Programming Forums > Application Development > C

timrochester · Sep 7th, 2005, 4:41 PM

I am quite new to C programming, but have grasped the concept quite well and am interested in writing a function that can be used to run an audio level meter.

This function should return a number depending on the loudness of the input comming from the microphone on a laptop.

I scoured the internet, but cannot find a way of retrieving sound from the input for processing, i can record it but that doesnt help

Any ideas would be appreciated!

Thank you

tempest · Sep 7th, 2005, 7:45 PM

If you can record it, then it becomes a matter of analyzing the data you're getting from the mic

iignotus · Sep 7th, 2005, 9:05 PM

Sounds like you need to investigate the Fourier Transform. It takes audio data and represents it as Hertz and Decibels.
http://en.wikipedia.org/wiki/Fast_Fourier_transform
http://mathworld.wolfram.com/FastFourierTransform.html
http://www.fftw.org/
http://astronomy.swin.edu.au/~pbourke/other/dft/
http://homepages.inf.ed.ac.uk/rbf/CV...LL/node20.html
http://en.wikipedia.org/wiki/Discrete_Fourier_transform

DaWei · Sep 7th, 2005, 9:22 PM

When you say you can record it, does that mean with your own software, or just with one of your existing apps?

timrochester · Sep 10th, 2005, 6:13 PM

I apologise for it taking ages to reply to this, i thought i subscribed to this so i get e-mails when new posts are made

I have found bits and peices that can record the microphone input to a wav file, but not tried writing a program based on that information, as i have no idea how to intercept, or read back the information recorded.

I have read the fourier pages and it looks like its helpful, what i need now is some help writing the code to get the sample voltages from the microphone to variables in a program. I dont even know which API to use... Or if there is an alternative

Sep 7th, 2005, 4:41 PM	#1
timrochester Newbie Join Date: Sep 2005 Posts: 2 Rep Power: 0	Audio Level I am quite new to C programming, but have grasped the concept quite well and am interested in writing a function that can be used to run an audio level meter. This function should return a number depending on the loudness of the input comming from the microphone on a laptop. I scoured the internet, but cannot find a way of retrieving sound from the input for processing, i can record it but that doesnt help Any ideas would be appreciated! Thank you

Sep 7th, 2005, 7:45 PM	#2
tempest Programming Guru Join Date: Oct 2004 Posts: 1,041 Rep Power: 5	If you can record it, then it becomes a matter of analyzing the data you're getting from the mic __________________

Sep 7th, 2005, 9:05 PM	#3
iignotus Professional Programmer Join Date: Apr 2005 Location: Nowhere Special Posts: 466 Rep Power: 4	Sounds like you need to investigate the Fourier Transform. It takes audio data and represents it as Hertz and Decibels. http://en.wikipedia.org/wiki/Fast_Fourier_transform http://mathworld.wolfram.com/FastFourierTransform.html http://www.fftw.org/ http://astronomy.swin.edu.au/~pbourke/other/dft/ http://homepages.inf.ed.ac.uk/rbf/CV...LL/node20.html http://en.wikipedia.org/wiki/Discrete_Fourier_transform __________________ (Toggle Plain Text) % rc4 hexkey < input > output #define S ,t=s[i],s[i]=s[j],s[j]=t /* rc4 hexkey <file / unsigned char k[256],s[256],i,j,t;main(c,v,e)charv;{++v;while(++i)s[ i]=i;for(c=0;(v)++;k[c++]=e)sscanf((v)++-1,"%2x",&e);while(j+=s[i] +k[i%c]S,++i);for(j=0;c=~getchar();putchar(~c^s[t+=s[i]]))j+=s[++i]S;}

Sep 7th, 2005, 9:22 PM	#4
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	When you say you can record it, does that mean with your own software, or just with one of your existing apps? __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

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Sep 10th, 2005, 6:13 PM	#5
timrochester Newbie Join Date: Sep 2005 Posts: 2 Rep Power: 0	I apologise for it taking ages to reply to this, i thought i subscribed to this so i get e-mails when new posts are made I have found bits and peices that can record the microphone input to a wav file, but not tried writing a program based on that information, as i have no idea how to intercept, or read back the information recorded. I have read the fourier pages and it looks like its helpful, what i need now is some help writing the code to get the sample voltages from the microphone to variables in a program. I dont even know which API to use... Or if there is an alternative

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Programming Forums > Application Development > C

Audio Level