Voice over IP

Discussion in 'Java' started by laurascomputer4@googlemail.com, Jan 18, 2008.

  1. Guest

    hi

    as a rookie with java, i would like to ask for some help with starting
    to create a basic java software to allow voice over ip. i understnad
    that layers will have to be used for functionality. and that a
    standard will be needed so that 2 computers can communicate with one
    another.

    However with a project such as this, how would one begin? can anyone
    suggest any helpfull hints or tips?

    thanks.
     
    , Jan 18, 2008
    #1
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  2. wrote:
    > hi
    >
    > as a rookie with java, i would like to ask for some help with starting
    > to create a basic java software to allow voice over ip. i understnad
    > that layers will have to be used for functionality. and that a
    > standard will be needed so that 2 computers can communicate with one
    > another.
    >
    > However with a project such as this, how would one begin? can anyone
    > suggest any helpfull hints or tips?
    >

    You'll probably need three types of program - the VOIP client, some sort
    of directory server and a directory maintenance program, though the last
    might be simply a text editor - so, lets assume it is, and the directory
    is a simple text file with each subscriber's details on a separate line.

    Start by writing the client and directory programs. Concentrate first on
    having the client do a directory lookup and then making a connection to
    a second client. Making them exchange text files in both directions
    simultaneously would be a straight forward initial test and much easier
    to debug. Sending the files line by line is an approximation to sending
    audio packets.

    When that's working reliably you can replace the text exchange with
    audio packets. Hint, look at the RFCs and other relevant standards for
    streaming audio protocols before designing your own - there's no sense
    in repeating work that's been done already.


    --
    martin@ | Martin Gregorie
    gregorie. | Essex, UK
    org |
     
    Martin Gregorie, Jan 18, 2008
    #2
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  3. Guest

    Thanks Martin,


    i dont think i will be creating my own standard but using ones already
    available.

    however on initial testing i was thinking of using the computers IP
    address to make the initial connection, with a number pad designed in
    the GUI, however im unsure how to go about doing so.

    if computers are already connected on a network, picking the IP
    address of one individual computer, then sending information to that
    one only..??
     
    , Jan 18, 2008
    #3
  4. Roedy Green Guest

    On Fri, 18 Jan 2008 01:54:38 -0800 (PST),
    wrote, quoted or indirectly quoted
    someone who said :

    >as a rookie with java, i would like to ask for some help with starting
    >to create a basic java software to allow voice over ip


    You need several pieces.

    1. Something that will capture microphone output in real time.

    2. Something that will play a short sound file in real time, without
    pause between the next.

    3. Something to compress/decompress the voice. It might even pay to
    do FFTs and compress that.

    4. transport layer, most likely UDP Datagrams. If you lose a packet,
    you'd better hear silence than have a echo delay introduced that you
    never make up.

    5. Some sort of server phone book and a scheme to make connections and
    warn subscribers of incoming calls.

    See http://mindprod.com/jgloss/udp.html
    http://mindprod.com/jgloss/jmf.html
    http://mindprod.com/jgloss/fft.html
    http://mindprod.com/jgloss/servletwomb.html
    --
    Roedy Green, Canadian Mind Products
    The Java Glossary, http://mindprod.com
     
    Roedy Green, Jan 18, 2008
    #4
  5. Jeff Higgins Guest

    laurascomputer4 wrote:
    > hi
    >
    > as a rookie with java, i would like to ask for some help with starting
    > to create a basic java software to allow voice over ip. i understnad
    > that layers will have to be used for functionality. and that a
    > standard will be needed so that 2 computers can communicate with one
    > another.
    >
    > However with a project such as this, how would one begin? can anyone
    > suggest any helpfull hints or tips?
    >


    If you are hoping to work from first principles then Martin and Roedy
    have given good starting points. If you just want to get something
    up and running I can suggest an introductory walk through text by
    Cokorda Raka Angga Jananuraga in his PDF booklet titled,
    "Introduction to Telephony Application Development
    Using Asterisk, AsteriskJava, and SIP" (~5M).
    <http://www.geocities.com/rakabali78/booklet1/>

    JH
     
    Jeff Higgins, Jan 19, 2008
    #5
  6. wrote:
    >
    > however on initial testing i was thinking of using the computers IP
    > address to make the initial connection, with a number pad designed in
    > the GUI, however im unsure how to go about doing so.
    >

    You could do that, but why not use the host names? They're easier to
    remember and can simply be input via a JTextField if you want to use a GUI.

    Running the VOIP program in the background as a server and controlling
    it from a command line client ("java voip hostname" makes a call and
    "java voip end" ends it) is simple to do, avoids cluttering your desktop
    with a GUI and the complexity of supporting it. The VOIP program would
    listen on a socket for commands from the command line utility.

    The command line utility can be replaced later with a GUI without
    altering the VOIP program in any way or you can use desktop icons to
    issue the commands via scripts. Most operating systems have utilities
    that can prompt for a string and pass it back to its calling script.


    --
    martin@ | Martin Gregorie
    gregorie. | Essex, UK
    org |
     
    Martin Gregorie, Jan 19, 2008
    #6
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