# Introduction

**360-degree video** is a form of moving image sequence that surrounds the viewer in virtual space. When wearing an [HMD](https://pimkb.gitbook.io/pimkb/preserving-xr-hardware/head-mounted-display#head-mounted-displays), the viewer is able to freely rotate their head, determining their viewing direction. This can be contrasted with traditional, fixed-perspective video in which the viewing angle is fixed.

As the video content is linear, the viewing position is either fixed or follows a pre-determined path ("on rails") captured in the video. However, a degree of positional interactivity can be introduced through hotspots or portals which, when interacted with in the virtual scene, jump the viewer to another piece of 360-degree video content. Adding these requires the use of a software layer in addition to the video, which places the content somehwere between 360-degree video and [3D software](https://pimkb.gitbook.io/pimkb/preserving-3d-software).

360-degree video can be created in a number of different ways:

* Captured by a **camera** or array of camera lenses;
* Generated as an export from **3D rendering software** (e.g. Blender);
* Generated from a **real-time 3D** [**game engine**](https://pimkb.gitbook.io/pimkb/preserving-3d-software/game-engines#list-of-engines) (either as a standalone experience or as documentation of a real-time 3D VR experience).

It is then played back using video playback software that supports 360° video and viewed via [XR hardware](https://pimkb.gitbook.io/pimkb/preserving-xr-hardware/head-mounted-display). 

## Assessing 360-degree Video

* How was the 360-degree video **created**? 
  * Was it created through **camera capture**? 
    * If so, is the camera model and captured video format known?
  * Was it created using a **3D software tool** e.g. 3D renderer or game engine? 
    * Is the capture and output format of the video known? 
  * Did the video undergo a **stitching** process
    * Is the software used for stitching known? 
  * Was the video **edited**? 
    * If so, what software was used? 
    * Are these production assets available? 
* By inspecting file **metadata**, are you able to determine key characteristics of the 360-degree video format? If not you will need to determine these manually. See [Video Formats](https://pimkb.gitbook.io/pimkb/preserving-360-video/video-formats) for more information about these.
  * The [projection format](https://pimkb.gitbook.io/pimkb/video-formats#projection-format) used e.g. cubemap, equirectangular. 
  * Whether the video is [monoscopic or stereoscopic](https://pimkb.gitbook.io/pimkb/video-formats#monoscopic-vs-stereoscopic).
  * The [codec and pixel format](https://pimkb.gitbook.io/pimkb/video-formats#video-file-format) that the video has been encoded with.
* What kind of **audio format** does the video use? 
  * If this uses [spatial audio](https://pimkb.gitbook.io/pimkb/preserving-360-video/spatial-audio), how was this created? 
  * How has the spatial audio been encoded in the video file?