The INTV! Station is used to capture audio and video and distribute it over the network. Proper setup and configuration of your INTV! Station software is the key to maximizing the performance and functionality of INTV!.

This chapter discusses:

• Starting an INTV! Station
• Files associated with the INTV! Station
• Tuning Station Performance

Before running the station, the INTV! Station software must be properly installed and licensed. You should also make sure that your video capture board is properly installed, and that you have your video input device properly connected.

Once the workstation is properly set up and configured, you are ready to run the INTV! Station. If this is the first time you have ever run the Station, it will appear with all of the factory default settings. In order to customize the settings, you must run the Admin Tool. The Admin Tool can only be run while the station is running. Usage of the Admin Tool is fully outlined in the Chapter 7, "The Admin Tool". You must run the station as a user who has write access to the directory, /etc/insoft in order for it to work. To run the station use the following command line:

<directory where INTV! is insta1led>/bin/station

This brings up the station, which will be ready to send data to users who tune in. After running the station for the first time, you should use the Admin Tool to select the video board you wish to use and configure the station.

The INTV! Station is set up to automatically send data to all viewers that are tuned in. If no viewers have the station tuned in, then the station does not broadcast data over the network in order to save bandwidth.

INTV! Stations employ multicast routing in order to lower network usage and improve station performance. With traditional unicast routing, a station would send a video and audio stream to every viewer that has the station tuned in. However, multicast sends only one stream of data, and the viewers automatically accept the packets intended for them. The advantages conferred by multicast routing are twofold. One, multicast saves system resources on the station since it must only send out one stream over the network. Two, network bandwidth is saved because no matter how many viewers are tuned in, only one audio and one video stream per station is broadcast.

Using the Admin Tool (described in the next chapter), stations can be configured so as to maximize performance and minimize network usage. There are a number of audio, video, and network options that can be set in order to improve video or audio quality, minimize network bandwidth consumption, or balance between these two to optimize INTV!’s performance for each user’s particular configuration.

For the most part, video performance is based on three factors: frames per second, frame size, and your compression setting. These three settings have a large effect on both network bandwidth usage and the system performance of the machine running the viewer. Frames per second and video size must be set with both of these constraints in mind in order to perform within the context of your network.

If your frame size is too large, or you have selected too many frames per second, then the viewers will often receive or display many frames less than are being sent. Not only does this waste network bandwidth, but it also degrades performance because the extra data "chokes" the viewer and causes it to actually display less frames than it could if the frame rate were set properly. Under most configurations, the tradeoff between frame size and frame rate is significant. This is particularly true for full size frames. Unless you are in a situation that you have a specific ceiling on the amount of bandwidth you can use, you should attempt to match as closely as possible the number of frames per second that your station sends to the number of frames per second that the viewer can effectively process. Your compression setting determines how much your software compresses the video data before it is broadcast. Setting your video compression to a high value will deteriorate the picture quality that viewers receive.

INTV! supports three data compression standards: JPEG, CellB, and H.261.

CellB—CellB compression was developed by Sun Microsystems to support compression and decompression of video with minimal hardware requirements. CellB is supported by all INTV! platforms.

JPEG—JPEG, developed by the Joint Photographic Experts Group, generally produces the highest quality video image, but requires more processing power than other compression algorithms. JPEG requires substantial processing power to decompress in software, so you will generally want to use this compression algorithm only on fast workstations.

H.261—H.261 is a video compression standard developed by the International Telecommunications Union. H.261 is designed to provide maximum quality while at the same time minimizing bandwidth usage. Like JPEG, compression and decompression of H.261 streams requires considerable processing power.

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