YouTube uses a countdown to display when a premiere starts. By looking through the minified client side studio source code, we can find the original video ID used internally for the countdown.
In fact, there are actually multiple countdown videos, because in the future, creators will be able to customize their premieres with trailers and countdown themes.
Premiere classic VIDEO_PREMIERE_INTRO_THEME_DEFAULT
Bright VIDEO_PREMIERE_INTRO_THEME_INSPIRATIONAL
Inspirational VIDEO_PREMIERE_INTRO_THEME_CALM
Dramatic VIDEO_PREMIERE_INTRO_THEME_ENTERTAINMENT
Happy VIDEO_PREMIERE_INTRO_THEME_PLAYFUL
Sci-fi VIDEO_PREMIERE_INTRO_THEME_GRUNGE
Ambient VIDEO_PREMIERE_INTRO_THEME_NATURE
Gentle VIDEO_PREMIERE_INTRO_THEME_TACTILE
Contemporary VIDEO_PREMIERE_INTRO_THEME_CONTEMPORARY
Cinematic VIDEO_PREMIERE_INTRO_THEME_TECHNICAL
Alternative VIDEO_PREMIERE_INTRO_THEME_MUSIC
