360 video projection
A 360 video projection is any of many ways to map a spherical field of view to a flat image. It is used to encode and deliver the effect of a spherical, 360-degree image to viewers such as needed for 360-degree videos and for virtual reality. A 360 video projection is a specialized form of a map projection, with characteristics tuned for the efficient representation, transmission, and display of 360° fields of view.
See Cube mapping.
Equi-Angular Cubemap (EAC)
The Equi-Angular Cubemap (EAC) projection was detailed by Google on March 14, 2017. In January 2018 the company started using the spherical projection to stream 360 degree videos on YouTube. The main goal of the EAC projection is to distribute pixels as evenly as possible across the sphere so that the density of information is consistent, regardless of which direction the viewer is looking.
The Pyramid projection was detailed by Facebook on January 21, 2016, mainly aimed at VR video. The video is rendered in multiple viewports (in Facebook's case 30) where the base of the pyramid contains the full resolution and is right in front of the viewer, while the sides are rendered with a gradually decreasing resolution. The company claims an 80% reduction in bandwidth with this projection, with the disadvantage that many more viewports need to be rendered and stored.
- "Bringing pixels front and center in VR video". Google. 2017-03-14. Retrieved 2018-04-02.
- "Improving VR videos". YouTube Engineering and Developers Blog. Retrieved 2018-04-02.
- "[YouTube] 3D/2D 360° videos - now encoded in a new, proprietary & non-standard format · Issue #15267 · rg3/youtube-dl". GitHub. Retrieved 2018-04-02.
- "Next-generation video encoding techniques for 360 video and VR". Facebook Code. Retrieved 2018-04-02.