Auxiliary Cross-Modal Representation Learning with Triplet Loss Functions for Online Handwriting Recognition

TL;DR

This paper introduces a triplet loss-based cross-modal representation learning approach for online handwriting recognition, leveraging image and time-series data to improve classification accuracy, convergence speed, and generalizability.

Contribution

It adapts triplet loss with a dynamic margin for cross-modal learning between images and time-series data, enhancing handwriting recognition performance.

Findings

Improved classification accuracy in handwriting recognition tasks.

Faster convergence and better generalization observed.

Enhanced adaptability between writers for online handwriting recognition.

Abstract

Cross-modal representation learning learns a shared embedding between two or more modalities to improve performance in a given task compared to using only one of the modalities. Cross-modal representation learning from different data types -- such as images and time-series data (e.g., audio or text data) -- requires a deep metric learning loss that minimizes the distance between the modality embeddings. In this paper, we propose to use the contrastive or triplet loss, which uses positive and negative identities to create sample pairs with different labels, for cross-modal representation learning between image and time-series modalities (CMR-IS). By adapting the triplet loss for cross-modal representation learning, higher accuracy in the main (time-series classification) task can be achieved by exploiting additional information of the auxiliary (image classification) task. We present a triplet loss with a dynamic margin for single label and sequence-to-sequence classification tasks. We perform extensive evaluations on synthetic image and time-series data, and on data for offline handwriting recognition (HWR) and on online HWR from sensor-enhanced pens for classifying written words. Our experiments show an improved classification accuracy, faster convergence, and better generalizability due to an improved cross-modal representation. Furthermore, the more suitable generalizability leads to a better adaptability between writers for online HWR.