoise_ctx = LTXDenoiseContext(
latents=latents,
audio_latents=audio_latents,
video_coords=video_coords,
audio_coords=audio_coords,
audio_attention_mask=(
torch.arange(padded_audio_num_frames, device=audio_latents.device)
.lt(original_audio_num_frames)
.unsqueeze(0)
.expand(audio_latents.shape[0], -1)
if padded_audio_num_frames > original_audio_num_frames
else None
),
conditioning_mask=conditioning_mask,
)
denoise_ctx = pipeline._prepare_denoise_context_for_guidance(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,
)
normalized_audio = unpack_audio_latents(
unpad_audio_latents(state.audio, forward_ctx.original_audio_num_frames),
num_mel_bins=forward_ctx.latent_mel_bins,
)
return LTXPhaseResult(
forward_context=forward_ctx,
video=latents,
audio=audio_latents,
audio_for_next_phase=normalized_audio,
)