[Asterisk-Dev] zt_tone_def explanation

[Karl Brose]

No, not DTMF,  it is used to generate the tone indications (playtones) 
which are either pure frequencies, combinations of two,
or modulated frequencies, see also  zonedata.c and indications.conf


el Flynn wrote:

> hi there,
>
> in the zaptel.h file, i found the following bit of code:
>
>     Calculate the next 6 factors using the following equations:
>     l = <level in dbm>, f1 = <freq1>, f2 = <freq2>
>     gain = pow(10.0, (l - 3.14) / 20.0) * 65536.0 / 2.0;
>
>     // Frequency factor 1
>     fac_1 = 2.0 * cos(2.0 * M_PI * (f1/8000.0)) * 32768.0;
>     // Last previous two samples
>     init_v2_1 = sin(-4.0 * M_PI * (f1/8000.0)) * gain;
>     init_v3_1 = sin(-2.0 * M_PI * (f1/8000.0)) * gain;
>
>     // Frequency factor 2
>     fac_2 = 2.0 * cos(2.0 * M_PI * (f2/8000.0)) * 32768.0;
>     // Last previous two samples
>     init_v2_2 = sin(-4.0 * M_PI * (f2/8000.0)) * gain;
>     init_v3_2 = sin(-2.0 * M_PI * (f2/8000.0)) * gain;
>
> if i'm not mistaken, this has something to do with generating DTMF 
> tones. can someone give more insight on what the init_v2_1, init_v3_1, 
> init_v2_2, init_v3_2 variables are used for?
>
> and also perhaps what this bit of code does? I think it's used in 
> tonezone.c
>
> thanks a bunch.
>
> Flynn
>
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