Static DSP Operations
Scripted DSP commands provide the ability to specify a sequence of digital signal processing steps to be performed on incoming and/or outgoing timeslots. The WCS DSP Operation module allows real-time as well as offline testing using DSP commands to perform functions such as Amplification/Attenuation, Delay, Filter, File Tx/Rx, Logical operations, Echo Cancel, and so on.
Complex echo paths and complex block diagram operations can be easily simulated using the following functions: sum, invert, filter, delay, amplify, attenuate, bxor, bor, brev, bnot, band, infile, outfile, white noise, tone, dual tone, phase shift, dtmf digits, mf digits, mfcr2 digits, power monitor, signaling bits monitor, const, bytes, and many other operators.
Example processing structures that can be accomplished are shown below:
In Figure 1, digitally synthesized sources (generators) of tone, noise, DTMF digits, MF digits, and dualtone are summed and transmitted into timeslot 5.
In Figure 2, multiple dualtone generators with possibly different parameters are summed and transmitted into timeslot 23.
In Figure 4, receive timeslot 5 is summed with delayed and attenuated versions of itself and transmitted back into timeslot 5. Such a structure may be useful in modeling echo paths and testing echo cancellers.
In Figure 5, a more complex structure for echo path modeling is shown. Three parallel echo paths are summed with a digitally synthesized tone and noise and a PCM file.
DSP Static Operations using C++ client
Transmit filtered tones and white noise
This script transmits two tones at different frequencies along with white noise and DTMF digits. The output is obtained through a filter.
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Adding speech and noise to the receive data
This script transmits the amplified speech file with white noise and the data received on a particular timeslot.
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Adding noise and phase shift tone to the speech data
This script transmits an amplified speech file with a continuously phase shifted tone combined with a white noise through a filter.
Download scripts for Adding noise and phase shift tone to the speech data.
Testing Arithmetical Functions on Incoming Bit Stream
This script performs various types of arithmetical functions on the incoming bit stream.
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Double talk simulation for echo canceller testing
This script emulates the far end and near end call for echo canceller testing.
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Tone Decoder and ADSI decoder
The DSP commands also allow to monitor Tones, Digits, and other traffic generated using above static DSP operations. Additionaly, with the new Tone Decoder and ADSI decoder DSP commands, it is possible to detect Caller IDs including CID, CIDCW (Call Waiting), VMWI (Visual Message Waiting Indicator) signal types. Supported encoding formats include alaw, mulaw, pcm16, pcm14, and pcm13.
In the above screenshot the sample .ula file has a pre-recorded caller id information, here decode tones command is used to decode the caller id information and notify as an event. Similarly, decode tones, tone decoder, or adsi decoder commands can also be used to decode CID, CIDCW, and VMWI information.
Download the sample scripts to detect caller id.
Other Sample Scripts
List of some sample DSP scripts using TCL client
- Transmit white noise
- Transmit tone on all timeslots
- Transmit file
- Transmit dual tone
- Transmit Constant and ASCII values
- Transmit phase shift tone
- Transmit DTMF/MF/MFR2B/MFR2F bits
- Delay and attenuate the transmitted tone
- Script to verify boolean expressions
- Script to detect caller ID