FastVLM: Efficient Vision Encoding for Vision Language Models (2412.13303v1)

Abstract: Scaling the input image resolution is essential for enhancing the performance of Vision LLMs (VLMs), particularly in text-rich image understanding tasks. However, popular visual encoders such as ViTs become inefficient at high resolutions due to the large number of tokens and high encoding latency caused by stacked self-attention layers. At different operational resolutions, the vision encoder of a VLM can be optimized along two axes: reducing encoding latency and minimizing the number of visual tokens passed to the LLM, thereby lowering overall latency. Based on a comprehensive efficiency analysis of the interplay between image resolution, vision latency, token count, and LLM size, we introduce FastVLM, a model that achieves an optimized trade-off between latency, model size and accuracy. FastVLM incorporates FastViTHD, a novel hybrid vision encoder designed to output fewer tokens and significantly reduce encoding time for high-resolution images. Unlike previous methods, FastVLM achieves the optimal balance between visual token count and image resolution solely by scaling the input image, eliminating the need for additional token pruning and simplifying the model design. In the LLaVA-1.5 setup, FastVLM achieves 3.2$\times$ improvement in time-to-first-token (TTFT) while maintaining similar performance on VLM benchmarks compared to prior works. Compared to LLaVa-OneVision at the highest resolution (1152$\times$1152), FastVLM achieves comparable performance on key benchmarks like SeedBench and MMMU, using the same 0.5B LLM, but with 85$\times$ faster TTFT and a vision encoder that is 3.4$\times$ smaller.

An Analytical Overview of FastVLM: Efficient Vision Encoding for Vision LLMs

The paper "FastVLM: Efficient Vision Encoding for Vision LLMs" presents a comprehensive paper on improving the efficiency of Vision LLMs (VLMs) by introducing an innovative vision encoder named FastVLM, built upon the novel FastViTHD architecture. This research focuses on addressing the latency issues associated with processing high-resolution images in VLMs, which are critical for text-rich image understanding tasks. The authors offer a new perspective on optimizing VLM performance by crafting an encoder capable of managing high-resolution images with reduced time-to-first-token (TTFT) and fewer parameters, thus providing significant improvements over existing architectures.

The inefficiency of traditional vision encoders, such as Vision Transformers (ViTs), which suffer from high computational demands due to numerous tokens and extensive self-attention layers, serves as a key motivation for this work. The proposed solution, FastVLM, optimizes across latency, accuracy, and model size by employing a hybrid architecture. FastViTHD distinguishes itself by greatly reducing the number of tokens through effective multi-scale pooling and structural modifications, providing a substantial advantage in reducing latency and computational load.

Key Contributions and Results

1. Hybrid Vision Encoder: FastViTHD combines the strengths of convolutional and transformer architectures to efficiently process high-resolution images. By reducing the number of visual tokens the encoder generates, it decreases the prefilling time needed for LLMs.
2. Benchmark Comparisons: The paper details strong comparative performance of FastVLM against existing models. Notably, FastVLM achieves a 3.2× improvement in TTFT while maintaining comparable accuracy on standard VLM benchmarks such as SeedBench and MMCU when compared to LLaVA-OneVision at 1152x1152 resolution, doing so with an encoder that is 3.4× smaller and 85× faster.
3. Resolution Scaling Strategy: FastVLM effectively scales with input resolution without relying on token pruning, unlike other architectures. This natural scaling is enabled by the encoder's design, which simplifies model complexity and operational logistics.
4. Empirical Evaluation: The performance of FastVLM is extensively validated using a variety of benchmark tasks including general knowledge (GQA), text-rich tasks (TextVQA, DocVQA), and speed/efficiency benchmarks, demonstrating its utility across diverse application scenarios.

Implications and Future Directions

The introduction of FastVLM has significant implications for the deployment of VLMs in real-world applications where computational resources may be limited or when on-device processing is critical. The marked reduction in TTFT and visual token generation without sacrificing accuracy paves the way for more scalable and efficient AI systems. Practitioners and developers can leverage these advancements to deploy VLMs in more constrained environments or applications requiring rapid visual recognition and reasoning capabilities.

Furthermore, the principles explored in this paper can seed future research in designing architectures that balance precision and computational efficiency, particularly as the demand for processing higher-resolution visual data continues to grow. Future exploration could expand upon modular hybrid models that are capable of dynamically adjusting their depth or breadth based on the task specificity, further aligning computational costs with the complexity and needs of the workload.

Through a rigorous efficiency-driven analysis and innovation in architectural design, this paper offers a substantive contribution to the development of more accessible, high-performance vision LLMs. FastVLM stands as a promising advancement towards reconciling the demands of high-resolution image processing with the operational constraints of modern AI systems.