The simultaneousPAL transmission of all TV-picture elements and the multiplexed transmission of the TV picture elements with D2-MAC.Simulated MAC signal. From left to right: digital data, chrominance and luminance
B-MAC[1] is a form of analog video encoding, specifically a type ofMultiplexed Analogue Components (MAC) encoding. MAC encoding was designed in the mid 80s for use with Direct Broadcast Satellite systems. Other analog video encoding systems includeNTSC,PAL andSECAM. Unlike theFDM method used in those, MAC encoding uses aTDM method. B-MAC was a proprietary MAC encoding used byScientific-Atlanta for encrypting broadcast video services; the full name was "Multiple Analogue Component, Type B".
B-MAC uses teletext-style non-return-to-zero (NRZ) signaling with a capacity of 1.625 Mbit/s. The video and audio/data signals are therefore combined at baseband.
Both PAL (626/50) and NTSC (525/60) versions of B-MAC were developed and used.
User base (PAL/NTSC zones)
This system was used in South Africa[2] and Australia[3] (forTVRO until 2000).
MAC transmits luminance and chrominance data separately in time rather than separately in frequency (as other analog television formats do, such as composite video).
Audio and Scrambling (selective access)
Audio, in a format similar toNICAM was transmitted digitally rather than as an FM subcarrier.
The MAC standard included a standard scrambling system, EuroCrypt, a precursor to the standard DVB-CSA encryption system.
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