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Facts and Analysis of Virtual Reality


2015-8-18 mLAB

Virtual Reality (VR) glasses are the hottest products in the VR field. Through the use of VIR Glass and Samsung Gear VR Glass, Huawei mLAB has conducted an in-depth analysis on future network requirements. The analysis is based on basic VR principles, key technologies, the capabilities of the mainstream devices, and content source characteristics.

The analysis conclusions are as follows:

1. 360-degree (panoramic) video. When shooting a video, the user places the camera in the center position and records images in all directions. When watching a 360-degree video on the phone, the user scrolls the screen (or invokes the embedded gyroscope) to switch the view angle. To watch a 360-degree YouTube video on the PC, use the mouse to drag the view.

A VR experience is enabled by wearing a pair of VR glasses and watching a 360-degree video. When the wearers turn around, the viewing angle changes accordingly. They can also have a walk-around experience by staring at a set point.

A multi-angle video is produced by shooting the same object from different angles by using multiple cameras. Multi-angle videos are available on YouTube (but not yet available on the mobile phone app). To switch the view angle, the user clicks any of the four camera icons on the right side of the video play window. Images from each angle are shot by an independent camera.

2. Based on the 360-degree panoramic view, a VR video forms a reality view by aggregating multiple panoramic images. The core features of VR videos are interactivity and the sense of immersion from active visual angle creation. Currently, a 360-degree panoramic experience and simple interaction are mainly involved in VR.

3. Principles of panoramic video integration: Images are concurrently shot from different view angles using six cameras (depending on the view size). Frames of the six videos are integrated to form panoramic images along the timeline.

4. VR principles: Views are virtually imaged by using lenses. For example, the lenses are 2 or 3cm in front of the camera, while the screen is 3 to 6 cm away from the lenses. The virtual images will be presented as they are 25 to 30 cm in front of the user’s eyes. By wearing a pair of VR glasses, a user will see left-screen and right-screen images displayed on the phone screen and acquire the immerse experience after the brain processes the left-eye and right-eye virtual images.

VR glasses with a built-in screen and VR glasses applicable to mobile phones are both available.

5. When watching a 2D 360-degree panoramic video on a mobile phone, the user will see one image on the phone screen. By wearing a pair of VR glasses, the user will see an image that is the same as that seen by the naked eye.

When watching a 3D 360-degree panoramic video on a mobile phone, the user will see two panoramic images, each of which is shot by six cameras. By wearing a pair of VR glasses, the user will see an image that is larger than that seen by the naked eye.

6. A 2D 360-degree video is shot using six cameras. Currently, videos on the VR APP are mostly 2D 360-degree videos. A 3D 360-degree video is shot using 12 cameras. Users will see images with different angles and depths at the same time so as to achieve the 3D effect.

The following table lists the resolution information about 2D and 3D 360-degree panoramic videos (with the 4K resolution) based on Gear VR (with the FOV being 96 degrees).

7. The following table lists the characteristics of source videos from 360Heros . 3D 360-degree videos usually adopt a higher coding algorithm. The code rate of 3D 360-degree videos increases, as compared to 2D 360-degree videos with the same resolution.

8. Gear VR (with the FOV being 96 degrees) stimulates an experience where a user watches a 1749-inch screen from 20m way. The entry-level retinal PPI requirement is 4.366. The video resolution for each eye is 1108 x 1247 (equaling 3840x2160/6). The actual watching PPI is 0.954, which is 21.9% of the entry-level retinal PPI requirement. The definition experience is similar to watching a 240p video on a 6-inch screen.

9. The following table lists the expected resolution and bandwidth requirements of true 3D panoramic videos in the future. The results are based on the human visual PPI calculation theory.

3D videos played in theaters have far lower requirements on resolution and bandwidth than true 3D panoramic videos. This is because only the screen images of 3D videos played in theaters are displayed as 3D. All the other views (left, right, rear, upper, and lower) are simply panoramic pictures.

10. Current status: Normal 4K VR videos with low code rates will be the first to enter the consumer market. For example, the available videos on the Oculus platform have a maximum resolution of 4K and peak code rate of 20Mbps. With the video coding/decoding capabilities being restricted, it will take some time for the real VR video era to arrive.