Multiplex (television)

A multiplex or mux, also known as a bouquet, is a grouping of program services as interleaved data packets for broadcast over a network or modulated multiplexed medium, particularly terrestrial broadcasting. The program services are broadcast as part of one transmission and split out at the receiving end. The conversion from analog to digital television made it possible to transmit more than one video service, in addition to audio and data, within a fixed space previously used to transmit one analog TV service (varying between six and eight megahertz depending on the system used and bandplan). The capacity of a multiplex depends on several factors, including the video resolution and broadcast quality, compression method, bitrate permitted by the transmission standard, and allocated bandwidth; statistical time-division multiplexing is often used to dynamically allocate bandwidth in accordance with the needs of each individual service. Each service in a multiplex has a separate virtual channel (also known as a logical channel number) for identification and tuning. Depending on the country, a multiplex may be controlled by one broadcaster offering multiple subchannels or may feature services from multiple broadcasters with separate licenses. Multiplexing has made it possible for many new free-to-air television services to be introduced, some of them expressly designed for carriage as additional channels. In the United States, such services are called digital multicast television networks or diginets. The term is also used in an otherwise unrelated sense to refer to additional channels offered by premium pay television services, such as HBO, similar to its meaning with regard to movie theaters.