--/*************************************************************************
--  
-- Filename: YCbCr_RGB_conv.vhd
-- 
-- Author: Rejean Lau, Maziyar Khorasani, Yongie Liu, Ram Swamy
   
    
-- Description: This is the YCbCr to RGB converter model which implements
--              the conversion formulas for 8 bit Y,Cb,Cr inputs


--			R = 1.164(Y' - 16) + 1.596(Cr - 128)
--			G = 1.164(Y' - 16) - (0.813)(Cr - 128) - 0.392(Cb - 128)
--			B = 1.165(Y' - 16) + 2.017(Cb - 128)


-- ***************************************************************************/

library IEEE; 
use IEEE.std_logic_1164.all;
use IEEE.std_logic_arith.all;
--use IEEE.std_logic_unsigned.all;
use IEEE.std_logic_signed.all;
use IEEE.Numeric_STD.all;
--library virtex; 
--use virtex.components.all; 
--library synplify; 
--use synplify.attributes.all; 


entity ycrcb2rgb is
  port (Y,Cr,Cb : in std_logic_vector(7 downto 0); 
        clk,rst : in std_logic;
          R,G,B : out std_logic_vector(7 downto 0));
 end ycrcb2rgb;


architecture logic of ycrcb2rgb is

signal Y_reg,CR_reg,CB_reg: std_logic_vector(7 downto 0);

signal X_int,A_int,B1_int,B2_int,C_int: std_logic_vector(19 downto 0);
signal Y_int1,CR_int1,CB_int1: std_logic_vector (8 downto 0);
signal R_int,G_int,B_int: std_logic_vector(19 downto 0);


begin
 P1:process (clk,rst)
  begin
   if (rst = '1') then
      Y_reg <= "00000000"; CR_reg <= "00000000";CB_reg <= "00000000";
   elsif (rising_edge (clk)) then
      Y_reg <= Y; CR_reg <= Cr;CB_reg <= Cb;
   end if;


end process P1;

Y_int1 <= (('0' & Y_reg) - "000010000"); 		--16 for 8 bit
CR_int1 <= (('0' & CR_reg) - "010000000");	 	--128 for 8 bit
CB_int1 <= (('0' & CB_reg) - "010000000");		--128 for 8 bit



P2:process (clk,rst)
  begin
   if (rst = '1') then
      X_int <= (others => '0'); 
      A_int <= (others => '0'); 
      B1_int <= (others => '0'); 
      B2_int <= (others => '0');
      C_int <= (others => '0');
   elsif  (rising_edge (clk)) then
      X_int  <= ("00100101010" * (Y_int1));--(Y_reg - "10000"));-- Y_reg - 16
      A_int  <= ("00110011000" * ( CR_int1));--(CR_reg - "10000000"));  -- Cr_reg - 128
      B1_int <= ("00011010000" * ( CR_int1));--(CR_reg - "10000000")); 
      B2_int <= ("00001100100" * (CB_int1));--(CB_reg - "10000000")); -- Cb_reg - 128
      C_int  <= ("01000000100" * (CB_int1));--(CB_reg - "10000000")); 
   end if;
end process P2;


P3:process (clk,rst)
  begin
   if (rst = '1') then
      R_int <= (others => '0'); 
      G_int <= (others => '0'); 
      B_int <= (others => '0'); 
   elsif  (rising_edge (clk)) then
      R_int <= X_int + A_int;
      G_int <= X_int - B1_int - B2_int;  
      B_int <= X_int + C_int; 
   end if;
end process P3;

P4:process (R_int)
   begin
      if (R_int(19) = '1') then
          R <= "00000000";
      elsif (R_int(18 downto 16) = "000") then
          R <= R_int(15 downto 8);
      elsif (R_int(16) = '1') then
          R <= "11111111";
      end if;
end process P4;

P5:process (G_int)
   begin
      if (G_int(19) = '1') then
          G <= "00000000";
      elsif (G_int(18 downto 16) = "000") then
          G <= G_int(15 downto 8);
      elsif (G_int(16) = '1') then
          G <= "11111111";
      end if;
end process P5;

P6:process (B_int)
   begin
      if (B_int(19) = '1') then
          B <= "00000000";
      elsif (B_int(18 downto 16) = "000") then
          B <= B_int(15 downto 8);
      elsif (B_int(16) = '1') then
          B <= "11111111";
      end if;
end process P6;


end logic ;