IMOFC: Identity-Level Metric Optimized Feature Compression for Identification Tasks

Feature compression has attracted much attention in recent years due to its promising applications in scenarios where features are transmitted and analyzed by machine vision. However, existing research mainly focuses on coarse-grained features extracted from recognition tasks such as classification and detection, neglecting fine-grained features extracted from identification tasks. In this paper, we make a pioneering attempt to study fine-grained feature compression in the context of identification tasks. Our main focus is on the distortion metric, given its critical importance in optimizing the performance of a compression network. We initiate our discussion by reviewing the instance-level metrics in existing literature, highlighting their oversight of the inter-feature relationships. The inter-feature relationships are especially important for identification tasks as they involve similarity comparison among different identities. To address this problem, we propose to consider inter-feature relationships from the perspective of identity information. Specifically, we propose an identity-level metric to incorporate both intra-identity similarity and inter-identity discriminability. The intra-identity similarity constraint aims to cluster features from the same identity, while the inter-identity discriminability constraint ensures that features from different identities deviate from each other. We implement the identity-level metric on four different feature compression networks designed based on feature characteristics. Experimental results show the effectiveness of the proposed identity-level metric on person re-identification and face verification tasks.