%語音信號的端點檢測
[x,fs,nbits]=wavread('speech.wav');
x = x / max(abs(x));%幅度歸一化到[-1,1]
%參數設置
FrameLen = 256;     %幀長
inc = 90;           %未重疊部分

amp1 = 10;          %短時能量閾值
amp2 = 2;      
zcr1 = 10;          %過零率閾值
zcr2 = 5;

minsilence = 6;  %用無聲的長度來判斷語音是否結束
minlen  = 15;    %判斷是語音的最小長度
status  = 0;     %記錄語音段的狀態
count   = 0;     %語音序列的長度
silence = 0;     %無聲的長度

%計算過零率
tmp1  = enframe(x(1:end-1), FrameLen,inc);
tmp2  = enframe(x(2:end)  , FrameLen,inc);
signs = (tmp1.*tmp2)<0;
diffs = (tmp1 -tmp2)>0.02;
zcr   = sum(signs.*diffs,2);

%計算短時能量
amp = sum((abs(enframe(filter([1 -0.9375], 1, x), FrameLen, inc))).^2, 2);

%調整能量門限
amp1 = min(amp1, max(amp)/4);
amp2 = min(amp2, max(amp)/8);

%開始端點檢測
for n=1:length(zcr)
   goto = 0;
   switch status
   case {0,1}                   % 0 = 靜音, 1 = 可能開始
      if amp(n) > amp1          % 確信進入語音段
         x1 = max(n-count-1,1); % 記錄語音段的起始點
         status  = 2;
         silence = 0;
         count   = count + 1;
      elseif amp(n) > amp2 || zcr(n) > zcr2 % 可能處于語音段
         status = 1;
         count  = count + 1;
      else                       % 靜音狀態
         status  = 0;
         count   = 0;
      end
   case 2,                       % 2 = 語音段
      if amp(n) > amp2 ||zcr(n) > zcr2     % 保持在語音段
         
         count = count + 1;
      else                       % 語音將結束
         silence = silence+1;
         if silence < minsilence % 靜音還不夠長，尚未結束
            count  = count + 1;
         elseif count < minlen   % 語音長度太短，認為是噪聲
            status  = 0;
            silence = 0;
            count   = 0;
         else                    % 語音結束
            status  = 3;
         end
      end
   case 3,
      break;
   end
end   

count = count-silence/2;
x2 = x1 + count -1;              %記錄語音段結束點

subplot(3,1,1)
plot(x)
axis([1 length(x) -1 1])
ylabel('Speech');
line([x1*inc x1*inc], [-1 1], 'Color', 'red');
line([x2*inc x2*inc], [-1 1], 'Color', 'red');

subplot(3,1,2)
plot(amp);
axis([1 length(amp) 0 max(amp)])
ylabel('Energy');
line([x1 x1], [min(amp),max(amp)], 'Color', 'red');
line([x2 x2], [min(amp),max(amp)], 'Color', 'red');

subplot(3,1,3)
plot(zcr);
axis([1 length(zcr) 0 max(zcr)])
ylabel('ZCR');
line([x1 x1], [min(zcr),max(zcr)], 'Color', 'red');
line([x2 x2], [min(zcr),max(zcr)], 'Color', 'red');