【NAudio】教科書のFFTでやってみた
- atliqu
- 2023年6月25日
昨日の続き。
「C#によるデジタル信号処理プログラミング」という著書にあるFFTで実行した結果。
NAudio.DSPにあるFFTよりノイズが少ないみたい。
こっちを使うことにする。 ちなみに肝心のFFT処理の部分は、上記本に記載されているコードそのものなのでここでは公開しない。
その他のソース
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using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Forms; using NAudio.Wave; using System.Numerics; namespace RealFFT { public partial class Form1 : Form { public Form1() { InitializeComponent(); } WaveIn wavein; FftReal myFFT; double[] capdata0, capdata1, wHm, dBdata; bool toggle,dataready; int pb_height, pb_width; float xtick, ytick, offset, fstep; private void Form1_Load(object sender, EventArgs e) { wavein = new WaveIn(); myFFT = new FftReal(8192); wavein.DataAvailable += wavein_DataAvailable; wavein.BufferMilliseconds = 180; //180ms wavein.WaveFormat = new WaveFormat(45511, 2); //data siza 45511 * 180ms = 8191サンプル wavein.StartRecording(); wHm = getHammingWnd(); //Hamming窓生成 toggle = true; dataready = false; pb_height = pictureBox1.Height - 1; pb_width = pictureBox1.Width - 1; xtick = pb_width / (float)(Math.Log10(22756) - Math.Log10(50)); //左端 50HZ、右端 22756Hz ytick = pb_height / 10f; //相対値 offset = (float)Math.Log10(50); fstep = 45511f / 8192f; capdata0 = new double[8192]; capdata1 = new double[8192]; dBdata = new double[4096]; } private void Form1_FormClosed(object sender, FormClosedEventArgs e) { dataready = false; wavein?.StopRecording(); wavein?.Dispose(); wavein = null; } private void wavein_DataAvailable(object sender, WaveInEventArgs e) { short[] datas = new short[8192]; double[] datad = new double[8192]; double[] fftdata = new double[8192]; Complex[] spc = new Complex[4096]; for(int i = 0; i < e.BytesRecorded; i += 4) { datas[i / 4] = (short)((e.Buffer[i + 1] << 8) | e.Buffer[i + 0]); datad[i / 4] = datas[i / 4] * wHm[i / 4]; } if(toggle) { datad.CopyTo(capdata0, 0); Array.Copy(capdata0, 4096, fftdata, 0, 4096); Array.Copy(capdata1, 0, fftdata, 4096, 4096); spc = myFFT.ExecuteFft(fftdata); for (int i = 0; i < spc.Length; i++) { dBdata[i] = (float)(10 * Math.Log(spc[i].Real * spc[i].Real + spc[i].Imaginary * spc[i].Imaginary)); } dataready = true; pictureBox1.Invalidate(); } else { datad.CopyTo(capdata1, 0); Array.Copy(capdata0, 0, fftdata, 4096, 4096); Array.Copy(capdata1, 4096, fftdata, 0, 4096); spc = myFFT.ExecuteFft(fftdata); for (int i = 0; i < spc.Length; i++) { dBdata[i] = (float)(10 * Math.Log(spc[i].Real * spc[i].Real + spc[i].Imaginary * spc[i].Imaginary)); } dataready = true; pictureBox1.Invalidate(); } spc = myFFT.ExecuteFft(datad); for (int i = 0; i < spc.Length; i++) { dBdata[i] = (float)(10 * Math.Log(spc[i].Real * spc[i].Real + spc[i].Imaginary * spc[i].Imaginary)); } pictureBox1.Invalidate(); toggle = !toggle; } //Hamming窓生成 private double[] getHammingWnd() { double[] res = new double[8192]; for (int i = 0; i < 8192; i++) res[i] = 0.54 - 0.46 * Math.Cos(2.0 * Math.PI * i / 8192); return res; } private void pictureBox1_Paint(object sender, PaintEventArgs e) { DrawAxis(e.Graphics); if (dataready) { DrawSpectrum(e.Graphics, dBdata); } } private void panel1_Paint(object sender, PaintEventArgs e) { SolidBrush br = new SolidBrush(Color.Black); Font ft = new Font("MS UI Gothic", 9); int y_offset = 25; float x_offset = 15f; for (int i = 1; i < 5; i++) { string st = (i * 200).ToString(); PointF pt = new PointF(xtick * (float)(Math.Log10(200 * i) - offset) + x_offset, panel1.Height - y_offset); e.Graphics.DrawString(st, ft, br, pt); } for (int i = 1; i < 3; i++) { string st = (i * 2).ToString() + "k"; PointF pt = new PointF(xtick * (float)(Math.Log10(2000 * i) - offset) + x_offset, panel1.Height - y_offset); e.Graphics.DrawString(st, ft, br, pt); } for (int i = 1; i < 3; i++) { string st = (i * 10).ToString() + "k"; PointF pt = new PointF(xtick * (float)(Math.Log10(10000 * i) - offset) + x_offset, panel1.Height - y_offset); e.Graphics.DrawString(st, ft, br, pt); } } public void DrawAxis(Graphics gr) { gr.DrawLine(Pens.Black, 0, pb_height, 0, 0); gr.DrawLine(Pens.Black, pb_width, pb_height, pb_width, 0); //100Hz～1000Hz 100Hzステップ for (int i = 1; i < 11; i++) gr.DrawLine(Pens.Black, xtick * (float)(Math.Log10(100 * i) - offset), pb_height, xtick * (float)(Math.Log10(100 * i) - offset), 0); //2000Hz～22000Hz 1000Hzステップ for (int i = 2; i < 22; i = i + 2) gr.DrawLine(Pens.Black, xtick * (float)(Math.Log10(1000 * i) - offset), pb_height, xtick * (float)(Math.Log10(1000 * i) - offset), 0); //縦軸 for (int i = 0; i <= 10; i++) gr.DrawLine(Pens.Black, 0, ytick * i, pb_width, ytick * i); } private void DrawSpectrum(Graphics gr, double[] data) { PointF oldPoint = new PointF(); PointF newPoint = new PointF(); oldPoint.X = (float)(Math.Log10(fstep) - offset); oldPoint.Y = (float)(pb_height - data[1]); for (int i = 2; i < 4096; i++) { newPoint.X = xtick * (float)(Math.Log10(fstep * i) - offset); newPoint.Y = (float)(pb_height - data[i]); gr.DrawLine(Pens.Red, oldPoint, newPoint); oldPoint = newPoint; } } } } |
やり方は、NAudioのFFTを使ったものとほぼ同じ。 サンプルレート45511、FFTデータ数8192、ハミング窓、重複処理。
WaveInの処理は、winmmを使うより圧倒的に便利なのでNAudioを使う。