**Abstract**

New real-world capture and rendering systems are flooding the market. Mobile phones are now equipped with more than one camera, thus creating multi-view portable systems. Virtual reality rendering equipment is now within the reach of the consumer and many applications are available to the user. A big effort is being made by industrial and research bodies for spreading the new technologies. In this contribution, an overview of the main issues related to the quality evaluation of immersive media is presented.

**Keywords:** virtual reality, immersive media, quality of experience, multiple views, computer-generated data

### **1. Introduction**

Recent years have witnessed an overwhelming rise in multimedia technologies. Their impact on the consumer is very high. The terms immersivity, virtual reality, augmented reality, and 3D content have now become familiar even to nonprofessionals. Under the boost of the entertainment sector and, more generally, of multimedia interaction, many novel services have been proposed. Immersive media can be defined as technologies that attempt to produce or imitate the physical world by exploiting computer-generated data. This status is achieved by techniques, both aural and visual, able to completely engage the user [1]. As stated by Dale Lovell in [2], "engagement is great, but immersion is the future. Immersion is when you forget the message entirely, forget you are the audience even, and instead fall into a newly manufactured reality".

One of the first approaches in the direction of providing the user with the feeling of immersion was the Sensorama system in 1957. It is a mechanical device, which includes a stereo color display, fans to generate the sensation of the wind, odor emitters, a stereo sound system, and a chair mounted on a moving platform. The experience shown to users consisted of a motorcycle tour through the streets of New York. The user, sitting on the chair, was able to relive the riding experience through sounds, chair movements and pre-recorded images. The smell of the city (gasoline vapors and snack bar pizza) has been recreated by chemicals. According to the situation surrounding the user, different effects are rendered (i.e., when the rider approaches a bus, the typical bus noise and gasoline smell are sent to the user). However, the user interaction was quite limited.

Nowadays different devices are available for acquiring, processing, and rendering information in the best interactive way. They are the basic elements of immersive media, such as virtual reality, augmented reality, and mixed reality.

*Virtual Reality* replaces the user's physical environment (including surrounding sound) with a computer generated, interactive, 3D environment in which a person is immersed. One of the identifying marks of a virtual reality system is the use of head-mounted displays worn by users. These displays block out all the external world and present to the wearer a view that is under the complete control of the computer. This allows a scene to be seen in any direction from one viewpoint. When using a head-mounted display to watch such content, the viewing direction can be changed by head movements. A less immersive effect can also be obtained by rendering virtual reality content with different devices. On smartphones and tablets, the viewing direction can be changed by touch interaction or by moving the device around, thanks to built-in sensors. On a desktop computer, the mouse or keyboard can be used for interacting with omnidirectional video.

*Augmented Reality* combines the real-world with computer-generated data. Most of the AR research is currently concerned with the use of video imagery which is digitally processed and augmented by adding computer-generated graphics. The goal is to enhance instead of recreating the real scenario. A commonly used example of augmented reality is the Snapchat photo filtering tool.

*Mixed Reality* fuses the information collected by the real world with ad-hoc created digital ones. In this case the user may interact seamless with both. The user is generally equipped with a semi-transparent head-mounted display or with smart glasses. In mixed reality, the user must still be aware that he or she is present in the "real world." There are three components needed to make an augmented-reality system work: 1) the see-through rendering system, 2) the tracking system, and 3) mobile computing power. All these components are fundamental, and their performances highly affect the perceived Quality of Experience (QoE).

Many sectors will benefit from these technologies. In the following, a few examples are reported.


To achieve immersive goals, sophisticated media acquisition devices, new rendering systems, compression techniques, have been designed and, consequently, new application areas. Among others, 360° camera, light field camera, multiview camera setup, virtual reality equipment (audio and video), AR equipment, Tactile tools.

Especially when human subjects are involved, the impact of new technology on the perceived experience is a fundamental issue. If the human-in-the-loop factor is not properly addressed, the novel technology may not be successful. The negative trend of stereo content, especially in a home environment, is probably because the actual 3D content production, delivery, and presentation, are not compliant with 3D QoE. The success of the immersive imaging market relies on the ability of 3D

*QoE and Immersive Media: A New Challenge DOI: http://dx.doi.org/10.5772/intechopen.99973*

systems to provide added value compared to conventional monoscopic imaging (i.e., depth feeling or parallax motion) coupled with high-quality image contents. Dealing with these issues can result in the creation of perceivable impairments in the 3D content that may be originated in different points of the 3D chain, from content creation to display techniques. Many artifacts are common to the 2D imaging systems. However, novel distortions typical of the 3D structure should be considered (i.e., crosstalk or keystone) especially because their presence highly impacts the perceived quality (i.e., compression artifacts due to coding). Subjects are prone to prefer 2D contents to 3D ones, as soon as fatigue and discomfort are induced during the content presentation. The understanding of the quality of the experience is mandatory. However, this task is quite challenging. In the following, a brief overview of quality and the related issues is reported.
