Python voice modem

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Python voice modem

In one of my current prototype projects I need to encode voice into binary data and then later transfer it through a voice channel. This forced me to push my limits and learn new things which I will describe here.

This post will explain technologies I use, rationale behind them, and give basic advice on how to use them. First I will describe basic theory around modulation and demodulation, then I will describe how to combine Cython and profiling to build a flexible and efficient Python application. In the last section I will talk about pulseaudio and how it allows me to perform user testing without using an external device.

The module that I am building encodes and decodes voice. The encoder has one input: a continuous stream of voice represented by audio samples.

On the output it plays audio that is transmitted by an independent voice communicator. The decoder does the reverse. What makes this task non-trivial is that in the middle the voice is encoded, producing a seemingly random bytestring. This task includes a few challenges:. The sound that we hear is a result of a mechanical wave of pressure and displacement propagating through air.

python voice modem

As such we can represent any sound as a wave. Wave being a continuous signal needs to be discretized to be representable in computer memory and there are two ways to go about it. First we can represent a wave as a sum of its fundamental frequencies. It is a mathematical fact that:. Every continuous function on closed interval can be represented as a potentially infinite sum of basic frequencies, that is:.

We might keep a table of coefficients for all audible frequencies. Humans can hear up to 20kHz, so the size of this table goes up to thousand for each time frame. This representation may allow for easier reproduction of signal through mechanical means combine all those fundamental frequencies and you are donebut is impractical. The second raw representation uses samples of the wave taken at specified intervals. For example a typical. The frequency of sampling is called a sampling rate.

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The sampling rate used in telephony is Hz. The reasoning behind the value of the sampling rate will be explained later. Both representations are equivalent in the sense that one can transform from one to the other. From fundamental frequencies we can produce sampling by simply calculating wave values at given points.

To get the other way around we need to use the discrete Fourier transform. Fourier transform is a general mathematical tool which transform a wave function into a function of fundamental frequencies. That is the resulting function maps each of its argument to its power inside the argument. The discrete version of the Fourier transform maps list of samples of the wave to values of fundamental frequencies of the wave that generated them.

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The formula looks as follows:. Where are samples and is a complex number representing fundamental coefficients in the form of: if and. Note that I am using as the upper limit of the sum instead of often seen. Naively calculating the DFT takes time. Fortunately there exists a fast Fourier transform algorithm which takes.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.

If nothing happens, download GitHub Desktop and try again. If nothing happens, download Xcode and try again. If nothing happens, download the GitHub extension for Visual Studio and try again. It also includes a couple of useful commandline utilities for interacting with a GSM modem. Download a python-gsmmodem-new archive from PyPIextract it and install the package with command:.

Unit test code coverage information may be generated by using coverage. You can execute it directly from setup.

13. Speech Recognition with Convolutional Neural Networks in Keras/TensorFlow (2019)

This package contains Sphinx -based documentation. To manually build or test the documentation locally, do the following:. For true isolation, you may wish to run the above commands within a virtualenvwhich will help you manage this development installation.

Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Sign up. Python Branch: master. Find file. Sign in Sign up. Go back. Launching Xcode If nothing happens, download Xcode and try again. This branch is 8 commits behind babca:master.

Pull request Compare. Latest commit Fetching latest commit…. It features command completion, built-in help for many AT commands, history, context-aware prompt, etc. Can also be used to provide debug information used for development of python-gsmmodem. Requirements Python 2. Manual installation of the latest "stable" release from PyPI Download a python-gsmmodem-new archive from PyPIextract it and install the package with command: python setup.Do you have a GitHub project?

Now you can sync your releases automatically with SourceForge and take advantage of both platforms. Program to block junk calls. Connects to a modem and listens for a caller ID.

It then reads strings from a blacklist file and scans them against the caller ID. On a match, it sends commands to the modem that terminate the call. Mailing lists for Codec 2 and Oslec open source line echo canceller. Its used with analog fm ham tranceivers to transmit digital voice D-Star and more or data. What is t38modem? From IP network view point it's a H. From your view point it's a gateway between an application and IP network. Works with HylaFAX. This application has been made to enable user to: 1.

Transfer files through the phone line 2. Make a phone call through the modem if the modem supported voice 3. Make a phone operations remotely through the network. This is a manager of voice messages received by voice modem using vgetty. You can easy play messages and delete it. VoiFax is thinking for use in the small businness as in the enterprises. It is fully compatible with vgetty scripts and manage via efax modem fax 1.

Komms will be a complete communications package for Linux based machines. Using a Voice Modem as the base of an IVR system, it has been running 24x7 since Nov at my home handling phone calls and emailing the results. Call waiting detector for Linux. Allows to detect and answer incoming voice calls when connected via modem. Fax software that supports class1. With USR modemvoice mode is supported. Since this software is implemented as an extension of ruby scripting language, you can easily create your own app.

Will be completely modularised, allowing differing daemons to handle fax, data and voice calls. Telephone Control Daemon allows a user to dial a system and perform some predefined commands.

It is useful for systems that only have a temporary Internet connecti. This is an application inspired by Rapidcom Voice for Windows. It is an app that lets you use a voice modem as an answering machine,and a Fax. I also plan to let it act as a dialup shell account.

The homepage is now active. A windows program that manages scheduled PA announcements and "bells" using a voice modem.This first tutorial shows how to make a call to an arbitrary destination using the Voip Library.

To make a call, you have to perform the following steps, each of them explained in the next sections.

python voice modem

Note that this example, to work, requires a Sip Server e. For getting instructions about the Asterisk configuration, click here. You can choose an arbitrary name for this method, but it must contain the following 3 arguments: 1.

At this point, you are ready to initialize the library passing the dictionary and the callback method defined above:. The example above assumes that you have a Sip Server e. Note that, so far, no connection to the Sip Server has been established yet. Now, you are ready to register the user to the sip server in this example, we are registering a user called ste with the password ste. We assume that the Sip Server knows this user and is able to accept the registration request from it.

In particular, this method is called as soon as a registration request is sent with a VoipEvent. In case of successfull registration, you can dial an extension or call an arbitrary Sip User in the following way:. Note that, when the user hangs up the callthe callback method is called again with the event VoipEvent. Most Voip API latest. At this point, you have to implement a callback method that will be.Noticeably though, for the straightforward and simple use case of just calling an individual, the costs can really start to add up.

This is something like pennies per minute, and is indeed cheap, but it turns out that writing your own VOIP client is even cheaper and otherwise really fun to work on and figure out. I assumed that data was encoded on the fly one small packet at a time and streamed over the wire, but it actually works by taking very small samples which are then very large by computer standardsand encoding each sample individually. The associated lag is imperceptible to a human. A short history of open source codecs before you start searching all over the internets: Speex used to run the open source game of audio codecs, but then Skype opensourced Silk which outperformed Speex in terms of the audio codec.

Silk is integrated into Opus which is an all encompassing-library for various codecs based on the input audio. I found a project set up for Opus here on GitHubwhich was all I ended up needing to get up and running. Opus is otherwise well documented and you just need to patiently read through the docs to get something up and working.

For Voice Over IP in particular, if you understood how things worked it was incredibly easy to actually create the point to point connection thanks to PubNub. With PubNub, you can get a sample project up and running in less than 10 minutes for extremely cheap. This is a difference by a factor of 10 to 1! At scale, this can be a huge money saver. This also leaves plenty of room to increase the same rate if we wanted and still maintain really cheap prices. Conceptually the above descriptions can be done any way, but I used the Swift programming language which turns out to be really awesome even beyond the context of user interface heavy applications.

C code can be interfaced with directly, which was handy for this project, and if you needed the code to run really fast, you could. You can take an array and cast it to a pointer, so you can cast a block of bytes and immediately cast them to another type which was a necessity to transmit an array of PCM values represented as floats.

I used memcpy once more, wielding one of the modern marvels of human techmology. Multi-threading is a forefront consideration of the language, and immutably helps in that respect as well. But I digress. The in between was the above described and done quickly with a low level compiled languageand by using Swift it was simple to interface with a C library.

In the age of ubiquitous telephony, the application I wrote itself is underwhelming from a physical standpoint.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

The dark mode beta is finally here.

python-gsmmodem-new 0.12

Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I want to if know is there any way to call to a number and send some digits to it after picking up the phone using a dial-up modem in Python?

I already did a Google search and found the PyModem library, but it is written for Linux and for GSM modems, while I want its counterpart for Windows and for dial-up modems.

I also found some related topics here and here that containsome piece of code for working with modems using the serial library, but I don't understand why a modem is recognized as a serial device! Maybe in the past, dial-up modems used COM port to communicate with computers, but my modem is connected to the main board using a PCI slot. So, How can I communicate with a dial-up modem d-link isfor example using python in windows? If you look at the description of the d-link IS, you'll see mentioned that it is a software modem.

So most if not all of the functionality is in the driver, not in the hardware. The Linux driver seems to emulate a serial port because that is the standard way to talk to modems on UNIX. Apparently the windows driver doesn't. Looking through the dll files in the windows driverthere is a ModemOpen function defined in MdmXSdk. You could call that using ctypes. Or you could try using the telephony api. Learn more.

Communicating with dial-up modems Ask Question. Asked 4 years, 11 months ago. Active 4 years, 11 months ago. Viewed 1k times. Regarding COM ports, a lot of device drivers emulate a COM port, even if they're physically connected some other way, because it's a simple interface for the client software to talk to.We are always striving to improve our documentation quality, and your feedback is valuable to us.

How could this documentation serve you better? In this guide, we'll show you how to use Programmable Voice to make outbound phone calls from your Python applications.

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It's pretty easy - all you'll need is the Twilio Python SDKa voice-capable Twilio phone number, your account credentials and five minutes to have a boatload of fun at your keyboard. Let's get started!

Lessons in writing and testing an audio modem in Python

In the Twilio consolesearch for and purchase an available phone number capable of making outbound calls. You'll use this phone number as the "From" phone number when you initiate an outbound call. First, you'll need to get your Twilio account credentials. They consist of your AccountSid and your Auth Token. They can be found on the home page of the console. TwiML is easier shown than explained. Here's some TwiML you might use to respond to an incoming phone call:.

Of course, the TwiML you use to make the outbound call doesn't need to be a static file like in this example.

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Server-side code that you control can dynamically render TwiML to use for the outbound call. Check out our inbound call guide to see an example of a Python server which generates TwiML. Great work! In a few lines of code, you've placed an outbound phone call from your Python code. If you're using Programmable Voice with Python, you might enjoy these other guides as well. We all do sometimes; code is hard. Get help now from our support teamor lean on the wisdom of the crowd browsing the Twilio tag on Stack Overflow.

python voice modem

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