`timescale 1ns / 1ps
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// Company: 
// Engineer: 
// 
// Create Date:    10:30:24 12/03/2013 
// Design Name: 
// Module Name:    butterfly 
// Project Name: 
// Target Devices: 
// Tool versions: 
// Description: 
//
// Dependencies: 
//
// Revision: 
// Revision 0.01 - File Created
// Additional Comments: 
//
//////////////////////////////////////////////////////////////////////////////////
module butterfly (
    D0,D1,D2,D3,//蝶形运算输入
    F0,F1,F2,F3,//结果输出
    DCT_or_HDT//DCT变换还是Hadaman变换（0--DCT，1--HDT）
    );
    parameter Level_Length = 16;
	input [Level_Length-1:0] D0,D1,D2,D3;
	input DCT_or_HDT;
	output [Level_Length-1:0] F0,F1,F2,F3;
	
	wire [Level_Length-1:0] T0,T1,T2,T3;
	wire [Level_Length-1:0] D1_scale,D3_scale;
	
	assign D1_scale = (DCT_or_HDT == 1'b1)? D1:{D1[Level_Length-1],D1[Level_Length-1:1]};
	assign D3_scale = (DCT_or_HDT == 1'b1)? D3:{D3[Level_Length-1],D3[Level_Length-1:1]};
	
	assign T0 = D0 + D2;
	assign T1 = D0 - D2;
	assign T2 = D1_scale - D3;
	assign T3 = D1 + D3_scale;
	
	assign F0 = (T0 + T3);
	assign F1 = (T1 + T2);
	assign F2 = (T1 - T2);
	assign F3 = (T0 - T3);
endmodule