vllm/docs/source/usage/multimodal_inputs.rst

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.. _multimodal_inputs:
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Multimodal Inputs
=================
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This page teaches you how to pass multi-modal inputs to :ref:`multi-modal models <supported_mm_models>` in vLLM.
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.. note::
We are actively iterating on multi-modal support. See `this RFC <https://github.com/vllm-project/vllm/issues/4194>`_ for upcoming changes,
and `open an issue on GitHub <https://github.com/vllm-project/vllm/issues/new/choose>`_ if you have any feedback or feature requests.
Offline Inference
-----------------
To input multi-modal data, follow this schema in :class:`vllm.inputs.PromptType`:
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* ``prompt``: The prompt should follow the format that is documented on HuggingFace.
* ``multi_modal_data``: This is a dictionary that follows the schema defined in :class:`vllm.multimodal.MultiModalDataDict`.
Image
^^^^^
You can pass a single image to the :code:`'image'` field of the multi-modal dictionary, as shown in the following examples:
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.. code-block:: python
llm = LLM(model="llava-hf/llava-1.5-7b-hf")
# Refer to the HuggingFace repo for the correct format to use
prompt = "USER: <image>\nWhat is the content of this image?\nASSISTANT:"
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# Load the image using PIL.Image
image = PIL.Image.open(...)
# Single prompt inference
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outputs = llm.generate({
"prompt": prompt,
"multi_modal_data": {"image": image},
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})
for o in outputs:
generated_text = o.outputs[0].text
print(generated_text)
# Batch inference
image_1 = PIL.Image.open(...)
image_2 = PIL.Image.open(...)
outputs = llm.generate(
[
{
"prompt": "USER: <image>\nWhat is the content of this image?\nASSISTANT:",
"multi_modal_data": {"image": image_1},
},
{
"prompt": "USER: <image>\nWhat's the color of this image?\nASSISTANT:",
"multi_modal_data": {"image": image_2},
}
]
)
for o in outputs:
generated_text = o.outputs[0].text
print(generated_text)
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A code example can be found in `examples/offline_inference_vision_language.py <https://github.com/vllm-project/vllm/blob/main/examples/offline_inference_vision_language.py>`_.
To substitute multiple images inside the same text prompt, you can pass in a list of images instead:
.. code-block:: python
llm = LLM(
model="microsoft/Phi-3.5-vision-instruct",
trust_remote_code=True, # Required to load Phi-3.5-vision
max_model_len=4096, # Otherwise, it may not fit in smaller GPUs
limit_mm_per_prompt={"image": 2}, # The maximum number to accept
)
# Refer to the HuggingFace repo for the correct format to use
prompt = "<|user|>\n<|image_1|>\n<|image_2|>\nWhat is the content of each image?<|end|>\n<|assistant|>\n"
# Load the images using PIL.Image
image1 = PIL.Image.open(...)
image2 = PIL.Image.open(...)
outputs = llm.generate({
"prompt": prompt,
"multi_modal_data": {
"image": [image1, image2]
},
})
for o in outputs:
generated_text = o.outputs[0].text
print(generated_text)
A code example can be found in `examples/offline_inference_vision_language_multi_image.py <https://github.com/vllm-project/vllm/blob/main/examples/offline_inference_vision_language_multi_image.py>`_.
Multi-image input can be extended to perform video captioning. We show this with `Qwen2-VL <https://huggingface.co/Qwen/Qwen2-VL-2B-Instruct>`_ as it supports videos:
.. code-block:: python
# Specify the maximum number of frames per video to be 4. This can be changed.
llm = LLM("Qwen/Qwen2-VL-2B-Instruct", limit_mm_per_prompt={"image": 4})
# Create the request payload.
video_frames = ... # load your video making sure it only has the number of frames specified earlier.
message = {
"role": "user",
"content": [
{"type": "text", "text": "Describe this set of frames. Consider the frames to be a part of the same video."},
],
}
for i in range(len(video_frames)):
base64_image = encode_image(video_frames[i]) # base64 encoding.
new_image = {"type": "image_url", "image_url": {"url": f"data:image/jpeg;base64,{base64_image}"}}
message["content"].append(new_image)
# Perform inference and log output.
outputs = llm.chat([message])
for o in outputs:
generated_text = o.outputs[0].text
print(generated_text)
Video
^^^^^
You can pass a list of NumPy arrays directly to the :code:`'video'` field of the multi-modal dictionary
instead of using multi-image input.
Please refer to `examples/offline_inference_vision_language.py <https://github.com/vllm-project/vllm/blob/main/examples/offline_inference_vision_language.py>`_ for more details.
Audio
^^^^^
You can pass a tuple :code:`(array, sampling_rate)` to the :code:`'audio'` field of the multi-modal dictionary.
Please refer to `examples/offline_inference_audio_language.py <https://github.com/vllm-project/vllm/blob/main/examples/offline_inference_audio_language.py>`_ for more details.
Embedding
^^^^^^^^^
To input pre-computed embeddings belonging to a data type (i.e. image, video, or audio) directly to the language model,
pass a tensor of shape :code:`(num_items, feature_size, hidden_size of LM)` to the corresponding field of the multi-modal dictionary.
.. code-block:: python
# Inference with image embeddings as input
llm = LLM(model="llava-hf/llava-1.5-7b-hf")
# Refer to the HuggingFace repo for the correct format to use
prompt = "USER: <image>\nWhat is the content of this image?\nASSISTANT:"
# Embeddings for single image
# torch.Tensor of shape (1, image_feature_size, hidden_size of LM)
image_embeds = torch.load(...)
outputs = llm.generate({
"prompt": prompt,
"multi_modal_data": {"image": image_embeds},
})
for o in outputs:
generated_text = o.outputs[0].text
print(generated_text)
For Qwen2-VL and MiniCPM-V, we accept additional parameters alongside the embeddings:
.. code-block:: python
# Construct the prompt based on your model
prompt = ...
# Embeddings for multiple images
# torch.Tensor of shape (num_images, image_feature_size, hidden_size of LM)
image_embeds = torch.load(...)
# Qwen2-VL
llm = LLM("Qwen/Qwen2-VL-2B-Instruct", limit_mm_per_prompt={"image": 4})
mm_data = {
"image": {
"image_embeds": image_embeds,
# image_grid_thw is needed to calculate positional encoding.
"image_grid_thw": torch.load(...), # torch.Tensor of shape (1, 3),
}
}
# MiniCPM-V
llm = LLM("openbmb/MiniCPM-V-2_6", trust_remote_code=True, limit_mm_per_prompt={"image": 4})
mm_data = {
"image": {
"image_embeds": image_embeds,
# image_size_list is needed to calculate details of the sliced image.
"image_size_list": [image.size for image in images], # list of image sizes
}
}
outputs = llm.generate({
"prompt": prompt,
"multi_modal_data": mm_data,
})
for o in outputs:
generated_text = o.outputs[0].text
print(generated_text)
Online Inference
----------------
Our OpenAI-compatible server accepts multi-modal data via the `Chat Completions API <https://platform.openai.com/docs/api-reference/chat>`_.
.. important::
A chat template is **required** to use Chat Completions API.
Although most models come with a chat template, for others you have to define one yourself.
The chat template can be inferred based on the documentation on the model's HuggingFace repo.
For example, LLaVA-1.5 (``llava-hf/llava-1.5-7b-hf``) requires a chat template that can be found `here <https://github.com/vllm-project/vllm/blob/main/examples/template_llava.jinja>`__.
Image
^^^^^
Image input is supported according to `OpenAI Vision API <https://platform.openai.com/docs/guides/vision>`_.
Here is a simple example using Phi-3.5-Vision.
First, launch the OpenAI-compatible server:
.. code-block:: bash
vllm serve microsoft/Phi-3.5-vision-instruct --task generate \
--trust-remote-code --max-model-len 4096 --limit-mm-per-prompt image=2
Then, you can use the OpenAI client as follows:
.. code-block:: python
from openai import OpenAI
openai_api_key = "EMPTY"
openai_api_base = "http://localhost:8000/v1"
client = OpenAI(
api_key=openai_api_key,
base_url=openai_api_base,
)
# Single-image input inference
image_url = "https://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Gfp-wisconsin-madison-the-nature-boardwalk.jpg/2560px-Gfp-wisconsin-madison-the-nature-boardwalk.jpg"
chat_response = client.chat.completions.create(
model="microsoft/Phi-3.5-vision-instruct",
messages=[{
"role": "user",
"content": [
# NOTE: The prompt formatting with the image token `<image>` is not needed
# since the prompt will be processed automatically by the API server.
{"type": "text", "text": "Whats in this image?"},
{"type": "image_url", "image_url": {"url": image_url}},
],
}],
)
print("Chat completion output:", chat_response.choices[0].message.content)
# Multi-image input inference
image_url_duck = "https://upload.wikimedia.org/wikipedia/commons/d/da/2015_Kaczka_krzy%C5%BCowka_w_wodzie_%28samiec%29.jpg"
image_url_lion = "https://upload.wikimedia.org/wikipedia/commons/7/77/002_The_lion_king_Snyggve_in_the_Serengeti_National_Park_Photo_by_Giles_Laurent.jpg"
chat_response = client.chat.completions.create(
model="microsoft/Phi-3.5-vision-instruct",
messages=[{
"role": "user",
"content": [
{"type": "text", "text": "What are the animals in these images?"},
{"type": "image_url", "image_url": {"url": image_url_duck}},
{"type": "image_url", "image_url": {"url": image_url_lion}},
],
}],
)
print("Chat completion output:", chat_response.choices[0].message.content)
A full code example can be found in `examples/openai_chat_completion_client_for_multimodal.py <https://github.com/vllm-project/vllm/blob/main/examples/openai_chat_completion_client_for_multimodal.py>`_.
.. tip::
Loading from local file paths is also supported on vLLM: You can specify the allowed local media path via ``--allowed-local-media-path`` when launching the API server/engine,
and pass the file path as ``url`` in the API request.
.. tip::
There is no need to place image placeholders in the text content of the API request - they are already represented by the image content.
In fact, you can place image placeholders in the middle of the text by interleaving text and image content.
.. note::
By default, the timeout for fetching images through HTTP URL is ``5`` seconds.
You can override this by setting the environment variable:
.. code-block:: console
$ export VLLM_IMAGE_FETCH_TIMEOUT=<timeout>
Video
^^^^^
Instead of :code:`image_url`, you can pass a video file via :code:`video_url`.
You can use `these tests <https://github.com/vllm-project/vllm/blob/main/tests/entrypoints/openai/test_video.py>`_ as reference.
.. note::
By default, the timeout for fetching videos through HTTP URL url is ``30`` seconds.
You can override this by setting the environment variable:
.. code-block:: console
$ export VLLM_VIDEO_FETCH_TIMEOUT=<timeout>
Audio
^^^^^
Instead of :code:`image_url`, you can pass an audio file via :code:`audio_url`.
A full code example can be found in `examples/openai_chat_completion_client_for_multimodal.py <https://github.com/vllm-project/vllm/blob/main/examples/openai_chat_completion_client_for_multimodal.py>`_.
.. note::
By default, the timeout for fetching audios through HTTP URL is ``10`` seconds.
You can override this by setting the environment variable:
.. code-block:: console
$ export VLLM_AUDIO_FETCH_TIMEOUT=<timeout>
Embedding
^^^^^^^^^
vLLM's Embeddings API is a superset of OpenAI's `Embeddings API <https://platform.openai.com/docs/api-reference/embeddings>`_,
where a list of chat ``messages`` can be passed instead of batched ``inputs``. This enables multi-modal inputs to be passed to embedding models.
.. tip::
The schema of ``messages`` is exactly the same as in Chat Completions API.
You can refer to the above tutorials for more details on how to pass each type of multi-modal data.
Usually, embedding models do not expect chat-based input, so we need to use a custom chat template to format the text and images.
Refer to the examples below for illustration.
Here is an end-to-end example using VLM2Vec. To serve the model:
.. code-block:: bash
vllm serve TIGER-Lab/VLM2Vec-Full --task embed \
--trust-remote-code --max-model-len 4096 --chat-template examples/template_vlm2vec.jinja
.. important::
Since VLM2Vec has the same model architecture as Phi-3.5-Vision, we have to explicitly pass ``--task embed``
to run this model in embedding mode instead of text generation mode.
The custom chat template is completely different from the original one for this model,
and can be found `here <https://github.com/vllm-project/vllm/blob/main/examples/template_vlm2vec.jinja>`__.
Since the request schema is not defined by OpenAI client, we post a request to the server using the lower-level ``requests`` library:
.. code-block:: python
import requests
image_url = "https://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Gfp-wisconsin-madison-the-nature-boardwalk.jpg/2560px-Gfp-wisconsin-madison-the-nature-boardwalk.jpg"
response = requests.post(
"http://localhost:8000/v1/embeddings",
json={
"model": "TIGER-Lab/VLM2Vec-Full",
"messages": [{
"role": "user",
"content": [
{"type": "image_url", "image_url": {"url": image_url}},
{"type": "text", "text": "Represent the given image."},
],
}],
"encoding_format": "float",
},
)
response.raise_for_status()
response_json = response.json()
print("Embedding output:", response_json["data"][0]["embedding"])
Below is another example, this time using the ``MrLight/dse-qwen2-2b-mrl-v1`` model.
.. code-block:: bash
vllm serve MrLight/dse-qwen2-2b-mrl-v1 --task embed \
--trust-remote-code --max-model-len 8192 --chat-template examples/template_dse_qwen2_vl.jinja
.. important::
Like with VLM2Vec, we have to explicitly pass ``--task embed``.
Additionally, ``MrLight/dse-qwen2-2b-mrl-v1`` requires an EOS token for embeddings, which is handled
by `this custom chat template <https://github.com/vllm-project/vllm/blob/main/examples/template_dse_qwen2_vl.jinja>`__.
.. important::
Also important, ``MrLight/dse-qwen2-2b-mrl-v1`` requires a placeholder image of the minimum image size for text query embeddings. See the full code
example below for details.
A full code example can be found in `examples/openai_chat_embedding_client_for_multimodal.py <https://github.com/vllm-project/vllm/blob/main/examples/openai_chat_embedding_client_for_multimodal.py>`_.