# Video-Text Retrieval Embedding with BridgeFormer

*author: Jinling Xu*

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## Description

This operator extracts features for video or text with [BridgeFormer](https://arxiv.org/pdf/2201.04850.pdf) which can generate embeddings for text and video by jointly training a video encoder and text encoder to maximize the cosine similarity.


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## Code Example

Load a video from path './demo_video.mp4' to generate a video embedding. 

Read the text 'kids feeding and playing with the horse' to generate a text embedding. 

- Encode video (default):
```python
from towhee.dc2 import pipe, ops, DataCollection

p = (
    pipe.input('video_path') \
        .map('video_path', 'video_frames', ops.video_decode.ffmpeg()) \
        .map('video_frames', 'vec', ops.video_text_embedding.bridge_former(model_name='frozen_model', modality='video')) \
        .output('video_path', 'video_frames', 'vec')
)

DataCollection(p('./demo_video.mp4')).show()
```
<img src="./video_emb_result.png" width="800px"/>

- Encode text:
```python
from towhee.dc2 import pipe, ops, DataCollection

p = (
    pipe.input('text') \
        .map('text', 'vec', ops.video_text_embedding.bridge_former(model_name='frozen_model', modality='text')) \
        .output('text', 'vec')
)

DataCollection(p('kids feeding and playing with the horse')).show()
```
<img src="./text_emb_result.png" width="800px"/>


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## Factory Constructor

Create the operator via the following factory method

***bridge_former(model_name, modality, weight_path)***

**Parameters:**

​   ***model_name:*** *str*

​   The model name of frozen in time. Supported model names: 
- frozen_model
- clip_initialized_model


​   ***modality:*** *str*

​   Which modality(*video* or *text*) is used to generate the embedding. 

​   ***weight_path:*** *str*

​   pretrained model weights path.  

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## Interface

An video-text embedding operator takes a list of [Towhee VideoFrame](link/to/towhee/image/api/doc) or string as input and generate an embedding in ndarray.


**Parameters:**

​	***data:*** *List[towhee.types.Image]*  or *str*

​  The data (list of  Towhee VideoFrame (which is uniform subsampled from a video) or text based on specified modality) to generate embedding.	



**Returns:** *numpy.ndarray*

​   The data embedding extracted by model.