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/////////////////////////////////////////////////////////////////////

////                                                             ////

////  JPEG Entropy Coding, Huffman Encoding                      ////

////                                                             ////

////  Creates 8bit output stream from huffman codes.             ////

////  See accompanying testbench how to use this code.           ////

////                                                             ////

////  Author: Richard Herveille                                  ////

////          richard@asics.ws                                   ////

////          www.asics.ws                                       ////

////                                                             ////

/////////////////////////////////////////////////////////////////////

////                                                             ////

//// Copyright (C) 2001 Richard Herveille                        ////

////                    richard@asics.ws                         ////

////                                                             ////

//// This source file may be used and distributed without        ////

//// restriction provided that this copyright statement is not   ////

//// removed from the file and that any derivative work contains ////

//// the original copyright notice and the associated disclaimer.////

////                                                             ////

////     THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY     ////

//// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED   ////

//// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS   ////

//// FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR      ////

//// OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,         ////

//// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES    ////

//// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE   ////

//// GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR        ////

//// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF  ////

//// LIABILITY, WHETHER IN  CONTRACT, STRICT LIABILITY, OR TORT  ////

//// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT  ////

//// OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE         ////

//// POSSIBILITY OF SUCH DAMAGE.                                 ////

////                                                             ////

/////////////////////////////////////////////////////////////////////

//  CVS Log

//

//  $Id: huffman_enc.v,v 1.2 2002-10-31 12:50:40 rherveille Exp $

//

//  $Date: 2002-10-31 12:50:40 $

//  $Revision: 1.2 $

//  $Author: rherveille $

//  $Locker:  $

//  $State: Exp $

//

// synopsys translate_off

`include "timescale.v"

// synopsys translate_on

module huffman_enc(clk, rst, tablesel, di, die, do, doe, busy);

  input        clk;      // clock

  input        rst;      // asynchronous active low reset

  input  [1:0] tablesel; // huffman table select (0-3)

  input  [7:0] di;       // data-in

  input        die;      // data-in enable

  output [7:0] do;       // data out

  output       doe;      // data-out enable

  output       busy;     // busy. Do not assert die while busy asserted

  reg [7:0] do;

  reg       doe;

  wire [12:0] henc_dc_lum;

  wire [14:0] henc_dc_chr;

  wire [19:0] henc_ac_lum, henc_ac_chr;

  reg  [ 4:0] codelen;

  reg  [15:0] code;

  reg         ddie;

  reg         state;

  reg  [22:0] sreg;

  reg  [ 4:0] cnt;

  // include default tables

  `include "huffman_tables.v"

  //

  // hookup huffman tables

  //

  assign henc_dc_lum = jpeg_dc_luminance_huffman_enc( di[3:0] );

  assign henc_dc_chr = jpeg_dc_chrominance_huffman_enc( di[3:0] );

  assign henc_ac_lum = jpeg_ac_luminance_huffman_enc( di[7:4], di[3:0] );

  assign henc_ac_chr = jpeg_ac_chrominance_huffman_enc( di[7:4], di[3:0] );

  //

  // split table-data into codeword and codeword-length

  //

  always @(posedge clk)

    case (tablesel) // synopsys full_case parallel_case

      2'b00: // DC Luminance

        begin

            codelen <= #1 henc_dc_lum[12: 9] +4'h1;

            code    <= #1 henc_dc_lum[ 8: 0];

        end

      2'b01: // DC Chrominance

        begin

            codelen <= #1 henc_dc_chr[14:11] +4'h1;

            code    <= #1 henc_dc_chr[10: 0];

        end

      2'b10: // AC Luminance

        begin

            codelen <= #1 henc_ac_lum[19:16] +4'h1;

            code    <= #1 henc_ac_lum[15: 0];

        end

      2'b11: // AC Chrominance

        begin

            codelen <= #1 henc_ac_chr[19:16] +4'h1;

            code    <= #1 henc_ac_chr[15: 0];

        end

    endcase

  //

  // wait for encoder table(s)

  //

  always @(posedge clk)

    ddie <= #1 die;

  //

  // data out statemachine

  //

  always @(posedge clk or negedge rst)

    if(~rst)

      begin

          state <= #1 1'b0;

          cnt   <= #1 5'h0;

      end

    else

      case (state)

        1'b0:

         if(ddie)

           begin

               if( (cnt + codelen) > 7 )

                 state <= #1 1'b1;

               cnt <= #1 (cnt + codelen);

           end

        1'b1:

         begin

             if (ddie)

             begin

                 cnt <= #1 (cnt + codelen) - 5'h8;

                 if( (cnt + codelen) - 5'h8 < 8)

                   state <= #1 1'b0;

             end

             else

             begin

                if( (cnt -5'h8) < 8)

                  state <= #1 1'b0;

                cnt <= #1 (cnt -5'h8);

             end

         end

      endcase

  assign busy = state;

  always @(posedge clk)

    if(ddie)

      sreg <= #1 (sreg << codelen) | code;

  always @(posedge clk)

    doe <= #1 state;

  always @(posedge clk)

    do <= #1 sreg >> (cnt -5'h8);

endmodule