Remote VAEs for decoding with Inference Endpoints 🤗

Published February 24, 2025
Update on GitHub

When operating with latent-space diffusion models for high-resolution image and video synthesis, the VAE decoder can consume quite a bit more memory. This makes it hard for the users to run these models on consumer GPUs without going through latency sacrifices and others alike.

For example, with offloading, there is a device transfer overhead, causing delays in the overall inference latency. Tiling is another solution that lets us operate on so-called “tiles” of inputs. However, it can have a negative impact on the quality of the final image.

Therefore, we want to pilot an idea with the community — delegating the decoding process to a remote endpoint.

No data is stored or tracked, and code is open source. We made some changes to huggingface-inference-toolkit and use custom handlers.

Table of contents:

Getting started

Below, we cover three use cases where we think this remote VAE inference would be beneficial.

Code

First, we have created a helper method for interacting with Remote VAEs.

Code

from typing import cast, List, Literal, Optional, Union

import base64
import io
import json
import requests
import torch
from PIL import Image

from diffusers.image_processor import VaeImageProcessor
from diffusers.video_processor import VideoProcessor
from safetensors.torch import _tobytes

DTYPE_MAP = {
    "float16": torch.float16,
    "float32": torch.float32,
    "bfloat16": torch.bfloat16,
    "uint8": torch.uint8,
}


def remote_decode(
    endpoint: str,
    tensor: torch.Tensor,
    processor: Optional[Union[VaeImageProcessor, VideoProcessor]] = None,
    do_scaling: bool = True,
    output_type: Literal["mp4", "pil", "pt"] = "pil",
    image_format: Literal["png", "jpg"] = "jpg",
    partial_postprocess: bool = False,
    input_tensor_type: Literal["base64", "binary"] = "base64",
    output_tensor_type: Literal["base64", "binary"] = "base64",
    height: Optional[int] = None,
    width: Optional[int] = None,
) -> Union[Image.Image, List[Image.Image], bytes, torch.Tensor]:
    if tensor.ndim == 3 and height is None and width is None:
        raise ValueError("`height` and `width` required for packed latents.")
    if output_type == "pt" and partial_postprocess is False and processor is None:
        raise ValueError(
            "`processor` is required with `output_type='pt' and `partial_postprocess=False`."
        )
    headers = {}
    parameters = {
        "do_scaling": do_scaling,
        "output_type": output_type,
        "partial_postprocess": partial_postprocess,
        "shape": list(tensor.shape),
        "dtype": str(tensor.dtype).split(".")[-1],
    }
    if height is not None and width is not None:
        parameters["height"] = height
        parameters["width"] = width
    tensor_data = _tobytes(tensor, "tensor")
    if input_tensor_type == "base64":
        headers["Content-Type"] = "tensor/base64"
    elif input_tensor_type == "binary":
        headers["Content-Type"] = "tensor/binary"
    if output_type == "pil" and image_format == "jpg" and processor is None:
        headers["Accept"] = "image/jpeg"
    elif output_type == "pil" and image_format == "png" and processor is None:
        headers["Accept"] = "image/png"
    elif (output_tensor_type == "base64" and output_type == "pt") or (
        output_tensor_type == "base64"
        and output_type == "pil"
        and processor is not None
    ):
        headers["Accept"] = "tensor/base64"
    elif (output_tensor_type == "binary" and output_type == "pt") or (
        output_tensor_type == "binary"
        and output_type == "pil"
        and processor is not None
    ):
        headers["Accept"] = "tensor/binary"
    elif output_type == "mp4":
        headers["Accept"] = "text/plain"
    if input_tensor_type == "base64":
        kwargs = {"json": {"inputs": base64.b64encode(tensor_data).decode("utf-8")}}
    elif input_tensor_type == "binary":
        kwargs = {"data": tensor_data}
    response = requests.post(endpoint, params=parameters, **kwargs, headers=headers)
    if not response.ok:
        raise RuntimeError(response.json())
    if output_type == "pt" or (output_type == "pil" and processor is not None):
        if output_tensor_type == "base64":
            content = response.json()
            output_tensor = base64.b64decode(content["inputs"])
            parameters = content["parameters"]
            shape = parameters["shape"]
            dtype = parameters["dtype"]
        elif output_tensor_type == "binary":
            output_tensor = response.content
            parameters = response.headers
            shape = json.loads(parameters["shape"])
            dtype = parameters["dtype"]
        torch_dtype = DTYPE_MAP[dtype]
        output_tensor = torch.frombuffer(
            bytearray(output_tensor), dtype=torch_dtype
        ).reshape(shape)
    if output_type == "pt":
        if partial_postprocess:
            output = [Image.fromarray(image.numpy()) for image in output_tensor]
            if len(output) == 1:
                output = output[0]
        else:
            if processor is None:
                output = output_tensor
            else:
                if isinstance(processor, VideoProcessor):
                    output = cast(
                        List[Image.Image],
                        processor.postprocess_video(output_tensor, output_type="pil")[0],
                    )
                else:
                    output = cast(
                        Image.Image,
                        processor.postprocess(output_tensor, output_type="pil")[0],
                    )
    elif output_type == "pil" and processor is None:
        output = Image.open(io.BytesIO(response.content)).convert("RGB")
    elif output_type == "pil" and processor is not None:
        output = [
            Image.fromarray(image)
            for image in (output_tensor.permute(0, 2, 3, 1).float().numpy() * 255)
            .round()
            .astype("uint8")
        ]
    elif output_type == "mp4":
        output = response.content
    return output

Basic example

Here, we show how to use the remote VAE on random tensors.

Code

image = remote_decode(
    endpoint="https://q1bj3bpq6kzilnsu.us-east-1.aws.endpoints.huggingface.cloud/",
    tensor=torch.randn([1, 4, 64, 64], dtype=torch.float16),
)

Usage for Flux is slightly different. Flux latents are packed so we need to send the height and width.

Code

image = remote_decode(
    endpoint="https://whhx50ex1aryqvw6.us-east-1.aws.endpoints.huggingface.cloud/",
    tensor=torch.randn([1, 4096, 64], dtype=torch.float16),
    height=1024,
    width=1024,
)

Finally, an example for HunyuanVideo.

Code

video = remote_decode(
    endpoint="https://o7ywnmrahorts457.us-east-1.aws.endpoints.huggingface.cloud/",
    tensor=torch.randn([1, 16, 3, 40, 64], dtype=torch.float16),
    output_type="mp4",
)
with open("video.mp4", "wb") as f:
    f.write(video)

Options

Let's review the available options.

def remote_decode(
    endpoint: str,
    tensor: torch.Tensor,
    processor: Optional[Union[VaeImageProcessor, VideoProcessor]] = None,
    do_scaling: bool = True,
    output_type: Literal["mp4", "pil", "pt"] = "pil",
    image_format: Literal["png", "jpg"] = "jpg",
    partial_postprocess: bool = False,
    input_tensor_type: Literal["base64", "binary"] = "base64",
    output_tensor_type: Literal["base64", "binary"] = "base64",
    height: Optional[int] = None,
    width: Optional[int] = None,
) -> Union[Image.Image, List[Image.Image], bytes, torch.Tensor]:

Overview of decoding

There are 3 parts of decoding in a pipeline: scaling -> decode -> postprocess.

Options allow Remote VAE to be compatible with these different stages.

processor

With output_type="pt" the endpoint returns a torch.Tensor before postprocess. The final postprocessing and image creation is done locally.

With output_type="pil" on video models processor=VideoProcessor() is required for some local postprocessing.

do_scaling

  • do_scaling=False allows Remote VAE to work as a drop-in replacement for pipe.vae.decode. Scaling should be applied to input before remote_decode.
  • do_scaling=True scaling is applied by Remote VAE.

output_type

Image models support: pil, pt.

Video models support: mp4, pil, pt.

  • output_type="pil" returns an image according to image_format for Image models and a tensor for Video models (equivalent to postprocess_video(frames, output_type="pt")) which has final postprocessing applied to create the frame images.
  • output_type="pt" with partial_postprocess=False returns a torch.Tensor before postprocess. The final postprocessing and image creation is done locally.
  • output_type="pt" with partial_postprocess=True returns a torch.Tensor with postprocess applied. The final image creation (PIL.Image.fromarray) is done locally. This reduces transfer compared to partial_postprocess=False.
  • output_type="mp4" applies postprocess_video(frames, output_type="pil") then export_to_video and returns bytes of the mp4.

input_tensor_type/output_tensor_type

Choices base64, binary.

Using binary reduces transfer.

image_format

Choices jpg, png.

jpg is faster but lower quality.

height/width

Required for packed latents in Flux. Not required with do_scaling=False as unpack occurs before scaling.

Generation

But we want to use the VAE on an actual pipeline to get an actual image, not random noise. The example below shows how to do it with SD v1.5.

Code

from diffusers import StableDiffusionPipeline

pipe = StableDiffusionPipeline.from_pretrained(
    "stable-diffusion-v1-5/stable-diffusion-v1-5",
    torch_dtype=torch.float16,
    variant="fp16",
    vae=None,
).to("cuda")

prompt = "Strawberry ice cream, in a stylish modern glass, coconut, splashing milk cream and honey, in a gradient purple background, fluid motion, dynamic movement, cinematic lighting, Mysterious"

latent = pipe(
    prompt=prompt,
    output_type="latent",
).images
image = remote_decode(
    endpoint="https://q1bj3bpq6kzilnsu.us-east-1.aws.endpoints.huggingface.cloud/",
    tensor=latent,
)
image.save("test.jpg")

Here’s another example with Flux.

Code

from diffusers import FluxPipeline

pipe = FluxPipeline.from_pretrained(
    "black-forest-labs/FLUX.1-schnell",
    torch_dtype=torch.bfloat16,
    vae=None,
).to("cuda")

prompt = "Strawberry ice cream, in a stylish modern glass, coconut, splashing milk cream and honey, in a gradient purple background, fluid motion, dynamic movement, cinematic lighting, Mysterious"

latent = pipe(
    prompt=prompt,
    guidance_scale=0.0,
    num_inference_steps=4,
    output_type="latent",
).images
image = remote_decode(
    endpoint="https://whhx50ex1aryqvw6.us-east-1.aws.endpoints.huggingface.cloud/"
    tensor=latent,
    height=1024,
    width=1024,
)
image.save("test.jpg")

Here’s an example with HunyuanVideo.

Code

from diffusers import HunyuanVideoPipeline, HunyuanVideoTransformer3DModel

model_id = "hunyuanvideo-community/HunyuanVideo"
transformer = HunyuanVideoTransformer3DModel.from_pretrained(
    model_id, subfolder="transformer", torch_dtype=torch.bfloat16
)
pipe = HunyuanVideoPipeline.from_pretrained(
    model_id, transformer=transformer, vae=None, torch_dtype=torch.float16
).to("cuda")

latent = pipe(
    prompt="A cat walks on the grass, realistic",
    height=320,
    width=512,
    num_frames=61,
    num_inference_steps=30,
    output_type="latent",
).frames

video = remote_decode(
    endpoint="https://o7ywnmrahorts457.us-east-1.aws.endpoints.huggingface.cloud/",
    tensor=latent,
    output_type="mp4",
)

Queueing

One of the great benefits of using a remote VAE is that we can queue multiple generation requests. While the current latent is being processed for decoding, we can already queue another one. This helps improve concurrency.

Code

import queue
import threading
from IPython.display import display
from diffusers import StableDiffusionPipeline

def decode_worker(q: queue.Queue):
    while True:
        item = q.get()
        if item is None:
            break
        image = remote_decode(
            endpoint="https://q1bj3bpq6kzilnsu.us-east-1.aws.endpoints.huggingface.cloud/",
            tensor=item,
        )
        display(image)
        q.task_done()

q = queue.Queue()
thread = threading.Thread(target=decode_worker, args=(q,), daemon=True)
thread.start()

def decode(latent: torch.Tensor):
    q.put(latent)

prompts = [
    "Blueberry ice cream, in a stylish modern glass , ice cubes, nuts, mint leaves, splashing milk cream, in a gradient purple background, fluid motion, dynamic movement, cinematic lighting, Mysterious",
    "Lemonade in a glass, mint leaves, in an aqua and white background, flowers, ice cubes, halo, fluid motion, dynamic movement, soft lighting, digital painting, rule of third's composition, Art by Greg rutkowski, Coby whitmore",
    "Comic book art, beautiful, vintage, pastel neon colors, extremely detailed pupils, delicate features, light on face, slight smile, Artgerm, Mary Blair, Edmund Dulac, long dark locks, bangs, glowing, fashionable style, fairytale ambience, hot pink.",
    "Masterpiece, vanilla cone ice cream garnished with chocolate syrup, crushed nuts, choco flakes, in a brown background, gold, cinematic lighting, Art by WLOP",
    "A bowl of milk, falling cornflakes, berries, blueberries, in a white background, soft lighting, intricate details, rule of third's, octane render, volumetric lighting",
    "Cold Coffee with cream, crushed almonds, in a glass, choco flakes, ice cubes, wet, in a wooden background, cinematic lighting, hyper realistic painting, art by Carne Griffiths, octane render, volumetric lighting, fluid motion, dynamic movement, muted colors,",
]

pipe = StableDiffusionPipeline.from_pretrained(
    "Lykon/dreamshaper-8",
    torch_dtype=torch.float16,
    vae=None,
).to("cuda")

pipe.unet = pipe.unet.to(memory_format=torch.channels_last)
pipe.unet = torch.compile(pipe.unet, mode="reduce-overhead", fullgraph=True)

_ = pipe(
    prompt=prompts[0],
    output_type="latent",
)

for prompt in prompts:
    latent = pipe(
        prompt=prompt,
        output_type="latent",
    ).images
    decode(latent)

q.put(None)
thread.join()

Available VAEs

Advantages of using a remote VAE

These tables demonstrate the VRAM requirements with different GPUs. Memory usage % determines whether users of a certain GPU will need to offload. Offload times vary with CPU, RAM and HDD/NVMe. Tiled decoding increases inference time.

SD v1.5

GPU Resolution Time (seconds) Memory (%) Tiled Time (secs) Tiled Memory (%)
NVIDIA GeForce RTX 4090 512x512 0.031 5.60% 0.031 (0%) 5.60%
NVIDIA GeForce RTX 4090 1024x1024 0.148 20.00% 0.301 (+103%) 5.60%
NVIDIA GeForce RTX 4080 512x512 0.05 8.40% 0.050 (0%) 8.40%
NVIDIA GeForce RTX 4080 1024x1024 0.224 30.00% 0.356 (+59%) 8.40%
NVIDIA GeForce RTX 4070 Ti 512x512 0.066 11.30% 0.066 (0%) 11.30%
NVIDIA GeForce RTX 4070 Ti 1024x1024 0.284 40.50% 0.454 (+60%) 11.40%
NVIDIA GeForce RTX 3090 512x512 0.062 5.20% 0.062 (0%) 5.20%
NVIDIA GeForce RTX 3090 1024x1024 0.253 18.50% 0.464 (+83%) 5.20%
NVIDIA GeForce RTX 3080 512x512 0.07 12.80% 0.070 (0%) 12.80%
NVIDIA GeForce RTX 3080 1024x1024 0.286 45.30% 0.466 (+63%) 12.90%
NVIDIA GeForce RTX 3070 512x512 0.102 15.90% 0.102 (0%) 15.90%
NVIDIA GeForce RTX 3070 1024x1024 0.421 56.30% 0.746 (+77%) 16.00%

SDXL

GPU Resolution Time (seconds) Memory Consumed (%) Tiled Time (seconds) Tiled Memory (%)
NVIDIA GeForce RTX 4090 512x512 0.057 10.00% 0.057 (0%) 10.00%
NVIDIA GeForce RTX 4090 1024x1024 0.256 35.50% 0.257 (+0.4%) 35.50%
NVIDIA GeForce RTX 4080 512x512 0.092 15.00% 0.092 (0%) 15.00%
NVIDIA GeForce RTX 4080 1024x1024 0.406 53.30% 0.406 (0%) 53.30%
NVIDIA GeForce RTX 4070 Ti 512x512 0.121 20.20% 0.120 (-0.8%) 20.20%
NVIDIA GeForce RTX 4070 Ti 1024x1024 0.519 72.00% 0.519 (0%) 72.00%
NVIDIA GeForce RTX 3090 512x512 0.107 10.50% 0.107 (0%) 10.50%
NVIDIA GeForce RTX 3090 1024x1024 0.459 38.00% 0.460 (+0.2%) 38.00%
NVIDIA GeForce RTX 3080 512x512 0.121 25.60% 0.121 (0%) 25.60%
NVIDIA GeForce RTX 3080 1024x1024 0.524 93.00% 0.524 (0%) 93.00%
NVIDIA GeForce RTX 3070 512x512 0.183 31.80% 0.183 (0%) 31.80%
NVIDIA GeForce RTX 3070 1024x1024 0.794 96.40% 0.794 (0%) 96.40%

Provide feedback

If you like the idea and feature, please help us with your feedback on how we can make this better and whether you’d be interested in having this kind of feature more natively integrated into the Hugging Face ecosystem. If this pilot goes well, we plan on creating optimized VAE endpoints for more models, including the ones that can generate high-resolution videos!

Steps:

  1. Open an issue on Diffusers through this link.
  2. Answer the questions and provide any extra info you want.
  3. Hit submit!

Community

The article is not so clear about some points:

  • "time" does mean "inference time" or "offloading time"
  • what do you mean by tiled memory / tiled time ?
  • is vae tiling always happening ?

Do we need Pro account for this?

Article author

No.

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