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How can I detect VSYNC through code?

Question asked by Mike Janzen on Mar 9, 2015
Latest reply on Mar 16, 2015 by igorpadykov

We are doing video display output from multiple video sources concurrently with Yocto 1.7, Linux 3.10.17, gstreamer 1.2.3, and gstreamer_imx directly to the Linux framebuffer (without X11) on a iMX6 dual processor (GPU is Vivante).

We've noticed video tearing, and want to eliminate that tearing.  The video tearing is illustrated here: Screen tearing - Wikipedia, the free encyclopedia.

We suspect the video tearing is due to performing OpenGL operations (swapping a buffer to the screen) when the HDMI vsync occurs.

 

Are there any alternate theories as to why the tearing occurs?

How can I write code that detects when this vsync occurs (polling is fine if that's the only way)?

 

Thanks,

 

Mike Janzen

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