Editing PAL Video Signal

[g_shyam1682]

Hello friends

i design a cross bar Project

In which, i have edit PAL Video signal and make one horizontal and one vertical black line on CCTV Monitor

My hardware is
--PIC 18F4431, 20MHz Crystal
--LM1881

My Horizontal line is OK

But my vertical line is fluctuated,
i use polling programming to detect horizontal sync;

what is batter, Polling Programming or Interrupt programming to detect horizontal sync?

what is problem with my Vertical line?

Please Help me to find out my problem

 

[keith1200rs]

You need to be using interrupts. Even so, I am not sure you will get a very stable vertical line using a microcontroller.

Keith

 

[IanP]

If you do it properly with interrupts I can’t see any reason why it shouldn’t be stable ..
Here is an example of video super-imposer based on a PIC and without external sync-separator:
https://www.micro-examples.com/public/microex-navig/doc/081-pic-osd-superimposer.html
But adding specialised IC such as the LM1881, as you plan, can only improve the operation of the whole circuit ..

IanP

 

[keith1200rs]

If you do it properly with interrupts I can’t see any reason why it shouldn’t be stable ..

It depends on your definition of stable. Interrupts have latency, which will vary depending on the exact timing of the interrupt relative to what the processor is doing at the time. The processor clock phase will vary within the line. If al these add up the less than the thickness of the vertical line you are generating then it might be good enough. For applications I have worked on I have generated a pixel clock phase locked to the line and driven the video with hardware (FPGA) so the image is rock solid.

Keith.

 

[g_shyam1682]

Hello friends

i design a cross bar Project

In which, i have edit PAL Video signal and make one horizontal and one vertical black line on CCTV Monitor

My hardware is
--PIC 18F4431, 20MHz Crystal
--LM1881

My Horizontal line is OK

But my vertical line is fluctuated,

I have used one 64uS Timer to edit Vertical line

it is work batter for one frame
but in next frame, position of vertical line is change

please, give me some hint or

some example code.

IN my project, PIC 18F4431 must be there.

 

[barrybear]

In Pal tv signals the second field is interlaced and starts its progress scanning from the centre top of the screen not from the top left as the first field started.

 

[g_shyam1682]

Thank barrybear

In Pal tv signals the second field is interlaced and starts its progress scanning from the centre top of the screen not from the top left as the first field started.

Can you give me some Example "C" language code.

My Micro is PIC18F4431