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VMFormer: End-to-End Video Matting with Transformer (2208.12801v2)

Published 26 Aug 2022 in cs.CV

Abstract: Video matting aims to predict the alpha mattes for each frame from a given input video sequence. Recent solutions to video matting have been dominated by deep convolutional neural networks (CNN) for the past few years, which have become the de-facto standard for both academia and industry. However, they have inbuilt inductive bias of locality and do not capture global characteristics of an image due to the CNN-based architectures. They also lack long-range temporal modeling considering computational costs when dealing with feature maps of multiple frames. In this paper, we propose VMFormer: a transformer-based end-to-end method for video matting. It makes predictions on alpha mattes of each frame from learnable queries given a video input sequence. Specifically, it leverages self-attention layers to build global integration of feature sequences with short-range temporal modeling on successive frames. We further apply queries to learn global representations through cross-attention in the transformer decoder with long-range temporal modeling upon all queries. In the prediction stage, both queries and corresponding feature maps are used to make the final prediction of alpha matte. Experiments show that VMFormer outperforms previous CNN-based video matting methods on the composited benchmarks. To our best knowledge, it is the first end-to-end video matting solution built upon a full vision transformer with predictions on the learnable queries. The project is open-sourced at https://chrisjuniorli.github.io/project/VMFormer/

Citations (13)

Summary

  • The paper introduces an end-to-end transformer-based video matting model that outperforms traditional CNN approaches in temporal coherence.
  • It employs a dual-branch architecture with a CNN backbone and transformer encoder-decoder to capture both short- and long-range dynamics.
  • Empirical results show reduced MAD and MSE errors, highlighting improved precision and efficiency for video editing applications.

VMFormer: End-to-End Video Matting with Transformer

The paper introduces VMFormer, an innovative end-to-end video matting solution that leverages transformer architectures to address limitations inherent in traditional CNN-based approaches. The task of video matting involves estimating alpha mattes for each frame in a video sequence to accurately distinguish between foreground and background. This field has significant applications in video editing and production environments, where being able to seamlessly extract subjects from video is crucial.

Motivation and Approach

Historically, CNNs have dominated the video matting landscape. However, they often struggle with capturing the global context of sequences due to their localized receptive fields. This deficiency hampers the performance in tasks requiring long-range temporal coherence. Transforming these methods with transformers, which inherently model global interactions, could offer substantial improvements.

VMFormer comprises two primary branches:

  1. Feature Modeling Branch: Utilizes a CNN-based backbone followed by a transformer encoder. The encoder component incorporates self-attention mechanisms to achieve a global feature integration.
  2. Query Modeling Branch: Employs a transformer decoder to facilitate global interaction between learnable queries and input features via cross-attention mechanisms.

Temporal modeling is achieved through:

  • Short-range Feature-based Temporal Modeling (SFTM): Focuses on recurrent aggregation of feature maps across consecutive frames to enhance consistency.
  • Long-range Query-based Temporal Modeling (LQTM): Adds an attention-based temporal modeling on top of queries to further encapsulate temporal coherence over extended sequences.

Numerical Results and Performance

The paper presents strong empirical evidence demonstrating superior performance of VMFormer over traditional CNN-based models. Specifically, VMFormer exhibits less mean absolute difference (MAD), mean squared error (MSE), and other variance-related metrics in predictions of alpha mattes under various conditions and image resolutions, indicating high precision and temporal consistency.

Implications and Future Work

VMFormer's architecture decisively proves the efficacy of transformers in video matting tasks, achieving competitive real-time processing speeds akin to existing methods while offering enhanced performance in temporal coherence. This advancement highlights the potential for transformers to facilitate computational efficiency and accuracy in video processing tasks without significant computational compromises.

In the spectrum of video matting research, VMFormer is one of the pioneering solutions to employ a full-fledged vision transformer, with predictions rooted in learnable queries. This work may redirect focus in the research community toward further exploration of transformer-based solutions across different video understanding tasks beyond matting. Future research may involve optimizing the model for various video qualities and leveraging transformers to handle even greater resolutions and more complex video sequences while maintaining or enhancing the inference speed.