description: Discover SAM 2, the next generation of Meta's Segment Anything Model, supporting real-time promptable segmentation in both images and videos with state-of-the-art performance. Learn about its key features, datasets, and how to use it.
SAM 2, the successor to Meta's [Segment Anything Model (SAM)](sam.md), is a cutting-edge tool designed for comprehensive object segmentation in both images and videos. It excels in handling complex visual data through a unified, promptable model architecture that supports real-time processing and zero-shot generalization.
SAM 2 combines the capabilities of image and video segmentation in a single model. This unification simplifies deployment and allows for consistent performance across different media types. It leverages a flexible prompt-based interface, enabling users to specify objects of interest through various prompt types, such as points, bounding boxes, or masks.
The model achieves real-time inference speeds, processing approximately 44 frames per second. This makes SAM 2 suitable for applications requiring immediate feedback, such as video editing and augmented reality.
SAM 2 can segment objects it has never encountered before, demonstrating strong zero-shot generalization. This is particularly useful in diverse or evolving visual domains where pre-defined categories may not cover all possible objects.
Users can iteratively refine the segmentation results by providing additional prompts, allowing for precise control over the output. This interactivity is essential for fine-tuning results in applications like video annotation or medical imaging.
SAM 2 includes mechanisms to manage common video segmentation challenges, such as object occlusion and reappearance. It uses a sophisticated memory mechanism to keep track of objects across frames, ensuring continuity even when objects are temporarily obscured or exit and re-enter the scene.
| **Image Segmentation Accuracy** | **Improved** | SAM |
| **Inference Speed** | **6x faster** | SAM |
## Model Architecture
### Core Components
- **Image and Video Encoder**: Utilizes a transformer-based architecture to extract high-level features from both images and video frames. This component is responsible for understanding the visual content at each timestep.
- **Prompt Encoder**: Processes user-provided prompts (points, boxes, masks) to guide the segmentation task. This allows SAM 2 to adapt to user input and target specific objects within a scene.
- **Memory Mechanism**: Includes a memory encoder, memory bank, and memory attention module. These components collectively store and utilize information from past frames, enabling the model to maintain consistent object tracking over time.
- **Mask Decoder**: Generates the final segmentation masks based on the encoded image features and prompts. In video, it also uses memory context to ensure accurate tracking across frames.
The memory mechanism allows SAM 2 to handle temporal dependencies and occlusions in video data. As objects move and interact, SAM 2 records their features in a memory bank. When an object becomes occluded, the model can rely on this memory to predict its position and appearance when it reappears. The occlusion head specifically handles scenarios where objects are not visible, predicting the likelihood of an object being occluded.
In situations with ambiguity (e.g., overlapping objects), SAM 2 can generate multiple mask predictions. This feature is crucial for accurately representing complex scenes where a single mask might not sufficiently describe the scene's nuances.
- **51,000+ Videos**: Captured across 47 countries, providing a wide range of real-world scenarios.
- **600,000+ Mask Annotations**: Detailed spatio-temporal mask annotations, referred to as "masklets," covering whole objects and parts.
- **Dataset Scale**: It features 4.5 times more videos and 53 times more annotations than previous largest datasets, offering unprecedented diversity and complexity.
The following table details the available SAM 2 models, their pre-trained weights, supported tasks, and compatibility with different operating modes like [Inference](../modes/predict.md), [Validation](../modes/val.md), [Training](../modes/train.md), and [Export](../modes/export.md).
SAM 2 can be utilized across a broad spectrum of tasks, including real-time video editing, medical imaging, and autonomous systems. Its ability to segment both static and dynamic visual data makes it a versatile tool for researchers and developers.
This comparison shows the order-of-magnitude differences in the model sizes and speeds between models. Whereas SAM presents unique capabilities for automatic segmenting, it is not a direct competitor to YOLOv8 segment models, which are smaller, faster and more efficient.
Auto-annotation is a powerful feature of SAM 2, enabling users to generate segmentation datasets quickly and accurately by leveraging pre-trained models. This capability is particularly useful for creating large, high-quality datasets without extensive manual effort.
| `device` | `str`, optional | Device to run the models on. Defaults to an empty string (CPU or GPU, if available). | |
| `output_dir` | `str`, `None`, optional | Directory to save the annotated results. Defaults to a 'labels' folder in the same directory as 'data'. | `None` |
This function facilitates the rapid creation of high-quality segmentation datasets, ideal for researchers and developers aiming to accelerate their projects.
- **Object Confusion**: The model can sometimes confuse similar-looking objects, particularly in crowded scenes.
- **Efficiency with Multiple Objects**: Segmentation efficiency decreases when processing multiple objects simultaneously due to the lack of inter-object communication.
- **Detail Accuracy**: May miss fine details, especially with fast-moving objects. Additional prompts can partially address this issue, but temporal smoothness is not guaranteed.
title={SAM 2: Segment Anything in Images and Videos},
author={Ravi, Nikhila and Gabeur, Valentin and Hu, Yuan-Ting and Hu, Ronghang and Ryali, Chaitanya and Ma, Tengyu and Khedr, Haitham and R{\"a}dle, Roman and Rolland, Chloe and Gustafson, Laura and Mintun, Eric and Pan, Junting and Alwala, Kalyan Vasudev and Carion, Nicolas and Wu, Chao-Yuan and Girshick, Ross and Doll{\'a}r, Piotr and Feichtenhofer, Christoph},
SAM 2, the successor to Meta's [Segment Anything Model (SAM)](sam.md), is a cutting-edge tool designed for comprehensive object segmentation in both images and videos. It excels in handling complex visual data through a unified, promptable model architecture that supports real-time processing and zero-shot generalization. SAM 2 offers several improvements over the original SAM, including:
SAM 2 can be utilized for real-time video segmentation by leveraging its promptable interface and real-time inference capabilities. Here's a basic example:
- **51,000+ Videos**: Captured across 47 countries, providing a wide range of real-world scenarios.
- **600,000+ Mask Annotations**: Detailed spatio-temporal mask annotations, referred to as "masklets," covering whole objects and parts.
- **Dataset Scale**: Features 4.5 times more videos and 53 times more annotations than previous largest datasets, offering unprecedented diversity and complexity.
This extensive dataset allows SAM 2 to achieve superior performance across major video segmentation benchmarks and enhances its zero-shot generalization capabilities. For more information, see the [SA-V Dataset](#sa-v-dataset) section.
- **Memory Encoder and Memory Bank**: Stores features from past frames.
- **Memory Attention Module**: Utilizes stored information to maintain consistent object tracking over time.
- **Occlusion Head**: Specifically handles scenarios where objects are not visible, predicting the likelihood of an object being occluded.
This mechanism ensures continuity even when objects are temporarily obscured or exit and re-enter the scene. For more details, refer to the [Memory Mechanism and Occlusion Handling](#memory-mechanism-and-occlusion-handling) section.
SAM 2 and Ultralytics YOLOv8 serve different purposes and excel in different areas. While SAM 2 is designed for comprehensive object segmentation with advanced features like zero-shot generalization and real-time performance, YOLOv8 is optimized for speed and efficiency in object detection and segmentation tasks. Here's a comparison:
