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Hitoshi Imaoka

5 accepted papers

2025

Learning the Optimal Stopping for Early Classification within Finite Horizons via Sequential Probability Ratio Test

ICLR 2025poster

Time-sensitive machine learning benefits from Sequential Probability Ratio Test (SPRT), which provides an optimal stopping time for early classification of time series. However, in *finite horizon* scenarios, where input lengths are finite, determining the optimal stopping rule becomes computational…

2023

Blood Oxygen Saturation Estimation from Facial Video Via DC and AC Components of Spatio-Temporal Map

ICASSP 2023accepted

Peripheral blood oxygen saturation (SpO2), an indicator of oxygen levels in the blood, is one of the most important physiological parameters. Although SpO2 is usually measured using a pulse oximeter, non-contact SpO2 estimation methods from facial or hand videos have been attracting attention in rec…

Cited by 0SourceScholar
2023

Toward Asymptotic Optimality: Sequential Unsupervised Regression of Density Ratio for Early Classification

ICASSP 2023accepted

Theoretically-inspired sequential density ratio estimation (SDRE) algorithms are proposed for the early classification of time series. Conventional SDRE algorithms can fail to estimate DRs precisely due to the internal overnormalization problem, which prevents the DR-based sequential algorithm, Sequ…

Cited by 0SourceScholar
2022

Heart Rate and Oxygen Saturation Estimation from Facial Video with Multimodal Physiological Data Generation

ICASSP 2022accepted

Efforts to estimate multiple physiological parameters such as heart rate and oxygen saturation from facial videos have been made. However, training robust machine learning models for the estimation is challenging without large multimodal physiological datasets containing multiple physiological param…

Cited by 0SourceScholar
2021

Sequential Density Ratio Estimation for Simultaneous Optimization of Speed and Accuracy

ICLR 2021spotlight

Classifying sequential data as early and as accurately as possible is a challenging yet critical problem, especially when a sampling cost is high. One algorithm that achieves this goal is the sequential probability ratio test (SPRT), which is known as Bayes-optimal: it can keep the expected number o…