If you change the quality of the video, another video is loaded into the players?

Question

Video broadcast

Good afternoon. Please tell me there is a site with films. For example, the popular gidonline, where you can choose the video quality (360, 480, 720, 1080). When you change the quality - the video file itself changes or not. Or how does it happen that one video has different qualities for switching?

Answer 1

A video is several streams: the video itself, to which others can be added: audio tracks, subtitles...
A video stream is a set of frames. The display is handled by a program called a renderer. How many lines you order for her, so much she will display from the frame. (most likely, the number of columns will also change proportionally).

Answer 2

When you load the player, you get a playlist - a list of all possible qualities for a given video. In 99% of cases, these are separate files of the appropriate resolution. If you change the resolution, the player accesses the new file while maintaining the viewing position.