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vllm-omni/vllm_omni/diffusion/postprocess/rife_interpolator.py
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# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""
RIFE 4.22.lite frame interpolation for vLLM-Omni video generation.
RIFE model code is vendored and adapted from:
- https://github.com/hzwer/ECCV2022-RIFE (MIT License)
- https://github.com/hzwer/Practical-RIFE (MIT License)
Copyright (c) 2021 Zhewei Huang
The FrameInterpolator wrapper and vLLM-Omni integration code are original work.
"""
from __future__ import annotations
import os
import threading
from typing import Any
import torch
import torch.nn as nn
import torch.nn.functional as F
from vllm.logger import init_logger
logger = init_logger(__name__)
_DEFAULT_RIFE_HF_REPO = "elfgum/RIFE-4.22.lite"
_MODEL_CACHE: dict[tuple[str, str], Model] = {}
_MODEL_CACHE_LOCK = threading.Lock()
def warp(ten_input: torch.Tensor, ten_flow: torch.Tensor) -> torch.Tensor:
"""Warp input tensor by optical flow using grid_sample."""
ten_horizontal = (
torch.linspace(-1.0, 1.0, ten_flow.shape[3], device=ten_flow.device)
.view(1, 1, 1, ten_flow.shape[3])
.expand(ten_flow.shape[0], -1, ten_flow.shape[2], -1)
)
ten_vertical = (
torch.linspace(-1.0, 1.0, ten_flow.shape[2], device=ten_flow.device)
.view(1, 1, ten_flow.shape[2], 1)
.expand(ten_flow.shape[0], -1, -1, ten_flow.shape[3])
)
ten_grid = torch.cat([ten_horizontal, ten_vertical], dim=1)
ten_flow = torch.cat(
[
ten_flow[:, 0:1, :, :] / ((ten_input.shape[3] - 1.0) / 2.0),
ten_flow[:, 1:2, :, :] / ((ten_input.shape[2] - 1.0) / 2.0),
],
dim=1,
)
grid = (ten_grid + ten_flow).permute(0, 2, 3, 1)
return F.grid_sample(
input=ten_input,
grid=grid,
mode="bilinear",
padding_mode="border",
align_corners=True,
)
def _conv(
in_planes: int,
out_planes: int,
kernel_size: int = 3,
stride: int = 1,
padding: int = 1,
dilation: int = 1,
) -> nn.Sequential:
return nn.Sequential(
nn.Conv2d(
in_planes,
out_planes,
kernel_size=kernel_size,
stride=stride,
padding=padding,
dilation=dilation,
bias=True,
),
nn.LeakyReLU(0.2, True),
)
class ResConv(nn.Module):
"""Residual convolution block with learnable beta scaling."""
def __init__(self, c: int, dilation: int = 1):
super().__init__()
self.conv = nn.Conv2d(c, c, 3, 1, dilation, dilation=dilation, groups=1)
self.beta = nn.Parameter(torch.ones((1, c, 1, 1)), requires_grad=True)
self.relu = nn.LeakyReLU(0.2, True)
def forward(self, x: torch.Tensor) -> torch.Tensor:
return self.relu(self.conv(x) * self.beta + x)
class IFBlock(nn.Module):
"""Single-scale optical flow, mask, and feature block."""
def __init__(self, in_planes: int, c: int = 64):
super().__init__()
self.conv0 = nn.Sequential(
_conv(in_planes, c // 2, 3, 2, 1),
_conv(c // 2, c, 3, 2, 1),
)
self.convblock = nn.Sequential(
ResConv(c),
ResConv(c),
ResConv(c),
ResConv(c),
ResConv(c),
ResConv(c),
ResConv(c),
ResConv(c),
)
self.lastconv = nn.Sequential(
nn.ConvTranspose2d(c, 4 * 13, 4, 2, 1),
nn.PixelShuffle(2),
)
def forward(
self,
x: torch.Tensor,
flow: torch.Tensor | None = None,
scale: float = 1.0,
) -> tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
x = F.interpolate(x, scale_factor=1.0 / scale, mode="bilinear", align_corners=False)
if flow is not None:
flow = (
F.interpolate(
flow,
scale_factor=1.0 / scale,
mode="bilinear",
align_corners=False,
)
* 1.0
/ scale
)
x = torch.cat((x, flow), 1)
feat = self.conv0(x)
feat = self.convblock(feat)
tmp = self.lastconv(feat)
tmp = F.interpolate(tmp, scale_factor=scale, mode="bilinear", align_corners=False)
flow = tmp[:, :4] * scale
mask = tmp[:, 4:5]
feat = tmp[:, 5:]
return flow, mask, feat
class Head(nn.Module):
"""Feature encoder producing four-channel features at full resolution."""
def __init__(self):
super().__init__()
self.cnn0 = nn.Conv2d(3, 16, 3, 2, 1)
self.cnn1 = nn.Conv2d(16, 16, 3, 1, 1)
self.cnn2 = nn.Conv2d(16, 16, 3, 1, 1)
self.cnn3 = nn.ConvTranspose2d(16, 4, 4, 2, 1)
self.relu = nn.LeakyReLU(0.2, True)
def forward(self, x: torch.Tensor) -> torch.Tensor:
x0 = self.cnn0(x)
x = self.relu(x0)
x1 = self.cnn1(x)
x = self.relu(x1)
x2 = self.cnn2(x)
x = self.relu(x2)
x3 = self.cnn3(x)
return x3
class IFNet(nn.Module):
"""Four-scale IFNet optical flow network."""
def __init__(self):
super().__init__()
self.block0 = IFBlock(7 + 8, c=192)
self.block1 = IFBlock(8 + 4 + 8 + 8, c=128)
self.block2 = IFBlock(8 + 4 + 8 + 8, c=64)
self.block3 = IFBlock(8 + 4 + 8 + 8, c=32)
self.encode = Head()
def forward(
self,
x: torch.Tensor,
timestep: float = 0.5,
scale_list: list[float] | None = None,
) -> tuple[list[torch.Tensor], torch.Tensor, list[tuple[torch.Tensor, torch.Tensor] | torch.Tensor]]:
if scale_list is None:
scale_list = [8, 4, 2, 1]
channel = x.shape[1] // 2
img0 = x[:, :channel]
img1 = x[:, channel:]
if not torch.is_tensor(timestep):
timestep = (x[:, :1].clone() * 0 + 1) * timestep
else:
timestep = timestep.repeat(1, 1, img0.shape[2], img0.shape[3])
f0 = self.encode(img0[:, :3])
f1 = self.encode(img1[:, :3])
flow_list: list[torch.Tensor] = []
merged: list[tuple[torch.Tensor, torch.Tensor] | torch.Tensor] = []
mask_list: list[torch.Tensor] = []
warped_img0 = img0
warped_img1 = img1
flow = None
mask = None
for i, block in enumerate([self.block0, self.block1, self.block2, self.block3]):
if flow is None:
flow, mask, feat = block(
torch.cat((img0[:, :3], img1[:, :3], f0, f1, timestep), 1),
None,
scale=scale_list[i],
)
else:
wf0 = warp(f0, flow[:, :2])
wf1 = warp(f1, flow[:, 2:4])
fd, m0, feat = block(
torch.cat(
(
warped_img0[:, :3],
warped_img1[:, :3],
wf0,
wf1,
timestep,
mask,
feat,
),
1,
),
flow,
scale=scale_list[i],
)
mask = m0
flow = flow + fd
mask_list.append(mask)
flow_list.append(flow)
warped_img0 = warp(img0, flow[:, :2])
warped_img1 = warp(img1, flow[:, 2:4])
merged.append((warped_img0, warped_img1))
mask = torch.sigmoid(mask)
merged[3] = warped_img0 * mask + warped_img1 * (1 - mask)
return flow_list, mask_list[3], merged
class Model:
"""Wraps IFNet and exposes RIFE-compatible load/inference helpers."""
def __init__(self):
self.flownet = IFNet()
def eval(self) -> Model:
self.flownet.eval()
return self
def device(self) -> torch.device:
return next(self.flownet.parameters()).device
def load_model(self, path: str) -> None:
flownet_path = os.path.join(path, "flownet.pkl")
if not os.path.isfile(flownet_path):
raise FileNotFoundError(
f"RIFE weight file not found: {flownet_path}. Expected layout: <model_path>/flownet.pkl"
)
state = torch.load(flownet_path, map_location="cpu", weights_only=False)
state = {k.removeprefix("module."): v for k, v in state.items()}
self.flownet.load_state_dict(state, strict=False)
logger.info("Loaded RIFE weights from %s", flownet_path)
def inference(
self,
img0: torch.Tensor,
img1: torch.Tensor,
scale: float = 1.0,
timestep: float = 0.5,
) -> torch.Tensor:
_n, _c, h, w = img0.shape
ph = ((h - 1) // 32 + 1) * 32
pw = ((w - 1) // 32 + 1) * 32
pad = (0, pw - w, 0, ph - h)
img0 = F.pad(img0, pad)
img1 = F.pad(img1, pad)
imgs = torch.cat((img0, img1), 1)
scale_list = [8 / scale, 4 / scale, 2 / scale, 1 / scale]
with torch.no_grad():
_flow_list, _mask, merged = self.flownet(
imgs,
timestep=timestep,
scale_list=scale_list,
)
return merged[3][:, :, :h, :w]
def _resolve_rife_model_path(model_path: str | None) -> str:
model_path = model_path or _DEFAULT_RIFE_HF_REPO
if os.path.isdir(model_path):
return model_path
from vllm_omni.model_executor.model_loader.weight_utils import (
download_weights_from_hf_specific,
)
return download_weights_from_hf_specific(
model_path,
cache_dir=None,
allow_patterns=["flownet.pkl"],
require_all=True,
)
def _select_torch_device() -> torch.device:
try:
from vllm_omni.platforms import current_omni_platform
return current_omni_platform.get_torch_device()
except Exception as exc:
logger.warning("Failed to resolve current vLLM-Omni torch device: %s", exc)
if torch.cuda.is_available():
return torch.device("cuda")
return torch.device("cpu")
def _normalize_video_tensor_layout(video: torch.Tensor) -> tuple[torch.Tensor, Any]:
if video.ndim == 5:
if video.shape[1] in (3, 4):
return video, lambda out: out
if video.shape[2] in (3, 4):
return video.permute(0, 2, 1, 3, 4), lambda out: out.permute(0, 2, 1, 3, 4)
elif video.ndim == 4:
if video.shape[0] in (3, 4):
return video.unsqueeze(0), lambda out: out.squeeze(0)
if video.shape[1] in (3, 4):
return video.permute(1, 0, 2, 3).unsqueeze(0), lambda out: out.squeeze(0).permute(1, 0, 2, 3)
raise ValueError(f"Unsupported video tensor shape for interpolation: {tuple(video.shape)}")
def _normalize_video_tensor_range(video: torch.Tensor) -> tuple[torch.Tensor, Any]:
original_dtype = video.dtype
video = video.detach()
if video.is_floating_point():
video = video.to(torch.float32)
if torch.amin(video) < 0.0 or torch.amax(video) > 1.0:
return video.clamp(-1.0, 1.0) * 0.5 + 0.5, lambda out: (out * 2.0 - 1.0).to(original_dtype)
return video.clamp(0.0, 1.0), lambda out: out.to(original_dtype)
return video.to(torch.float32) / 255.0, lambda out: (out * 255.0).round().clamp(0, 255).to(original_dtype)
class FrameInterpolator:
"""Lazy-loaded RIFE 4.22.lite frame interpolator."""
def __init__(self, model_path: str | None = None):
self._model_path = model_path
self._resolved_path: str | None = None
def _ensure_model_loaded(self, preferred_device: torch.device | None = None) -> Model:
resolved_path = _resolve_rife_model_path(self._model_path)
self._resolved_path = resolved_path
device = preferred_device or _select_torch_device()
cache_key = (resolved_path, str(device))
with _MODEL_CACHE_LOCK:
if cache_key in _MODEL_CACHE:
return _MODEL_CACHE[cache_key]
model = Model()
model.load_model(resolved_path)
model.eval()
model.flownet = model.flownet.to(device)
_MODEL_CACHE[cache_key] = model
logger.info("RIFE model loaded on device: %s", device)
return model
def _make_inference(
self,
model: Model,
img0: torch.Tensor,
img1: torch.Tensor,
n: int,
scale: float,
) -> list[torch.Tensor]:
if n == 1:
return [model.inference(img0, img1, scale=scale)]
mid = model.inference(img0, img1, scale=scale)
return (
self._make_inference(model, img0, mid, n // 2, scale)
+ [mid]
+ self._make_inference(model, mid, img1, n // 2, scale)
)
def interpolate_tensor(
self,
video: torch.Tensor,
exp: int = 1,
scale: float = 1.0,
) -> tuple[torch.Tensor, int]:
if exp < 1:
raise ValueError(f"frame interpolation exp must be >= 1, got {exp}")
if scale <= 0:
raise ValueError(f"frame interpolation scale must be > 0, got {scale}")
video, restore_layout = _normalize_video_tensor_layout(video)
if video.shape[2] < 2:
return restore_layout(video), 1
video, restore_range = _normalize_video_tensor_range(video)
# A CPU tensor may be transport/offload state rather than an execution
# choice, so only trust it when it is already on an accelerator.
preferred_device = video.device
if preferred_device.type == "cpu":
preferred_device = _select_torch_device()
model = self._ensure_model_loaded(preferred_device=preferred_device)
video = video.to(model.device())
intermediates_per_pair = 2**exp // 2
result_frames: list[torch.Tensor] = []
for idx in range(video.shape[2] - 1):
img0 = video[:, :, idx, :, :]
img1 = video[:, :, idx + 1, :, :]
result_frames.append(img0)
result_frames.extend(self._make_inference(model, img0, img1, intermediates_per_pair, scale))
result_frames.append(video[:, :, -1, :, :])
result = torch.stack(result_frames, dim=2)
return restore_layout(restore_range(result)), 2**exp
def interpolate_video_tensor(
video: torch.Tensor,
exp: int = 1,
scale: float = 1.0,
model_path: str | None = None,
) -> tuple[torch.Tensor, int]:
"""Interpolate a video tensor and return the FPS multiplier."""
interpolator = FrameInterpolator(model_path=model_path)
return interpolator.interpolate_tensor(video, exp=exp, scale=scale)