【NAudio】AF Spectrum Analyzer
- atliqu
- 2023年6月17日
AFアンプやフィルタの周波数を特性を見るためにAF帯のスペアナが欲しかったので、作成してみた。
1kHzの信号を測定している様子。 21kHzぐらいにも信号が出ているけど、原因は不明。
NAudioのWaveInとFastFourierTransformを使った。
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using System; using System.Drawing; using System.Windows.Forms; using NAudio.Wave; using NAudio.Dsp; namespace NAudioTest { public partial class Form1 : Form { public Form1() { InitializeComponent(); } WaveIn waveIn; float[] fftdata; bool dataready; int pb_height, pb_width; float xtick, ytick, offset, fstep; private void Form1_Load(object sender, EventArgs e) { waveIn = new WaveIn() { DeviceNumber = 0, // Default }; waveIn.DataAvailable += WaveIn_DataAvailable; waveIn.BufferMilliseconds = 200; //200ms waveIn.WaveFormat = new WaveFormat(44100, 2); //data siza 44100 * 200ms = 8820サンプル, FFTではこの内8192サンプルだけ使う waveIn.StartRecording(); dataready = false; pb_height = pictureBox1.Height - 1; pb_width = pictureBox1.Width - 1; xtick = pb_width / (float)(Math.Log10(22100) - Math.Log10(50)); //左端 50HZ、右端 22100Hz ytick = pb_height / 10f; //相対値 offset = (float)Math.Log10(50); fstep = 44100f / 8192f; } private float[] FFT_NAudio(float[] sdata) { var fftsample = new Complex[sdata.Length]; var res = new float[sdata.Length / 2]; //複素数に変換、ハミング窓かけ for (int i = 0; i < sdata.Length; i++) { fftsample[i].X = (float)(sdata[i] * FastFourierTransform.HammingWindow(i, sdata.Length)); fftsample[i].Y = 0; } FastFourierTransform.FFT(true, 13, fftsample); //絶体値をdBに変換 for (int i = 0; i < sdata.Length / 2; i++) { res[i] = 20 * (float)Math.Log(Math.Sqrt(fftsample[i].X * fftsample[i].X + fftsample[i].Y * fftsample[i].Y)); } return res; } private void WaveIn_DataAvailable(object sender, WaveInEventArgs e) { short[] sdata = new short[8820]; float[] snddata = new float[8192]; for (int index = 0; index < e.BytesRecorded; index += 4) sdata[index / 4] = (short)((e.Buffer[index + 1] << 8) | e.Buffer[index + 0]); Array.Copy(sdata, snddata, 8192); fftdata = FFT_NAudio(snddata); dataready = true; pictureBox1.Refresh(); } private void panel1_Paint(object sender, PaintEventArgs e) { SolidBrush br = new SolidBrush(Color.Black); Font ft = new Font("MS UI Gothic", 9); for (int i = 1; i < 5; i++) { string st = (i * 200).ToString(); PointF pt = new PointF(xtick * (float)(Math.Log10(200 * i) - offset) - 10, panel1.Height - 20); 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) - 10, panel1.Height - 20); 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) - 10, panel1.Height - 20); e.Graphics.DrawString(st, ft, br, pt); } } private void pictureBox1_Paint(object sender, PaintEventArgs e) { DrawAxis(e.Graphics); if(dataready) { DrawSpectrum(e.Graphics, fftdata); } } 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 Form1_FormClosed(object sender, FormClosedEventArgs e) { dataready = false; waveIn?.StopRecording(); waveIn?.Dispose(); waveIn = null; } private void DrawSpectrum(Graphics gr, float[] data) { PointF oldPoint = new PointF(); PointF newPoint = new PointF(); oldPoint.X = (float)(Math.Log10(fstep) - offset); oldPoint.Y = pb_height - data[1]; for(int i = 2; i < 4096; i++) { newPoint.X = xtick * (float)(Math.Log10(fstep * i) - offset); newPoint.Y = pb_height / 2 - data[i]; gr.DrawLine(Pens.Red, oldPoint, newPoint); oldPoint = newPoint; } } } } |
logで目盛りを付けるところが一番時間がかかった。 もっと賢い方法があるかもしれないなぁ．．。
トラッキングジェネレータを作りたいんだけど、どうやって同期を取るかノーアイデア．．。