Quality switcher

[ferferga]

Originally in jellyfin/jellyfin-web#1993 (specific comment)

I want to give the concept I had in mind for making the quality switcher great:

• First of all, quality options shouldn't be handled by clients. According to the file's bitrate, server should generate a combination of possible options and return them to client. This is good for consistency, as users will have same quality options in web and in Android.

With the current system, a 1080p - 30 Mbps option appears when I'm watching a 15 Mbps movie, which doesn't make any sense.

• We should only have two "default" options that will appear all the times:

  * **Maximum**: Stream original file when device is capable of direct play or the maximum quality transcoded version that the device can handle (in case it's not compatible)
  
  * **Auto**: Stream's quality changes in real time based on the connectivity of the client.
  

• Keep only resolution options and remove any mention to bitrates. They're confusing for most people. We can add in the nerd stats of each player an option for requesting specific bitrates in case we really want to keep this. In that case, client should know from server (as mentioned above) the bitrate of the original file, so user can't request a file with a bitrate higher than the original one.

• Add an option in each's client settings (Data saver mode for instance) where the bitrates (except in Maximum) of each of the resolutions are cut in half or by a quarter. So, for instance, if for a movie in 4K@50Mbps server determines that best bitrate for 720p is 4 Mbps, client forces the server to use 2 Mbps instead.

TLDR, the idea is to make the quality switcher simpler and common, like the one found in YouTube, Vimeo, etc... While still being useful for power users and the use case of a media server.

I guess this will need to wait for 11.0 once we have an stable API, but would be great to have as much input as possible for this.