2.9.2. Using VSYNC

To use VSYNC, optimize your application for the highest possible frame rate. The aim is to have the application frame rate significantly higher than the screen display rate.

For example, assume your application produces frames at 40 Frames Per Second (FPS) and the screen display rate is 30 FPS. Figure 2.1 shows that 4 frames are generated for every 3 screen display updates.

Figure 2.1. Screen updates and frame completes

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Activating VSYNC locks the application frame rate to 30 FPS. The application generates a frame then stops generating any new graphics until after the frame is displayed. When the frame is displayed on screen the application starts the next frame. This process is shown in Figure 2.2. Power is saved because the GPU is not active between the end of frame generation and the screen display update.

Figure 2.2. Screen updates and frame completes with VSYNC

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