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Sound Activated Recorder with Spectrogram in C#

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4.92/5 (54 votes)
27 Jan 2008GPL3 398.9K   32.1K   207   105
Audio event processing with visual display
SoundCatcher

Introduction

This project demonstrates an implementation of the waterfall spectrogram and use of statistical data to trigger events in near real-time. This code is an elaboration of my previous submission (SoundViewer). This demonstration utilizes the Wave classes developed by Ianier Munoz.

Using the Code

Audio is supplied by the default input device which is typically the microphone. Events are triggered when audio amplitude exceeds the desired threshold value, which can be set under Options on the menu bar. To make this more useful, I've added functionality to save the stream to disk which results in a nice sound activated recorder.

Points of Interest

In order to draw the spectrogram fast enough to allow for near real-time operation, I needed to write directly to memory using unsafe code.

C#
// lock image
PixelFormat format = canvas.PixelFormat;
BitmapData data = 
    canvas.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadOnly, format);
int stride = data.Stride;
int offset = stride - width * 4;

// draw image
try
{
  unsafe
  {
    byte* pixel = (byte*)data.Scan0.ToPointer();
    // for each column
    for (int y = 0; y <= height; y++)
    {
      if (y < _fftLeftSpect.Count)
      {
        // for each row
        for (int x = 0; x < width; x++, pixel += 4)
        {
          double amplitude = ((double[])_fftLeftSpect[_fftLeftSpect.Count - y - 1])
                [(int)(((double)(_fftLeft.Length) / (double)(width)) * x)];
          double color = GetColor(min, max, range, amplitude);
          pixel[0] = (byte)0;
          pixel[1] = (byte)color;
          pixel[2] = (byte)0;
          pixel[3] = (byte)255;
        }
        pixel += offset;
      }
    }
  }
}
catch (Exception ex)
{
  Console.WriteLine(ex.ToString());
}

// unlock image
canvas.UnlockBits(data);

I noticed that the results vary wildly depending on the hardware and associated drivers being used.

Some things I'd like to experiment with further when I get the time:

  1. Use of frequency domain to produce "motion" detector equivalent
  2. Use of spectrogram in sound identification
  3. Improving performance/robustness

History

  • 01/16/2008: Created

License

This article, along with any associated source code and files, is licensed under The GNU General Public License (GPLv3)


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Comments and Discussions

 
GeneralMy vote of 5 Pin
Nasenbaaer12-May-21 9:33
Nasenbaaer12-May-21 9:33 
QuestionSoundcatcher have an issue Pin
Member 109051932-Mar-17 18:36
Member 109051932-Mar-17 18:36 
QuestionSampling/buffering issue Pin
Member 1254606925-May-16 7:12
Member 1254606925-May-16 7:12 
QuestionNo input device detected Pin
Member 115043816-Nov-15 6:47
Member 115043816-Nov-15 6:47 
QuestionAbout can't exit the application, I had only disabled this row. Pin
neil23335-Oct-15 15:15
neil23335-Oct-15 15:15 
AnswerRe: About can't exit the application, I had only disabled this row. Pin
Member 120005677-Oct-15 23:20
Member 120005677-Oct-15 23:20 
QuestionFrequency-range Pin
Member 120005675-Oct-15 0:02
Member 120005675-Oct-15 0:02 
QuestionThanks Pin
se5a25-Jun-15 14:52
se5a25-Jun-15 14:52 
Questionfrequency Pin
Member 1067234319-Jun-15 10:51
Member 1067234319-Jun-15 10:51 
AnswerRe: frequency Pin
Member 120005675-Oct-15 0:03
Member 120005675-Oct-15 0:03 
QuestionShutdown and stereo/mono fixes Pin
chronogeo19-Oct-14 22:27
chronogeo19-Oct-14 22:27 
AnswerRe: Shutdown and stereo/mono fixes Pin
chronogeo19-Oct-14 22:28
chronogeo19-Oct-14 22:28 
GeneralRe: Shutdown and stereo/mono fixes Pin
chronogeo19-Oct-14 22:29
chronogeo19-Oct-14 22:29 
GeneralRe: Shutdown and stereo/mono fixes Pin
chronogeo19-Oct-14 22:31
chronogeo19-Oct-14 22:31 
QuestionUI Thread locks up on close Pin
Member 1107721311-Sep-14 22:07
Member 1107721311-Sep-14 22:07 
QuestionHelp please: Nasalance ratio Pin
alijahan25-Jun-14 6:16
alijahan25-Jun-14 6:16 
GeneralThanks a lot! Pin
lopopoo21-Nov-13 4:25
lopopoo21-Nov-13 4:25 
QuestionExcellent article; quick question: would it be possible to "listen" to speaker output? Pin
Member 1029319528-Sep-13 7:17
Member 1029319528-Sep-13 7:17 
QuestionDelay/Latency Pin
hieronymusde13-Aug-13 11:21
hieronymusde13-Aug-13 11:21 
GeneralMy vote of 5 Pin
hieronymusde13-Aug-13 10:04
hieronymusde13-Aug-13 10:04 
QuestionHelp for operation on a modulated signal Pin
galbandrea14-Apr-13 22:13
galbandrea14-Apr-13 22:13 
Bug"В экземпляре объекта не задана ссылка на объект." Pin
Member 99607234-Apr-13 1:54
Member 99607234-Apr-13 1:54 
Questionis there a way to select the iinput device (directx name ?) Pin
patrick zuili17-Mar-13 18:34
patrick zuili17-Mar-13 18:34 
Generalamazing one Pin
Member 810718412-Jan-13 5:07
Member 810718412-Jan-13 5:07 
GeneralMy vote of 5 Pin
javcastaalm23-Nov-12 9:08
javcastaalm23-Nov-12 9:08 

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