Problems with the CVI and CVO Sof-Signals

Hi,

I really need help. I have a simple VideoProcessing Modul. I hav a CVI --> ChromaResampler --> CVO, and a Cylone IV E

I have different clocks for the PixelClock-Input an the PixelClock Output. Both are 74.25MHz but the Input PixelClock is an external Clock, and the Output-Pixel_Clock is an PLL-generatet Pixel-Clock. I need this PLL - Clock because the other clock has Jitter/Wander on it.

I don't have a NIOS in my System. I connected the sof_input and the sof_input_locked Signal with the output_sof_locked and the outpu_sof-Signal.

I changed some lines in the control-vhdl-Code in the IP-File.

In this File "alt_vipcti120_Vid2IS_control" I changed

Line 143 assign enable = 1'b1;

Line 113 - 121

genlock_enable <= 1'b1;

interrupt_enable <= 2'b00;

enable_reg <= 1'b1;

status_update_int_reg <= 1'b0;

stable_int_reg <= 1'b0;

sof_sample <= 14'd2194;

sof_subsample <= 2'd1;

sof_line <= 13'd1124;

refclk_divider_value <= 14'd1;

On the CVO File "alt_vipitc120_IS2Vid_control"

I changed Line 94 - 99

if (rst) begin

genlock_enable_reg <= 2'b1;

interrupt_enable <= 2'b1;

enable_reg <= 1'b1;

status_update_int_reg <= 1'b0;

genlocked_int_reg <= 1'b0;

and Line 117

assign enable = 1'b1;

This works for about 3 Minutes, in this Time I can see a stable picture, but then I get an CVI-FIFO Overflow and my analyzer can still detect the right Videoformat, but I only get a black picture. After a few Minutes the picture startet to change the colour.

If I use my Video-Input_pixel-Clock as my VideoOutput_Pixel-Clock I alwys get a stable picture.

Please tell me, what can I do against this overflow? What can I do to synchonize the Input and the Output without the same Pixel_clock.

Can anybody help me?

Thanx Anja