Towards Guidelines for Subjective Haptic Quality Assessment: A Case Study on Quality Assessment of Compressed Haptic Signals

Modern systems are multimodal (e.g., video, audio, smell), and haptic feedback provides the user with additional entertainment and sensory immersion. Standard recommendation groups extensively studied and focused on video and audio subjective quality assessment, especially in signal transmission. In that context, subjective quality assessment and Quality of Experience (QoE) of Haptic signals is at its infant age. We propose further analyzing the collected data from a recent subjective quality assessment campaign as part of the MPEG haptic standardization group. In particular, we are addressing the following questions: 1) How the emerging field of haptic signal QoE can benefit from existing efforts of video and audio quality assessment standards? 2) How to detect possible outliers or characterize the rater’s reliability? 3) How does the discriminability of haptic tests increases with the number of raters? Towards this goal, we question if traditional analysis as proposed for audio or video signal are suitable, as well as other state-of-the-art techniques. We also compare the discriminability of the haptics quality assessment tests with other modalities such as audio, video, and immersive content (360° contents). We propose recommendations on the number of raters required to meet the usual discriminability obtained for other perceptual modalities and how to process ratings to remove possible noise and biases. These results could feed future recommendations in standards such as BT500-14 or P.913 but for haptic signals.

1. INTRODUCTION

While visual and audio Quality of Experiences (QoE) has been investigated thanks to decades of product development and consumer adoption at scale, other senses, such as smell and touch (haptic), are still at an infant age. Nevertheless, the rise of new use cases such as Metaverse offers unique opportunities for technologies that enhance the user experience by stimulating all senses and could boost their development. In particular, the future of a more immersive experience could come with the possibility of transmitting haptic feedback. There are different types of haptic feedback. Vibrotactile haptics, this technology is already used in game controllers, keyboards of our smartphones, or VR controllers where tiny motors create vibrations. Microfluidics haptics where liquid or air is compressed into smart-textile [1]. Ultrasonic mid-air haptics¹ where multiple ultrasound loudspeakers generate waves adding up into a focal point and feel like a "virtual touch" by users. Surface haptics [2] where the friction between a user’s finger and a touchscreen is manipulated to create a tactile effect. Force control haptics [3] with levers, or other mechanical devices are used to exert force on a user’s hands, limbs, or whole body.