What is VSYNC in android

Question

This explains VSYNC, but the pace is very fast, and i am unable to find any other good resource to understand this topic.

What i have understand is this;

VSYNC happens at every 16ms, and all of the frame components INPUT ANIMATION LAYOUT RECORD DRAW & RENDER only happens 1 in this time, so with VSYNC the frame rendering is synchronized, and it restricts frame from redrawing in the specified time.

Kindly guide me if this understanding is correct or not.

Answer 1

VSYNC is vertical sync. Its a term common to TVs, monitors, displays, etc. You can basically think of it as the refresh rate, its how often the display is actually refreshed. The display can only update on the VSYNC signal, so changes to the display are basically batched until the next VSYNC.

The term comes from old school TVs where the VSYNC would actually change 1 row at a time from top to bottom of the TV. That's why on some old tube TVs you could see a bar of change moving down the screen.

Answer 2

VSYNC is synchronization signal. It synchronize the display pipeline. Display pipeline contains the apps rendering & extra attributes to present image on display.

This VSYNC synchronization signal triggers based on FPS(Frames Per Second) configured for display. Assume the display is configured for 60fps i.e. 60 times display will be refreshed with new frames per second. So VSYNC signal will trigger after every 16.66ms (1/60 s).