always @(posedge clk_54, posedge reset) begin
if (reset)
    cntr <= 0;
else if (flag_in)
    cntr <= cntr+1;
end

always @(posedge clk_54, posedge reset) begin
if (reset) begin
    Y  <= 0;
    Cb <= 0;
    Cr <= 0; end
if (cntr==0)
    Cb <= YCbCr;
else if ((cntr==1)||(cntr==3))
    Y <= YCbCr;
else if (cntr==2)
    Cr <= YCbCr;
end