Beginner's Guide to Vic

Watching a session advertised in sdr

• Adding vic to your path
  The first thing you need to do is to make sure that the vic binary is in your path.
  - in Unix you can check if vic is in your path, by using the which command (which vic). If this command returns a valid vic executable then vic is in your path. If it does not then you need to edit your path variable and add the directory where you have placed the vic executable to your path.
  - in Windows, the path variable is set in the autoexec.bat file. It is generally recommended in Windows 95 or NT that the vic binary be placed in a directory called C:\MBONE.

• Launching vic from sdr
  If the session was advertised as having video then when you click on the session in sdr you should get a window that lists the various media included in the session and one or more of them should be video. If you click on either the join or the video button then the vic session will pop up with the parameters set appropriately for receiving the advertised session. If vic does not pop up, the first thing to check is that vic is in your path.

• Expanding the thumbnails
  If you are receiving video feeds they will each show up as a little thumbnail sketch with information about the transmitter to the right of the thumbnail. If you would like to see the video in a larger window then left mouse click on the thumbnail and it will expand to ~1/4 NTSC size. If you would like to see it in a different size then click with the left mouse button on size and choose a new size.

• Reducing CPU load
  Every window you expand requires some additional shared memory space and more CPU to decode so you may overload your machine if you expand too many windows. If you are not watching a video window you might want to hit the mute button next to it and your machine will still receive that video feed from the network but it will not bother to decompress and display it. You can also reduce the CPU load by reducing the number of frames/second the video is decoding. THe thumbnail picture is decoded at a much lower rate than an expanded picture. If you click on the modes button on an expanded window and turn on the "Save-CPU" mode then the expanded picture will only be decoded as often as the thumbnail.

Launching vic from the command line

• Launching a multicast session
  There are several things you need to know about the session you are trying to join in order to launch vic from the command line. You will need to know the multicast address and port that you wish to send and receive vic transmissions on. The multicast address will normally look like an IP address but the first number will be probably be 224 (a class D address). The port will normally be a 4-5 digit number. You will also need to specify a time-to-live (ttl) for the session. The ttl corresponds to how many hops through the network the packets in the session can make. A ttl of 1 will keep the packets on the local subnet and a ttl of 127 will allow the packets to go throughout the world (something between these two values is probably what you want). The command to start vic is then

  vic -t ttl multicastaddr/port so an example command might be

  vic -t 16 224.35.36.37/4567
  

  The above command would launch vic on the multicast address 224.35.36.37 and port 4567 with a ttl of 16. The ttl of 16 is normally used to keep a multicast confined to a site.

  Launching a unicast session

  When launching vic as a unicast session you need to specify the other host participating in the unicast session on the command line. There can be no more than two participating machines. The port specified is the same on both machines and ttl is not needed since it only applies to multicast. If you are trying to start a unicast between tweety.lbl.gov and george.mit.edu on port 12345 you would use the following commands.

  on tweety.lbl.gov

  vic george.mit.edu/12345 and on george.mit.edu the command would be

  vic tweety.lbl.gov/12345

Transmitting video

• Opening the menu
  The first thing you need to do is to click on the "Menu" button at the bottom of the vic window. This should pop up another window that contains all the vic controls.

  Setting the transmission rate

  There are two sliders near the top of the menu that say "Rate Control". The top slider defines the maximum bandwidth that you will use in transmitting video. The second one defines the maximum number of frames per second vic will transmit. You will normally want to keep the bandwidth between 10 and 128 kilobits/second (kbps) particularly if you are using a high ttl value on the transmission.

  Turning on transmission

  Click once on the "Transmit" button and then wait until the square on the button turns red. If an error or a black screen pops up while trying to transmit, see "Debugging vic". Note: The vic menu often pops up over the original vic window so you may need to move the menu to one side to see your transmission.

  When you exit vic, do not forget to STOP THE TRANSMISSION by clicking on the RELEASE button. Otherwise, your capture device will not be freed and you will have to reboot your computer to be able to start another transmission or any other program using the drivers for this device.

Debugging vic

• Waiting for video
  When vic pops up, if you see the message "Waiting for video" then your vic is not receiving any video. It is either because there are no sites transmitting video on this address yet or there could be a delay before you start receiving video packets because the traffic was not previously being routed to you and only started coming to you when you activated your vic.

  Unable to open xxxxx

  If you are trying to transmit video and when you click on transmit you get an error indicating that vic is unable to open the video capture card. In the Encoder section of the vic menu there is a button called "Device...". If you click on the device button you should get a choice of several video cards. Itteratively try each one and hit transmit until you find the card installed on your machine. If none of the options can be opened by vic then your video capture card is probably not installed correctly.

  CapDriver Connect xxxxx

  If you are trying to transmit video and when you click on transmit you get an error with this kind of message, it means that the drivers for your capture device are already in use. Be sure to close any other program which is using this driver. If you have exited a vic session without releasing the transmission you might have to restart your computer...

  Transmitting a black picture

  If the thumbnail image that pops up when you start transmitting shows a black box and not what the camera is looking at, there are several things to check. The first thing to do is to click on "Port..." in the "Encoder" section of the menu and make sure that you are set to the same port as the camera is plugged in to. You shoulad also check that the camera is on, receiving power, is plugged into the video cable, and has the shutter open (all mistakes I have made at one time or another!).

Please also visit the

Lawrence Berkeley National Laboratory Home Page.

Distributed Systems Department Home Page.

Distributed Collaboratoratories Home Page.

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This document was last updated on August 18, 1997, and is located at http://www-itg.lbl.gov/OldMisc/mbone/vic.begin.html.

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