A Novel Rate Control Framework for SIFT/SURF Feature Preservation in H.264/AVC Video Compression
This paper presents a novel rate control framework for H.264/Advanced Video Coding-based video coding that improves the preservation of gradient-based features like scale-invariant feature transform or speeded up robust feature compared with the default rate control algorithm in the JM reference software. First, a criterion (matching score) for feature preservation on the basis of the bag-of-features concept is proposed. Then, the matching scores are collected as a function of the quantization parameters and analyzed for different feature types. With this analysis, macroblocks are categorized into different groups before encoding. Our rate control algorithm assigns different quantization parameters to each group according to the importance of the group for feature extraction. The experimental results show that our rate control algorithm achieves the desired target bit rate, and more features are preserved compared with videos encoded using the default rate control. The proposed approach not only improves feature preservation, but also leads to a noticeable performance improvement in a real image retrieval system. The rate control framework proposed in this paper is fully standard compatible.