我正在尝试创建一个正弦波振荡器来播放音频源。
起初，我创建了一个简单的，如下所示：
public class FirstOscillator : MonoBehaviour
{
public double frequency = 400.0;
private double increment;
private double phase;
private double sampleRate = 48000.0;
public float gain;
void OnAudioFilterRead(float[] data, int channels)
{
increment = frequency * 2.0 * Mathf.PI / sampleRate;
for (int i = 0; i < data.Length; i += channels)
{
phase += increment;
data[i] = (float) (gain * Mathf.Sin((float) phase));
if (channels == 2)
{
data[i + 1] = data[i];
}
}
}
}
这工作得很好，并产生一个听起来不错的正弦波。
但是我决定从设计上讲，我的振荡器最好是amplitude(frequency, time)函数，所以我试图修改它以实际使用时间并将振荡提取到一种方法中：
public class SecondOscillator : MonoBehaviour, IAudioFilter
{
public double frequency = 400.0;
private double sampleRate = 48000.0;
public float gain;
public void OnAudioFilterRead(float[] data, int channels)
{
var time = AudioSettings.dspTime;
for (int i = 0; i < data.Length; i += channels)
{
data[i] = gain * Amplitude((float)frequency, (float)(time + i / sampleRate / channels));
if (channels == 2)
{
data[i + 1] = data[i];
}
}
}
private float Amplitude(float freq, float time)
{
return Mathf.Sin(freq * time * 2 * Mathf.PI);
}
}
出于某种原因，这会产生听起来奇怪的金属噪音，但会对频率变化做出反应。我想知道可能是什么问题。
更新
在评论部分，人们建议AudioSettings.dspTime是多个样本，而不是以秒为单位的时间。我认为情况并非如此，所以我编写了一个快速脚本来测试它：
class SampleRateTest : MonoBehaviour
{
public int sampleRate;
public void Awake()
{
sampleRate = AudioSettings.outputSampleRate;
}
private StringBuilder sb = new StringBuilder();
private int samplesTakenStart = 5;
private int samplesTakenEnd = 5;
private int loggedFrames = 5;
private int loggedFrameIndex = 0;
public void OnAudioFilterRead(float[] data, int channels)
{
var time = AudioSettings.dspTime;
for (var index = 0; index < data.Length; index++)
{
if (index < samplesTakenStart || index > data.Length - samplesTakenEnd)
sb.AppendLine($"Sample {index} time is {time}");
else if (index == samplesTakenStart)
sb.AppendLine("...");
time += 1.0 / sampleRate / channels;
}
sb.AppendLine("End of frame " + loggedFrameIndex);
if (loggedFrameIndex++ == loggedFrames)
Debug.Log(sb.ToString());
}
}
这将生成以下输出：
Sample 0 time is 1196.144
Sample 1 time is 1196.14401041667
Sample 2 time is 1196.14402083333
Sample 3 time is 1196.14403125
Sample 4 time is 1196.14404166667
...
Sample 508 time is 1196.14929166661
Sample 509 time is 1196.14930208328
Sample 510 time is 1196.14931249994
Sample 511 time is 1196.14932291661
End of frame 0
Sample 0 time is 1196.14933333333
Sample 1 time is 1196.14934375
Sample 2 time is 1196.14935416667
Sample 3 time is 1196.14936458333
Sample 4 time is 1196.149375
...
Sample 508 time is 1196.15462499994
Sample 509 time is 1196.15463541661
Sample 510 time is 1196.15464583328
Sample 511 time is 1196.15465624994
End of frame 1
Sample 0 time is 1196.15466666667
Sample 1 time is 1196.15467708333
Sample 2 time is 1196.1546875
Sample 3 time is 1196.15469791667
Sample 4 time is 1196.15470833333
...
Sample 508 time is 1196.15995833328
Sample 509 time is 1196.15996874994
Sample 510 time is 1196.15997916661
Sample 511 time is 1196.15998958328
End of frame 2
Sample 0 time is 1196.16
Sample 1 time is 1196.16001041667
Sample 2 time is 1196.16002083333
Sample 3 time is 1196.16003125
Sample 4 time is 1196.16004166667
...
Sample 508 time is 1196.16529166661
Sample 509 time is 1196.16530208328
Sample 510 time is 1196.16531249994
Sample 511 time is 1196.16532291661
End of frame 3
Sample 0 time is 1196.16533333333
Sample 1 time is 1196.16534375
Sample 2 time is 1196.16535416667
Sample 3 time is 1196.16536458333
Sample 4 time is 1196.165375
...
Sample 508 time is 1196.17062499994
Sample 509 time is 1196.17063541661
Sample 510 time is 1196.17064583328
Sample 511 time is 1196.17065624994
End of frame 4
Sample 0 time is 1196.17066666667
Sample 1 time is 1196.17067708333
Sample 2 time is 1196.1706875
Sample 3 time is 1196.17069791667
Sample 4 time is 1196.17070833333
...
Sample 508 time is 1196.17595833328
Sample 509 time is 1196.17596874994
Sample 510 time is 1196.17597916661
Sample 511 time is 1196.17598958328
End of frame 5
所以对我来说，看起来AudioSettings.dspTime确实是时间，所以它不应该被sampleRate除以。如果这很重要，我的系统上的channels计数是 2。
更新2：我还尝试删除特定于通道的代码并将项目音频设置设置为单声道(而不是立体声(，但这没有帮助，所以我认为通道不是这里的问题。
此外，我创建了我获得的声音的wav演示。对我来说，这听起来更像是一个正方形而不是正弦。
哦。我。神。问题是我使用的是float值而不是double，而且浮点计算对于此类数据来说似乎不够精确。将我所有的浮标都更改为双打，现在可以工作了。