我已经为音频信号的频率调制写了下面的代码。音频本身是1秒长,以8000赫兹采样。我想通过使用频率为50 Hz的正弦波(表示为采样频率的一部分)将FM应用于此音频信号。调制信号的调制指数为0.25,以便只产生一对边带。调频(FM)代码片段
for (i = 0; i < 7999; i++) {
phi_delta = 8000 - 8000 * (1 + 0.25 * sin(2* pi * mf * i));
f_phi_accum += phi_delta; //this can have a negative value
/*keep only the integer part that'll be used as an index into the input array*/
i_phi_accum = f_phi_accum;
/*keep only the fractional part that'll be used to interpolate between samples*/
r_phi_accum = f_phi_accum - i_phi_accum;
//If I'm getting negative values should I convert them to positive
//r_phi_accum = fabs(f_phi_accum - i_phi_accum);
i_phi_accum = abs(i_phi_accum);
/*since i_phi_accum often exceeds 7999 I have to add this if statement so as to prevent out of bounds errors */
if (i_phi_accum < 7999)
output[i] = ((input[i_phi_accum] + input[i_phi_accum + 1])/2) * r_phi_accum;
}
好的,但是你的问题是什么? – 2011-12-30 09:09:48
那么,这段代码似乎并没有工作,我甚至不知道它是否应该工作。我在另一个线程(http://stackoverflow.com/questions/8655121/frequency-modulation-fm)问这个问题,只是试图实现我在那里被告知。 – 2011-12-30 09:30:07