在VS上用c语言写FIR滤波器

下面是一个使用C语言在Visual Studio上实现的FIR滤波器的示例代码：

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define SAMPLE_RATE 44100
#define FILTER_FREQ 1000

double filterCoefficients[101];

void generateFilterCoefficients()
{
    int filterLength = 100;
    double cutoffFreq = FILTER_FREQ / ((double)SAMPLE_RATE / 2);

    for (int n = 0; n <= filterLength; n++) {
        if (n == filterLength / 2) {
            filterCoefficients[n] = 2 * M_PI * cutoffFreq;
        }
        else {
            filterCoefficients[n] = sin(2 * M_PI * cutoffFreq * (n - filterLength / 2)) / (M_PI * (n - filterLength / 2));
        }
        filterCoefficients[n] *= 0.54 - 0.46 * cos(2 * M_PI * n / filterLength);
    }
}

double filterSample(double sample)
{
    static double delayLine[101] = { 0 };
    double outputSample = 0;

    delayLine[0] = sample;

    for (int n = 0; n <= 100; n++) {
        outputSample += filterCoefficients[n] * delayLine[n];
    }

    for (int n = 100; n >= 1; n--) {
        delayLine[n] = delayLine[n - 1];
    }

    return outputSample;
}

int main()
{
    generateFilterCoefficients();

    // test the filter on a sine wave
    double frequency = 500;
    double amplitude = 10000;
    double phase = 0;
    double time = 0;
    double sample;
    double filteredSample;

    for (int i = 0; i < SAMPLE_RATE; i++) {
        sample = amplitude * sin(2 * M_PI * frequency * time + phase);
        filteredSample = filterSample(sample);
        printf("%d, %f, %f\n", i, sample, filteredSample);
        time += 1 / (double)SAMPLE_RATE;
    }

    return 0;
}

这个示例代码实现了一个100阶的低通FIR滤波器，截止频率为1000Hz，样本率为44100Hz。`generateFilterCoefficients()`函数生成了FIR滤波器的系数，`filterSample()`函数对每个输入样本进行滤波，并返回输出样本。在`main()`函数中，我们测试了这个滤波器在500Hz正弦波上的效果。最终输出的结果包括样本序号、输入样本值和输出样本值。你可以根据自己的需要修改截止频率、滤波器阶数、样本率等参数。