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Dialogic® DM3 and JCT Media Boards

Single-Frequency User-Defined Tones not Detected


Summary
This technical note discusses why using two tone definitions may resolve the issue of single-frequency tones not being properly detected.

Symptom:
Some user-defined single frequency tones are not properly detected when defined using these functions: dx_bldst() or dx_bldstcad().

Reason for the problem:
On Dialogic® boards, all tones are detected using a template that provides two frequencies. When dx_bldst*() is used to define a tone, the second frequency is automatically defined as 0. Generally, when a tone has only a single frequency, the second frequency is 0, so the tone is detected properly.

Sometimes, however, a single-frequency tone is detected as having two frequencies that are very close to each other. Since the frequencies are both detected, and one is not 0, the definition given in dx_bldst*(), is not met.

For example, if a tone with a frequency of 550Hz, an ontime of 600 +/- 300ms, an offtime of 200 +/- 50ms and a repitition count of 3 is defined using dx_bldstcad(), the application code might look like this:

dx_bldstcad( TID_101, 550, 50, 60, 30, 20, 5, 3 )

This would be passed to the library under the hood via function dx_blddtcad() like this:

dx_blddtcad( TID_101, 550, 50, 0, 0, 60, 30, 20, 5, 3 )

 If a tone arrives that is detected as having two frequencies at 530Hz and 560Hz, this would not be detected even though both frequencies fall into the range of the single frequency definition.


Fix / Solution:
For each single-frequency tone, use two calls to dx_blddtcad(). In one definition, make frequency 2 equal to 0. In the second definition, make frequency 2 equal frequency 1. From the example above, make the following two definitions:

dx_blddtcad( TID_101, 550, 50, 0, 0, 60, 30, 20, 5, 3 )
dx_blddtcad( TID_102, 550, 50, 550, 50, 60, 30, 20, 5, 3 )

If the tone has no cadence (for example, a 550Hz tone with an ontime of at least 500ms), the definitions should look like this:

dx_blddtcad(tid_101, 550, 50, 0, 0, 25, -25, 0, 0, 0)
dx_blddtcad(tid_102, 550, 50, 550, 50, 25, -25, 0, 0, 0) 

where on time = 1/2 tone on time and on time deviation = -1/2 tone on time

Product List
Dialogic® DM/IP Boards
Dialogic® JCT Media Boards
Dialogic® Host Media Processing Software Release 3.0 for Windows®
Dialogic® Host Media Processing Software Release 2.0 for Windows®
Dialogic® Host Media Processing Software Release 1.5 for Linux

Related Documentation
Reasons for using dx_blddtcad() for all Tone Defines





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