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5986 Discussions

Clocked Video Output Settings

Altera_Forum
Honored Contributor II
1,278 Views

Dear all, 

 

I'm using the Test Pattern Generator (from Altera) to feed the clocked video output. I configured it to generate a 176x144(QCIF) pixels progressive colorbar for my DVI output.  

The colorspace is RGB with 8 bits per color space using 4:4:4 sampling. 

The clocked video output is configured like this: 

Image Width: 176 pixels 

Image Height: 144 lines 

Bits per pixel per color plane: 8 

Color plane transmission format: parallel 

Pixel fifo size: 176 pixels 

Sync signals: on separate wires 

 

But how to set these synchronization settings like h/v sync, h/v front porch, h/v back porch? Altera has some default settings for HD1080p, bu can anybody tell me know to calculate these parameters for other resolutions? 

 

Thanks!
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4 Replies
Altera_Forum
Honored Contributor II
130 Views

Hi, 

I use the following link: 

http://tinyvga.com/vga-timing (http://tinyvga.com/vga-timing

For VGA resolutions, but it is not for small resolutions like QSIF. 

 

BR,
Altera_Forum
Honored Contributor II
130 Views

DVI is not usually used for such low resolutions. The DVI spec has a minimum pixel clock of 25.175 MHz. To achieve this clock rate with such a low resolution would require a high refresh rate or unusually large blanking intervals. 

 

The HDMI spec has a similar minimum clock frequency. For resolutions like 720x480i60, the HDMI spec requires pixel repetition to get the clock rate high enough. 

 

What are you trying to feed with your DVI output? 

 

Perhaps you need to consider scaling up your video to something like 640x480p60.
Altera_Forum
Honored Contributor II
130 Views

Thanks you two. The output from DVI is connected with a 23 inches LCD monitor. My plan is to test the smaller resolution first, then gradually scale up to larger resolution like VGA or HD1080

Altera_Forum
Honored Contributor II
130 Views

I would start with 640x480. I haven't tried before so I don't know for sure, but I suspect most DVI monitors will not work with a resolution much lower than this.

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