cvsd_decode.m

CVCD编解码的matlab仿真： CVSD文档+matlab仿真程序

% 07.11.5
% lidongshi
% cvsd decode
%

function [cvsd_decode_data,sw_enc_bit_dly_1,sw_enc_bit_dly_2,sw_step,sw_rcnstrct_dly_1,sw_rcnstrct_dly_2] = cvsd_decode(sw_enc_bit,sw_enc_bit_dly_1,sw_enc_bit_dly_2,sw_step,sw_rcnstrct_dly_1,sw_rcnstrct_dly_2)

DELTA_MIN = 0.0002;%4;		% 0.0002 Scaled to 2 ^ 14
DELTA_MAX = 0.0078;%128;     % 0.0078 Scaled to 2 ^ 14
SYLLABIC_CONST = 0.9845;%32260;   % 0.9845 Scaled to 2 ^ 15
INTEG_B1 = 1.2708;%20821;   % 1.2708 Scaled to 2 ^ 14
INTEG_B2 = 0.3202;%10492;   % 0.3202 Scaled to 2 ^ 15
INTEG_G2D = 1.5092;%24726;   % 1.5092 Scaled to 2 ^ 14

% sw_enc_bit_dly_1 = 0;
% sw_enc_bit_dly_2 = 0;
% sw_step = 0;
% sw_rcnstrct_dly_1 = 0;
% sw_rcnstrct_dly_2 = 0;

% 	int sw_acc;
% 	int sw_rcnstrct;
% 	
% 	long int tmp1;
% 	long int tmp2;
% 	long int tmp3;
% 	int tmp4;
tmp_lds_1 = 0;
tmp_lds_2 = 0;
tmp_lds_3 = 0;
%  Judging continuous three bit identity and syllablic filter
sw_enc_bit = 2 * sw_enc_bit - 1;   % 0 --> -1; 1 --> 1

sw_acc = sw_enc_bit + sw_enc_bit_dly_1 + sw_enc_bit_dly_2;

tmp_lds_1 = sw_step;
tmp1 = SYLLABIC_CONST * tmp_lds_1;
% 	//tmp1 = (SYLLABIC_CONST * sw_step);
% 	tmp1 >>= 15;
	
if abs(sw_acc) == 3
	sw_step = tmp1 + DELTA_MAX;
else
	sw_step = tmp1 + DELTA_MIN;
end
% 	Primary reconstruction integration
tmp_lds_2 = sw_rcnstrct_dly_1;
tmp1 = INTEG_B1 * tmp_lds_2;
% 	//tmp1 = INTEG_B1 * sw_rcnstrct_dly_1;
% 	tmp1 >>= 14;
tmp_lds_2 = sw_rcnstrct_dly_2;
tmp2 = INTEG_B2 * tmp_lds_2;
% 	//tmp2 = INTEG_B2 * sw_rcnstrct_dly_2;
% 	tmp2 >>= 15;
tmp_lds_1 = sw_step;
tmp3 = INTEG_G2D * tmp_lds_1;
% 	//tmp3 = INTEG_G2D * sw_step;
% 	tmp4 = tmp3 >> (14 + 1);           % '14' add '1' for normalization
tmp3 = tmp3 * sw_enc_bit;

tmp1 = tmp1 - tmp2 + tmp3;

% 	Saturation process
if (tmp1 >= 32767)        % up overflow
	sw_rcnstrct = 32767;
elseif (tmp1 <= -32768)  % down overflow
	sw_rcnstrct = -32768;
else                      % no overflow
	sw_rcnstrct = tmp1;
end
	
% 	Shift register shift
sw_enc_bit_dly_2 = sw_enc_bit_dly_1;
sw_enc_bit_dly_1 = sw_enc_bit;

sw_rcnstrct_dly_2 = sw_rcnstrct_dly_1;
sw_rcnstrct_dly_1 = sw_rcnstrct;
	
% return (sw_rcnstrct);
cvsd_decode_data = sw_rcnstrct;