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//// ////
//// JPEG Encoder Unit ////
//// ////
//// Author: Richard Herveille ////
//// richard@asics.ws ////
//// www.asics.ws ////
//// ////
/////////////////////////////////////////////////////////////////////
//// ////
//// Copyright (C) 2002 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: jpeg_encoder.v,v 1.3 2002-10-31 12:51:44 rherveille Exp $
//
// $Date: 2002-10-31 12:51:44 $
// $Revision: 1.3 $
// $Author: rherveille $
// $Locker: $
// $State: Exp $
//
// Change History:
// $Log: not supported by cvs2svn $
// Revision 1.2 2002/10/23 18:58:51 rherveille
// Fixed a bug in the zero-run (run-length-coder)
//
// Revision 1.1 2002/10/23 09:07:01 rherveille
// Improved many files.
// Fixed some bugs in Run-Length-Encoder.
// Removed dependency on ud_cnt and ro_cnt.
// Started (Motion)JPEG hardware encoder project.
//
`ifdef SIMULATION
`include "timescale.v"
`endif
module jpeg_encoder(
clk,
ena,
rst,
dstrb,
din,
qnt_val,
qnt_cnt,
size,
rlen,
amp,
douten
);
//
// parameters
//
////////////////////////////////////////////////////////////////////
// //
// ITU-T.81, ITU-T.83 & Coefficient resolution notes //
// //
////////////////////////////////////////////////////////////////////
// //
// Worst case error (all input values -128) is //
// zero (i.e. no errors) when using 15bit coefficients //
// //
// Using less bits for the coefficients produces a biterror //
// approx. equal to (15 - used_coefficient-bits). //
// i.e. 14bit coefficients, errors in dout-bit[0] only //
// 13bit coefficients, errors in dout-bits[1:0] //
// 12bit coefficients, errors in dout-bits[2:0] etc. //
// Tests with real non-continous tone image data have shown that //
// even when using 13bit coefficients errors remain in the lsb //
// only (i.e. dout-bit[0] //
// //
// The amount of coefficient-bits needed is dependent on the //
// desired quality. //
// The JPEG-standard compliance specs.(ITU-T.83) prescribe //
// that the output of the combined DCT AND Quantization unit //
// shall not exceed 1 for the desired quality. //
// //
// This means for high quantization levels, lesser bits //
// for the DCT unit can be used. //
// //
// Looking at the recommended "quantization tables for generic //
// compliance testing of DCT-based processes" (ITU-T.83 annex B) //
// it can be noticed that relatively large quantization values //
// are being used. Errors in the lower-order bits should //
// therefore not be visible. //
// Tests with real continuous and non-continous tone image data //
// have shown that when using the examples quantization tables //
// from ITU-T.81 annex K 10bit coefficients are sufficient to //
// comply to the ITU-T.83 specs. Compliance tests have been met //
// using as little as 9bit coefficients. //
// For certain applications some of the lower-order bits could //
// actually be discarded. When looking at the luminance and //
// chrominance example quantization tables (ITU-T.81 annex K) //
// it can be seen that the smallest quantization value is ten //
// (qnt_val_min = 10). This means that the lowest 2bits can be //
// discarded (set to zero '0') without having any effect on the //
// final result. In this example 11 bit or 12 bit coefficients //
// would be sufficient. //
// //
////////////////////////////////////////////////////////////////////
parameter coef_width = 11;
parameter di_width = 8; // no function yet
//
// inputs & outputs
//
input clk; // system clock
input ena; // clock enable
input rst; // active low asynchronous reset
input dstrb; // data-strobe. Present dstrb 1clk-cycle before data block
input [di_width-1:0] din;
input [7:0] qnt_val; // quantization value
output [ 5:0] qnt_cnt; // quantization value address
output [ 3:0] size; // size
output [ 3:0] rlen; // run-length
output [11:0] amp; // amplitude
output douten; // data output enable
//
// variables
//
wire fdct_doe, qnr_doe;
wire [11:0] fdct_dout;
reg [11:0] dfdct_dout;
wire [10:0] qnr_dout;
reg dqnr_doe;
//
// module body
//
// Hookup FDCT & ZigZag module
fdct #(coef_width, di_width, 12)
fdct_zigzag(
.clk(clk),
.ena(ena),
.rst(rst),
.dstrb(dstrb),
.din(din),
.dout(fdct_dout),
.douten(fdct_doe)
);
// delay 'fdct_dout' => wait for synchronous quantization RAM/ROM
always @(posedge clk)
if(ena)
dfdct_dout <= #1 fdct_dout;
// Hookup QNR (Quantization and Rounding) unit
jpeg_qnr
qnr(
.clk(clk),
.ena(ena),
.rst(rst),
.dstrb(fdct_doe),
.din(dfdct_dout),
.qnt_val(qnt_val),
.qnt_cnt(qnt_cnt),
.dout(qnr_dout),
.douten(qnr_doe)
);
// delay douten 1 clk_cycle => account for delayed fdct_res & qnt_val
always @(posedge clk)
if(ena)
dqnr_doe <= #1 qnr_doe;
//
// TODO: Insert DC differential generator here.
//
wire [11:0] dc_diff_dout = {qnr_dout[10], qnr_dout};
wire dc_diff_doe = dqnr_doe;
// Hookup Run Length Encoder
jpeg_rle
rle(
.clk(clk),
.ena(ena),
.rst(rst),
.dstrb(dc_diff_doe),
.din(dc_diff_dout),
.size(size),
.rlen(rlen),
.amp(amp),
.douten(douten),
.bstart()
);
endmodule
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