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Sound Activated Recorder with Spectrogram in C#

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4.92/5 (54 votes)
27 Jan 2008GPL3 399.6K   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)


Written By
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Comments and Discussions

 
QuestionHow to reduce the noise? Pin
GeoNav31-Oct-09 1:55
GeoNav31-Oct-09 1:55 
Generallineout audio Pin
GeoNav28-Oct-09 23:10
GeoNav28-Oct-09 23:10 
QuestionChange Source to wav file Pin
GeoNav21-Oct-09 21:36
GeoNav21-Oct-09 21:36 
AnswerRe: Change Source to wav file Pin
Jeff Morton22-Oct-09 11:23
Jeff Morton22-Oct-09 11:23 
GeneralRe: Change Source to wav file Pin
GeoNav26-Oct-09 18:35
GeoNav26-Oct-09 18:35 
GeneralRe: Change Source to wav file Pin
afmf3-Nov-09 5:38
afmf3-Nov-09 5:38 
AnswerRe: Change Source to wav file Pin
ravitzur18-Dec-10 23:07
ravitzur18-Dec-10 23:07 
GeneralError in Program Pin
Viktor Signaievskyi20-Oct-09 11:04
Viktor Signaievskyi20-Oct-09 11:04 
GeneralRe: Error in Program Pin
Jeff Morton22-Oct-09 11:23
Jeff Morton22-Oct-09 11:23 
GeneralRe: Error in Program Pin
Viktor Signaievskyi24-Oct-09 0:52
Viktor Signaievskyi24-Oct-09 0:52 
QuestionCan't run the program in Vista 64bit Pin
Yasir Salih Osman7-Aug-09 22:36
Yasir Salih Osman7-Aug-09 22:36 
AnswerRe: Can't run the program in Vista 64bit Pin
Fullmetal9901211-Sep-09 7:20
Fullmetal9901211-Sep-09 7:20 
AnswerRe: Can't run the program in Vista 64bit Pin
Rahdu18-Oct-10 22:09
Rahdu18-Oct-10 22:09 
AnswerRe: Can't run the program in Vista 64bit Pin
Member 320938312-Apr-11 12:10
Member 320938312-Apr-11 12:10 
AnswerRe: Can't run the program in Vista 64bit Pin
Rebmem1529-Sep-11 18:33
Rebmem1529-Sep-11 18:33 
Questionhow can i do it reverse? [modified] Pin
mojimoj2-Aug-09 21:05
mojimoj2-Aug-09 21:05 
I have spectrum signal and i want to play it's sound,
how can i do it????

modified on Monday, August 3, 2009 3:33 AM

GeneralExcellent piece of work Jeff Pin
maxima1204-Jul-09 12:17
maxima1204-Jul-09 12:17 
GeneralRe: Excellent piece of work Jeff Pin
Jeff Morton5-Jul-09 5:46
Jeff Morton5-Jul-09 5:46 
GeneralThrows exception when using Freq &lt; 11025 Hz Pin
JoanComasFdz10-Jun-09 7:07
JoanComasFdz10-Jun-09 7:07 
QuestionHow do I get it to work? Pin
Maiden Computer Company22-Apr-09 10:48
Maiden Computer Company22-Apr-09 10:48 
AnswerRe: How do I get it to work? Pin
Jeff Morton22-Apr-09 10:51
Jeff Morton22-Apr-09 10:51 
QuestionError in Frequency domain? Pin
Elysium8-Mar-09 11:17
Elysium8-Mar-09 11:17 
AnswerRe: Error in Frequency domain? Pin
Jeff Morton8-Mar-09 11:41
Jeff Morton8-Mar-09 11:41 
GeneralRe: Error in Frequency domain? Pin
Elysium8-Mar-09 22:02
Elysium8-Mar-09 22:02 
QuestionQuestion on how to get the frequencies Pin
kyanmark_johnwill2-Mar-09 13:52
kyanmark_johnwill2-Mar-09 13:52 

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