MBONE: Multicasting Tomorrow's Internet
Video in Your New Event
The network video package, nv, is a videoconferencing tool that uses a default band-width of 128 Kbps and offers video rates of three to five frames per second. Versions are available for Sun, Silicon Graphics, DEC, and Hewlett-Packard systems. In Figure 5-4, you can see the main NV window. NV was one of the MBONE tools that was started as part of our new session.
The NV window is divided into five parts:
Figure 5-4: The main NV window.
- The participants who are sending video. You can see them and their identity in the form of fingernail video clips.
- The conference information. This part includes the multicast address of the conference (which really is a group), a port number, your name, the TTL of the session, and a channel number.
- I do not have a video camera and a frame grabber for my workstation, but I can still send video by choosing the X11 grabber from the Grabbers menu. In this section, you have the controls for the X11 grabber. By selecting Pointer, I can send that part of my desktop that surrounds my mouse pointer as a video signal. I also can choose to grab from a fixed area of my screen or a single window.
- The video transmit options are used to limit the amount of video data I'll be sending onto the network. The default is 128 Kbps. I am sending a small color image so that I use the least possible amount of bandwidth.
- The video receive options are used to control how I see the video I am receiving. Selecting double size for the size of the picture window, as shown in Figure 5-5, makes the window bigger, but the pixels of the image get bigger, also. It can be useful if you have an audience watching at your screen. Selecting double size also asks more of your machine in terms of processing. If you have a machine that would benefit from a smaller image so that the load of the machine does not suffer too much, selecting half size will do that for you. You can also adjust the contrast and brightness of the image to your liking.
Figure 5-5: The NV picture window.
When you click on a fingernail picture, the image of the fingernail appears in a normal-size picture window, as shown in Figure 5-5. You can have as many windows as there are people sending video to your event. In this window, you see the status of the actual broadcast in terms of frame rate, bandwidth, and packet loss. The brightness and contrast controls are still there, so you have per-picture control of these parameters. A Capture button allows you to capture a frame and save it to a file.
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