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Text File | 1995-11-27 | 14.0 KB | 332 lines

╔═══════════════════════════════════════════════════╗ ║ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ║ ║ ▒ ▒ ║ ║ ▒ DTMF Real-Time Decoder -- 486 DEMO Version ▒ ║ ║ ▒ ▒ ║ ║ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ ║ ║ ║ ║───────────────────────────────────────────────────║ ║ Shima-nized Advanced Utilities - J.M. Shima ║ ║ Copyright (c) 1994-95 by James Shima ║ ║ All Rights Reserved ║ ║ ║ ╚═══════════════════════════════════════════════════╝ ▐▐▐▐ R E F E R E N C E M A N U A L ▐▐▐▐ » Type DTMF486D at the DOS prompt for a summary of options « INTRODUCTION ▀▀▀▀▀▀▀▀▀▀▀▀ * This program functions as a real-time DTMF decoder. One application where DTMF tones are used is in the standard American telephone dialing system. The standard DTMF tones represent the numbers 1,2,3,4,5,6,7, 8,9,0,*,# on a standard keypad interface. The four reserved DTMF tones representing A,B,C,D are supported in the REGISTERED version. * This program is capable of decoding DTMF tones from a Soundblaster Version 1.0 - 2.0, Soundblaster Pro, or TRUE Soundblaster compatible (16-bit or 8-bit) sound card in real-time. Soundblaster 16 support has been reported to work but is fully untested at this point. * This 486 version is geared toward persons with a 486DX PC or better. This version can be used by slower machines, but results will be error prone due to the non real-time processing. * If your PC DOES NOT perform equivalent to a 486DX-25 or better, a quasi real-time switch is supported. However, due to the nature of real-time processing, this means data will be lost and results may vary from system to system. * The Soundblaster or compatible sound card MUST be connected to port address 220h and using DMA 1 (the factory settings). * The input to the Soundblaster mic or line input can originate from any external communication device that supplies DTMF tones to the sound card. * This program accepts COMMAND-LINE ARGUMENTS that are passed to the DTMF decoder. * For a list of the arguments, type DTMF486D at the DOS prompt. * The DEMO only decodes a maximum of 5 numbers. Interested persons can receive the REGISTERED version with no limitations. SOFTWARE LICENSE ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀ The 486 DEMO version of the DTMF real-time decoder is shareware, and is free for personal use only. This is true as long as the DEMO is not alterted in any fashion. Registered users will receive the REGISTERED version of the DTMF decoder and will receive documentation stating such. The author offers no warranties on this program. This program is provided as is. Use this program at your own risk. I assume no responsibility in your actions while you are using this program. The author is not liable for any damage caused to your computer while you are using this program. Using the program is your compliance to this statement and the license. COMMAND-LINE ARGUMENT SCREEN ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀ The program argument screen should look as follows: Real-Time Dual-Tone Multi-Frequency Decoder, 486 DEMO Version Shima-nized Advanced Utilities (c) 1994-95 - J.M. Shima USAGE: DTMF486D <sample_rate> switches:[ <-t>number <-r>] Notes: <sample_rate> = rate of incoming samples in Hz. The range is 4000 < fs < 12000 for DTMF decoding. The RECOMMENDED value is 4000 Hz for real-time decoding. ** Sound card must be Soundblaster 1.0 - 2.0, Pro, or Soundblaster ** compatible connected to port 220h using DMA 1 (The factory settings). Switches: -t = Defines the S/N threshold value (in dB) that DTMF tones must surpass for proper detection. The threshold S/N value can be any real, non-negative number. DEFAULT value is 20 dB. -r = Enable real-time mode. Use this for a 486DX-25 machine or up. Otherwise, use quasi real-time mode which is probable to give inconsistent results. Real-time mode is OFF by DEFAULT. EXPLANATION OF COMMAND-LINE ARGUMENTS ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀ <sample_rate> --> Input sample rate. Must be in the range of 4000 to 12000 Hertz (Hz). For DTMF detection, it is HIGHLY RECOMMENDED THAT YOU USE 4000 Hz for real-time processing. However, testing indicated that a 486DX-66 could perform real time processing with a 8000 Hz sample rate. Switches: ════════ -t<number> --> The threshold that the DTMF tones must exceed over the noise floor for detection (in dB). Typically, strong DTMF tones will be 20-40 dB stronger than the noise in the signal. However, noisy signals lower this signal-to-noise (S/N) ratio. The threshold parameter allows the user to set the S/N threshold for detection of noisier or corrupted DTMF tones. * NOTE: If nothing is entered, then the DEFAULT S/N threshold value is 20dB, which is a figure of merit for normal tones. One must realize that dB is a logarithmic scale of signal gain through the equation: dB = 20 * log(signal gain). Thus, a large signal gain represents a small increase in the dB number (i.e. 40dB is a 100x signal gain, while 20dB is a 10x signal gain). -r --> Enables TRUE real-time processing mode. Include this switch if your system is capable of handling the flow rate of data. Rule of thumb: A 486DX-33 can probably handle real-time. ** NOTE: Results will VARY from system to system. By default, a quasi real-time process is included for slower machines. Obviously, this means data will be lost due to computational overhead, put I have tried to STRATEGICALLY MINIMIZE the effects of this. EXAMPLES OF RUNNING DTMF486D ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀ * Program start: Run the program by typing the executable name. * Program end: The program ENDS when ANY key is hit during decoding! DTMF486D 4000 --> Input sample rate is 4000 Hz. Quasi real-time mode is enabled by default. Input S/N threshold defaults to 20dB. DTMF486D 4000 -t25 --> Input sample rate is 4000 Hz. The input S/N threshold is set to 25dB. Quasi real-time mode is enabled. DTMF486D 4000 -r -t15 --> Input sample rate is 4000 Hz. The S/N threshold is set to 15dB. Real-time mode for fast machines is enabled. IMPORTANT NOTES ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀ Since this is a real-time piece of software, certain rules must be followed for proper use. Sampling rate: Increasing the sampling rate means that samples are ready faster. Thus, the computer has less time to do what is has to before it has to fetch more samples. So, one must make the sample rate as low as it can go and still represent the maximum frequency in the signal. For DTMF tones, this minimum sampling rate is 4000 Hz, (due to Nyquist theorem). IT BEHOOVES YOU to use this rate. Sampling at a rate higher than necessary gains you nothing, but INCREASES your computational overhead. For real- time operation, make your sampling rate as low as you can without violating Nyquist theorem (2x the maximum freq. in the signal). So, for all practical purposes, use 4000 Hz as your sampling rate. Real-time processing: If your system cannot handle real-time processing, that means data will be lost. While your system is processing the old data, it doesn't have time to retrieve the new data coming in. This new data is discarded and the computer picks up fresh data when it's done with its current task. Thus, results are inconsistent when real-time processing cannot be done. The probability of detecting a given tone depends on where your computer is in its processing stage. You can see that its nearly impossible to debug whether or not real-time processing is happening or not. On top of this, your CPU takes care of many other housekeeping tasks. Therefore, I have deemed "real-time" on the fact that a DTMF tone does not go undetected as given in the DTMF standards. Closely spaced tones will be detected in real-time if your system can run the code in real time. However, you can also decode all DTMF tones if there is enough time between tones and your computer works fast enough so to extract some data from each tone. In this case, the decoder is not working in real time but is able to extract data since a tone exists for a longer amount of time than it takes to perform a detection. In other words, longer DTMF tones are better detected in quasi real-time mode. DTMF tones invoked by humans are very long compared to the time it takes your computer to detect them, so in quasi-real time mode you should be able to get good results. This is why probability governs the detection process in the quasi real-time case. Noisy DTMF tones are also error ridden since the processing window is so small no noise immunity algorithm can be implemented. Note that non-pure tones may not be detected properly! INCLUDED FILES ▀▀▀▀▀▀▀▀▀▀▀▀▀▀ DTMF486D.EXE --> DTMF real-time decoder, DEMO version. DTMF486D.DOC --> This file. REGISTER.DOC --> Registration form. REGISTRATION ▀▀▀▀▀▀▀▀▀▀▀▀ ** For registration, please fill out REGISTER.DOC and see the DEMO screen. Specify media dispersement. The REGISTERED version of this program allows unlimited decoding of numbers, and offers other features including: 1) Automatic logging of the resulting decoded numbers to a log file. The session is also time and date stamped. 2) Time monitoring switch. Allows deciphering of incoming streams of numbers if tone activity is not detected for a set number of seconds. 3) Supports the extended DTMF tones A,B,C,D. 4) REGISTERED users will also receive a DTMF generator program. This is a DTMF tone generator which allows you to create any DTMF sequence you wish. The program allows you to specify a DTMF number sequence, the sampling rate, and how long you want the pulses to be (in samples). TESTING ▀▀▀▀▀▀▀ I have thoroughly tested this code and I am not responsible for any mishaps that may happen when run on your computer. SOUND CARDS TESTED: Aztec Sound Galaxy 16 bit Sound Blaster 8 bit Sound Blaster ASP 16 Generic SB fully compatible 16 bit Sound Blaster 16 VE * * Some problems with the SB 16 VE have been reported and verified. Mic and line inputs for the SB 16 VE gave spurious results. No explanation for this hardware problem has been determined. TESTING PLATFORMS: 1) The code was tested on an IBM compatible 25MHz 486DX Cyrix upgrade PC with a Soundblaster Version 1.5 sound card running DOS 5.0. Tones were recorded onto a cassette tape and played into a microphone which was connected to the mic input of the Soundblaster card. It was able to run in quasi real-time mode with a 4000 Hz sample rate and decoded numbers with approximately 90% accuracy. Real-time mode was unachievable but gave similar results. Using this test vector data, normal dialing was decoded 95% of the time. Burst dialing was decoded 95% of the time. Noisy tones gave inconsistent results. ** NOTE: All captured numbers were correctly decoded, the errors stemmed from the fact that real-time decoding was not possible! 2) The code was also tested on a 486DX2-66 with an Aztec Sound Galaxy 16-bit Soundblaster compatible sound card. The code was ABLE to run in REAL-TIME on a 486DX2-66 with sample rates of 4000 Hz and 8000 Hz!! Using recorded test vector data, DTMF decoding was 100% accurate! Normal and burst dialing were decoded 100% of the time. Again, noisy tones were inconsistent due to the streamlined algorithm. Every action has been taken to ensure an error-free program. Note, incompatibilities may stem from hardware deviations. For optimal performance, DO NOT launch this program while running under Microsoft Windows. For more information, EMAIL: shima@cyberramp.net US MAIL: J.M. Shima 18909 Lloyd Circle Apt. 1232 Dallas, TX 75252 TRADEMARKS ▀▀▀▀▀▀▀▀▀▀ Soundblaster is a trademark of Creative Lab's Inc. Microsoft Windows and DOS is a trademark of Microsoft.