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Visitor cemp
Registered: ‎10-15-2015

First 2 frames skipped: VDMA+VTC Generator+Axi4StreamToVidOut



My design consists of a VDMA, Video Timing Controller as generator and a Axi4Stream to Video Out block. Everthing works fine (hsync/vsync timings, data) but the first two frames of the VDMA frame buffer are skipped. The third frame is correctly transmitted. The locked signal of the Axi4StreamToVidOut block is high about one frame before the transmitted third frame. Running the VDMA in circular mode the first two frames are then always correctly transmitted.


I use the recommed settings for this setup from this topic Axi4s-to-video-out-can-t-lock-XAPP792


I found similar problems about this topic but nothing about this issue. I read that the VTC in detector mode needs about two frames for synchronization. Is that the same for VTC in generator mode? It is strange because the VTC knows hsync/vsync in advance.



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Xilinx Employee
Xilinx Employee
Registered: ‎08-02-2011

Re: First 2 frames skipped: VDMA+VTC Generator+Axi4StreamToVidOut

I'm not sure I understand where these frames are getting skipped. Are you saying the VDMA isn't transmitting them? Or that they aren't getting through the AXIS to Video Out?

The generator will start generating frames as soon as you enable it (unless of course, it's set up to use the detector too). The AXIS to Video core needs to line up SOFs on both interfaces to achieve lock so this may take a frame or two.
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