CONFERENCE EQUIPMENT OUTSIDE ROOM ENCE CODEC MODEM CoNTRO TO CENTRAL CONTROL CENTER FIGURE 102.10 A generic videoconference system. does not need to see the audience, such as a speech from a senior corporate executive. In a point-to-multipoint conference, multiple sites can receive a transmitting site. Two of the primary sites are fully interactive with each other. A feature called multipoint switching has been implemented in some commercial systems. This feature allows switching of receive and transmit sites during the conference. The multipoint switching feature can be provided using either a TDMA or SCPC system. A TDMA system allows multiple sites to transmit and receive in a mesh configuration. An economical multipoint switching system is possible with SCPC using only two transmit frequencies In a "chair"controlled conference, the chair is assigned one of these frequencies for the duration of the conference. Dynamic allocation of the second frequency is controlled by the chair to any of the participating sites at any time during the conference Video broadcast Video broadcast over satellite is attractive for industry segments such as educational TV, distance learning, usiness television, and television receive-only (TvRO)applications. Business television allows users to transmit broadcast-quality video programming from a studio to any number of specified locations equipped with TVROs a video broadcast capability, as an overlay to interactive data networks, is becoming increasingly popular for corporate presentations, education, and training A video uplink consists of a video exciter, HPA, antenna, and optionally an encryption system such as B-MAC multiplexed analog component, version B)encoder, for business video broadcasts. Each remote VSAT must be configured to receive the video transmission. This involves adding a video receiver at each VSAT location that plugs into the VSAT IDU Audio/video signals from the video receiver can be presented directly or through a b-mac decoder to a standard tv monitor The digital compressed video signal can be used as a replacement for an analog video distribution. Digital coding technology can be used to compress video signals to reduce data rates to 2 Mbps or even lower and produce near broadcast-quality video. Distribution of digital video signals at such rates requires less tran- ponder bandwidth and a smaller antenna at remote terminals. Compression techniques used are based on one or a combination of the following: inter/intra-frame prediction, adaptive differential transform, conditional replenishment, discrete cosine transform, adaptive prediction, motion compensation, and vector quantization Satellite News Gathering tellite news gathering(SNG) is used for live, on-the-spot coverage and news exchanges with other commercial broadcast stations. This is made possible by the availability of occasional-use space segment and transportable earth stations on news trucks. An SNG systems consists of a compact earth station and video/audio transmission e 2000 by CRC Press LLC© 2000 by CRC Press LLC does not need to see the audience, such as a speech from a senior corporate executive. In a point-to-multipoint conference, multiple sites can receive a transmitting site. Two of the primary sites are fully interactive with each other. A feature called multipoint switching has been implemented in some commercial systems. This feature allows switching of receive and transmit sites during the conference. The multipoint switching feature can be provided using either a TDMA or SCPC system. A TDMA system allows multiple sites to transmit and receive in a mesh configuration. An economical multipoint switching system is possible with SCPC using only two transmit frequencies. In a “chair” controlled conference, the chair is assigned one of these frequencies for the duration of the conference. Dynamic allocation of the second frequency is controlled by the chair to any of the participating sites at any time during the conference. Video Broadcast Video broadcast over satellite is attractive for industry segments such as educational TV, distance learning, business television, and television receive-only (TVRO) applications. Business television allows users to transmit broadcast-quality video programming from a studio to any number of specified locations equipped with TVROs. A video broadcast capability, as an overlay to interactive data networks, is becoming increasingly popular for corporate presentations, education, and training. A video uplink consists of a video exciter, HPA, antenna, and optionally an encryption system such as B-MAC (multiplexed analog component, version B) encoder, for business video broadcasts. Each remote VSAT must be configured to receive the video transmission. This involves adding a video receiver at each VSAT location that plugs into the VSAT IDU. Audio/video signals from the video receiver can be presented directly or through a B-MAC decoder to a standard TV monitor. The digital compressed video signal can be used as a replacement for an analog video distribution. Digital coding technology can be used to compress video signals to reduce data rates to 2 Mbps or even lower and reproduce near broadcast-quality video. Distribution of digital video signals at such rates requires less tran￾sponder bandwidth and a smaller antenna at remote terminals. Compression techniques used are based on one or a combination of the following: inter/intra-frame prediction, adaptive differential transform, conditional replenishment, discrete cosine transform, adaptive prediction, motion compensation, and vector quantization [Patterson and Delp, 1990]. Satellite News Gathering Satellite news gathering (SNG) is used for live, on-the-spot coverage and news exchanges with other commercial broadcast stations. This is made possible by the availability of occasional-use space segment and transportable earth stations on news trucks. An SNG systems consists of a compact earth station and video/audio transmission FIGURE 102.10 A generic videoconference system