我制作了此SoundAnalyzer类来检测歌曲中的节拍:
class SoundAnalyzer
{
public SoundBuffer soundData;
public Sound sound;
public List<double> beatMarkers = new List<double>();
public SoundAnalyzer(string path)
{
soundData = new SoundBuffer(path);
sound = new Sound(soundData);
}
// C = threshold, N = size of history buffer / 1024 B = bands
public void PlaceBeatMarkers(float C, int N, int B)
{
List<double>[] instantEnergyList = new List<double>[B];
GetEnergyList(B, ref instantEnergyList);
for (int i = 0; i < B; i++)
{
PlaceMarkers(instantEnergyList[i], N, C);
}
beatMarkers.Sort();
}
private short[] getRange(int begin, int end, short[] array)
{
short[] result = new short[end - begin];
for (int i = 0; i < end - begin; i++)
{
result[i] = array[begin + i];
}
return result;
}
// get a array of with a list of energy for each band
private void GetEnergyList(int B, ref List<double>[] instantEnergyList)
{
for (int i = 0; i < B; i++)
{
instantEnergyList[i] = new List<double>();
}
short[] samples = soundData.Samples;
float timePerSample = 1 / (float)soundData.SampleRate;
int sampleIndex = 0;
int nextSamples = 1024;
int samplesPerBand = nextSamples / B;
// for the whole song
while (sampleIndex + nextSamples < samples.Length)
{
complex[] FFT = FastFourier.Calculate(getRange(sampleIndex, nextSamples + sampleIndex, samples));
// foreach band
for (int i = 0; i < B; i++)
{
double energy = 0;
for (int j = 0; j < samplesPerBand; j++)
energy += FFT[i * samplesPerBand + j].GetMagnitude();
energy /= samplesPerBand;
instantEnergyList[i].Add(energy);
}
if (sampleIndex + nextSamples >= samples.Length)
nextSamples = samples.Length - sampleIndex - 1;
sampleIndex += nextSamples;
samplesPerBand = nextSamples / B;
}
}
// place the actual markers
private void PlaceMarkers(List<double> instantEnergyList, int N, float C)
{
double timePerSample = 1 / (double)soundData.SampleRate;
int index = N;
int numInBuffer = index;
double historyBuffer = 0;
//Fill the history buffer with n * instant energy
for (int i = 0; i < index; i++)
{
historyBuffer += instantEnergyList[i];
}
// If instantEnergy / samples in buffer < instantEnergy for the next sample then add beatmarker.
while (index + 1 < instantEnergyList.Count)
{
if(instantEnergyList[index + 1] > (historyBuffer / numInBuffer) * C)
beatMarkers.Add((index + 1) * 1024 * timePerSample);
historyBuffer -= instantEnergyList[index - numInBuffer];
historyBuffer += instantEnergyList[index + 1];
index++;
}
}
}
由于某种原因,它只能检测到637秒到641秒左右的节拍,我不知道为什么。我知道节拍是从多个频段插入的,因为我发现重复项,而且似乎正在为这些值之间的每个瞬时能量值分配节拍。
它是在此之后建模的:http : //www.flipcode.com/misc/BeatDetectionAlgorithms.pdf
那为什么节拍不能正确记录呢?
2
您可以发布一个频段随时间变化的InstantEnergyList [index + 1]和historyBuffer的图吗?这两个图彼此重叠。这样可以提供有关问题可能出在哪里的线索。同样,能量必须是大小的平方,请不要忘记这一点。
—
CeeJay 2011年
嗯,是的,这可能会揭示问题,让我看看我是否可以以某种方式绘制图表
—
Quincy
但是此图只是historyBuffer或historyBuffer / numInBuffer * C吗?似乎您的计算机中有大量C。查看代码,historyBuffer应该具有与InstantEnergy类似的值,该图只能在C太高或numInBuffer太低(远低于1)时出现,我猜不是这样。
—
CeeJay 2011年
不会死的问题...
—
工程师