expanderint16clip.m

模拟语音信号的动态范围解压缩算法的matlab源码

function [y,G_out] = expanderINT16clip(x,Fd,G_in,M)
%expander
% y = expanderINT16clip(x,Fd,G_in,M)
%x      -- the input signal array
%Fd     -- the full deviated amplitude
%G_in   -- the initial Gain
%M      -- update the expander gain every M samples
%
%y      -- the expanded signal array
%G_out  -- the output Gain
%
%Companding Specificationn
%      Compression Ratio 2:1
%      Crossover Point   60% of full audio deviation
%      Attack Time       3.3 ms
%      Recovery Time     14.85 ms
%
%
INT16_SCALE = 32768;

persistent ae ae_1 average counter mean old_x_array ae1 ae1_1 ae2 ae2_1 ae_diff ae_diff_1;

%initialization
if isempty(ae)
    ae1 = float2Fract(0.99436);
    ae1_1 = 2^31 - fract2LongFract(ae1); %float2LongFract((1-0.99436));
    ae2 = float2Fract(0.99985);
    ae2_1 = 2^31 - fract2LongFract(ae2); %float2LongFract((1-0.99985));
    
    ae_diff = float2Fract(0.9995);
    ae_diff_1 = 2^31 - fract2LongFract(ae_diff);
      
    counter = 0;
    average = 0;
    mean = 0;
    old_x_array = zeros(1,40);
end

Ue = fractMult(float2Fract(0.6366),Fd);
ae = ae1;
ae_1 = ae1_1;

global mean_e_g average_e_g diff_e_g avg_dif_e_g Ge_g flag_e_g avg_dif_float_e_g;      %test only

avg_dif = 0;
avg_dif_float = 0;                                %test only
OneForty = float2Fract(1/40);
temp1 = 0;
temp2 = 0;
scale_flag = 0;

for i = 1:length(x)
    abstract = abs(x(i));
  
    temp1 = longLongFractMult(temp1,ae) + longLongFractMult(ae_1,abstract);       %averager. divide 2^15 for fractional multiplication.
    average = longFract2Fract(temp1);
    
    average_e_g(i) = average;                       %test only
    
    mean = mean - fractMult(OneForty,old_x_array(1)) + fractMult(OneForty,abstract);    %update mean
    
    mean_e_g(i)= mean;                              %test only
    
    if counter == 0                             %update gain every M times     
        G_in = average/Ue;
        G_in_floor = floor(G_in);
        G_in_fract = float2Fract(G_in - floor(G_in));
        counter = M;
    end
    
    Ge_g(i) = G_in;                                     %test only
    
    old_x_array(1:39) = old_x_array(2:40);
    old_x_array(40) = abs(x(i));
    
    difference = abs(mean-average);
    
    diff_e_g(i) = difference;                     %test only
    average_e_g(i) = average;                     %test only
    
    if difference > fractMult(mean,float2Fract(0.1))        %0.1*mean
        avg_dif = fract2LongFract(difference);        %scale up 6 bits to prevent fix-point effect in calculating average difference
        avg_dif_float = difference;              %test only
        ae = ae1;
        ae_1 = ae1_1;
        
        flag_e_g(i) = 0;                          %test only
    else
        avg_dif = longLongFractMult(ae_diff_1,difference) + longLongFractMult(avg_dif,ae_diff);
        avg_dif_float = difference + 0.9995*(avg_dif_float-difference);   %test only
        
        if avg_dif < longLongFractMult(float2LongFract(0.04),mean)
            ae = ae2;
            ae_1 = ae2_1;
            flag_e_g(i) = 1000;                    %test only
        else
            ae = ae1;
            ae_1 = ae1_1;
            flag_e_g(i) = 0;                       %test only
        end
    end
    
    avg_dif_e_g(i) = avg_dif;                     %test only
    avg_dif_float_e_g(i) = avg_dif_float;         %test only
    
    counter = counter - 1;
    
    temp = fractMultInt(x(i),G_in_floor) + fractMult(G_in_fract,x(i));
    if temp >= INT16_SCALE - 1
        temp = INT16_SCALE - 1;
    end
    if temp < -INT16_SCALE
        temp = -INT16_SCALE;
    end
    y(i) = temp;
end

G_out = G_in;                               %store the current gain