C# 中的声音可视化工具
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简单的声音采样器带可视化
引言
这个项目演示了如何使用快速傅里叶变换和 Windows GDI 来生成声音的时域和频域的近实时可视化效果。
背景
在寻找机器人项目信号处理相关信息时，我发现用 C# 编写的示例很难找到。 这促使我创建了一些自己的类，并在此处提供给此演示使用。
Using the Code
此演示的音频输入由 Ianier Munoz 开发的 Wave 类提供。 Wave 样本通过 AudioFrame 类进一步处理。
class AudioFrame
{
private Bitmap _canvasTimeDomain;
private Bitmap _canvasFrequencyDomain;
private double[] _waveLeft;
private double[] _waveRight;
private double[] _fftLeft;
private double[] _fftRight;
private SignalGenerator _signalGenerator;
private bool _isTest = false;
public AudioFrame(bool isTest)
{
_isTest = isTest;
}
/// <summary>
/// Process 16 bit sample
/// </summary>
/// <param name="wave"></param>
public void Process(ref byte[] wave)
{
_waveLeft = new double[wave.Length / 4];
_waveRight = new double[wave.Length / 4];
if (_isTest == false)
{
// Split out channels from sample
int h = 0;
for (int i = 0; i < wave.Length; i += 4)
{
_waveLeft[h] = (double)BitConverter.ToInt16(wave, i);
_waveRight[h] = (double)BitConverter.ToInt16(wave, i + 2);
h++;
}
}
else
{
// Generate artificial sample for testing
_signalGenerator = new SignalGenerator();
_signalGenerator.SetWaveform("Sine");
_signalGenerator.SetSamplingRate(44100);
_signalGenerator.SetSamples(16384);
_signalGenerator.SetFrequency(5000);
_signalGenerator.SetAmplitude(32768);
_waveLeft = _signalGenerator.GenerateSignal();
_waveRight = _signalGenerator.GenerateSignal();
}
// Generate frequency domain data in decibels
_fftLeft = FourierTransform.FFTDb(ref _waveLeft);
_fftRight = FourierTransform.FFTDb(ref _waveRight);
}
/// <summary>
/// Render time domain to PictureBox
/// </summary>
/// <param name="pictureBox"></param>
public void RenderTimeDomain(ref PictureBox pictureBox)
{
// Set up for drawing
_canvasTimeDomain = new Bitmap(pictureBox.Width, pictureBox.Height);
Graphics offScreenDC = Graphics.FromImage(_canvasTimeDomain);
SolidBrush brush = new System.Drawing.SolidBrush
(Color.FromArgb(0, 0, 0));
Pen pen = new System.Drawing.Pen(Color.WhiteSmoke);
// Determine channel boundaries
int width = _canvasTimeDomain.Width;
int center = _canvasTimeDomain.Height / 2;
int height = _canvasTimeDomain.Height;
offScreenDC.DrawLine(pen, 0, center, width, center);
int leftLeft = 0;
int leftTop = 0;
int leftRight = width;
int leftBottom = center - 1;
int rightLeft = 0;
int rightTop = center + 1;
int rightRight = width;
int rightBottom = height;
// Draw left channel
double yCenterLeft = (leftBottom - leftTop) / 2;
double yScaleLeft = 0.5 * (leftBottom - leftTop) / 32768;
// a 16 bit sample has values from -32768 to 32767
int xPrevLeft = 0, yPrevLeft = 0;
for (int xAxis = leftLeft; xAxis < leftRight; xAxis++)
{
int yAxis = (int)(yCenterLeft + (_waveLeft[_waveLeft.Length /
(leftRight - leftLeft) * xAxis] * yScaleLeft));
if (xAxis == 0)
{
xPrevLeft = 0;
yPrevLeft = yAxis;
}
else
{
pen.Color = Color.LimeGreen;
offScreenDC.DrawLine(pen, xPrevLeft, yPrevLeft, xAxis,yAxis);
xPrevLeft = xAxis;
yPrevLeft = yAxis;
}
}
// Draw right channel
int xCenterRight = rightTop + ((rightBottom - rightTop) / 2);
double yScaleRight = 0.5 * (rightBottom - rightTop) / 32768;
// a 16 bit sample has values from -32768 to 32767
int xPrevRight = 0, yPrevRight = 0;
for (int xAxis = rightLeft; xAxis < rightRight; xAxis++)
{
int yAxis = (int)(xCenterRight + (_waveRight[_waveRight.Length /
(rightRight - rightLeft) * xAxis] * yScaleRight));
if (xAxis == 0)
{
xPrevRight = 0;
yPrevRight = yAxis;
}
else
{
pen.Color = Color.LimeGreen;
offScreenDC.DrawLine
(pen, xPrevRight, yPrevRight, xAxis, yAxis);
xPrevRight = xAxis;
yPrevRight = yAxis;
}
}
// Clean up
pictureBox.Image = _canvasTimeDomain;
offScreenDC.Dispose();
}
/// <summary>
/// Render frequency domain to PictureBox
/// </summary>
/// <param name="pictureBox"></param>
public void RenderFrequencyDomain(ref PictureBox pictureBox)
{
// Set up for drawing
_canvasFrequencyDomain = new Bitmap
(pictureBox.Width, pictureBox.Height);
Graphics offScreenDC = Graphics.FromImage(_canvasFrequencyDomain);
SolidBrush brush = new System.Drawing.SolidBrush
(Color.FromArgb(0, 0, 0));
Pen pen = new System.Drawing.Pen(Color.WhiteSmoke);
// Determine channel boundaries
int width = _canvasFrequencyDomain.Width;
int center = _canvasFrequencyDomain.Height / 2;
int height = _canvasFrequencyDomain.Height;
offScreenDC.DrawLine(pen, 0, center, width, center);
int leftLeft = 0;
int leftTop = 0;
int leftRight = width;
int leftBottom = center - 1;
int rightLeft = 0;
int rightTop = center + 1;
int rightRight = width;
int rightBottom = height;
// Draw left channel
for (int xAxis = leftLeft; xAxis < leftRight; xAxis++)
{
double amplitude = (int)_fftLeft[(int)(((double)(_fftLeft.Length)
/ (double)(width)) * xAxis)];
if (amplitude < 0) // Drop negative values
amplitude = 0;
int yAxis = (int)(leftTop +
((leftBottom - leftTop) * amplitude) / 100);
// Arbitrary factor
pen.Color = Color.FromArgb(0, 0, (int)amplitude % 255);
offScreenDC.DrawLine(pen, xAxis, leftTop, xAxis, yAxis);
}
// Draw right channel
for (int xAxis = rightLeft; xAxis < rightRight; xAxis++)
{
double amplitude = (int)_fftRight[(int)(((double)
(_fftRight.Length) / (double)(width)) * xAxis)];
if (amplitude < 0)
amplitude = 0;
int yAxis = (int)(rightBottom -
((rightBottom - rightTop) * amplitude) / 100);
pen.Color = Color.FromArgb(0, 0, (int)amplitude % 255);
offScreenDC.DrawLine(pen, xAxis, rightBottom, xAxis, yAxis);
}
// Clean up
pictureBox.Image = _canvasFrequencyDomain;
offScreenDC.Dispose();
}
}