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how to create wave file of certine frequency for DSP algos.

Anyone can help me in creating a wave file of certine frequency and how to play them in VC++. I have little clue about MMSystem. I need this to implement a DTMF software decoder. And for this first I've to generate sounds of frequency that are DTMF standard than add them up and than decode the pressed buttons.
Thanx in advance.


  • cbodapaticbodapati Posts: 65Member
    >>I need this to implement a DTMF software decoder. And for this first

    can u tell me the DTMF std frequencies.
    do u know IDFT and if so u can calculate the time domain points the desired frequency.


  • mobby_reloadmobby_reload Posts: 51Member
    Hi Srikanth,
    I've generated the samples of the corrosponding signals given as under

    x[n] = sin((2*pi*n*697)/8000) + sin((2*pi*n*1209)/8000);

    here 697 is the low frequency and 1209 high frequency. Whenever you dial from your phone each digit is represented by these corrosponding frequencies. One digit is a sum of it's corrosponding row and col frequency and on the other hand you can find which digit was pressed by checking these frequencies. Now can you plz tell me exactly what kind of frequency selective filter I would implement here to find out the sum is composed of what frequencies. If you give me some mathematical expression than it would be easy for me to implement.
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