Subtle periodic signals, such as blood volume pulse and respiration, can be
extracted from RGB video, enabling noncontact health monitoring at low cost.
Advancements in remote pulse estimation -- or remote photoplethysmography
(rPPG) -- are currently driven by deep learning solutions. However, modern
approaches are trained and evaluated on benchmark datasets with ground truth
from contact-PPG sensors. We present the first non-contrastive unsupervised
learning framework for signal regression to mitigate the need for labelled
video data. With minimal assumptions of periodicity and finite bandwidth, our
approach discovers the blood volume pulse directly from unlabelled videos. We
find that encouraging sparse power spectra within normal physiological
bandlimits and variance over batches of power spectra is sufficient for
learning visual features of periodic signals. We perform the first experiments
utilizing unlabelled video data not specifically created for rPPG to train
robust pulse rate estimators. Given the limited inductive biases, we
successfully applied the same approach to camera-based respiration by changing
the bandlimits of the target signal. This shows that the approach is general
enough for unsupervised learning of bandlimited quasi-periodic signals from
different domains. Furthermore, we show that the framework is effective for
finetuning models on unlabelled video from a single subject, allowing for
personalized and adaptive signal regressors.

提出了一种新的非对抗无监督学习框架，用于从未标记的视频数据中直接提取血容量脉搏，以实现低成本的非接触健康监测，并展示了该框架在调整模型和个性化适应信号回归方面的效果。

SiNC+: 自适应基于相机的生命体征测量及周期信号无监督学习

SiNC+: Adaptive Camera-Based Vitals with Unsupervised Learning of  Periodic Signals

This paper presents a neural vocoder based on a denoising diffusion
probabilistic model (DDPM) incorporating explicit periodic signals as auxiliary
conditioning signals. Recently, DDPM-based neural vocoders have gained
prominence as non-autoregressive models that can generate high-quality
waveforms. The neural vocoders based on DDPM have the advantage of training
with a simple time-domain loss. In practical applications, such as singing
voice synthesis, there is a demand for neural vocoders to generate
high-fidelity speech waveforms with flexible pitch control. However,
conventional DDPM-based neural vocoders struggle to generate speech waveforms
under such conditions. Our proposed model aims to accurately capture the
periodic structure of speech waveforms by incorporating explicit periodic
signals. Experimental results show that our model improves sound quality and
provides better pitch control than conventional DDPM-based neural vocoders.

基于去噪扩散概率模型（DDPM）的神经声码器在辅助条件信号中引入显式周期信号，以准确捕捉语音波形的周期结构，改善音质和提供更好的音高控制。