3:1 for chrominance) and the two color difference signals are transmitted on alternate lines, further increasing compression. The color space was YPbPr, with a luminance component and red blue color difference chrominance components. Audio and scrambling (selective access) Audio, in a format similar to NICAM was transmitted digitally rather than as an FM sub-carrier. The MAC standard included a standard scrambling system, EuroCrypt, a precursor to the standard DVB-CSA encryption system Technical details In MAC color is encoded using the YPbPr color space. Luma () is derived from red, green, and blue () after gamma-correction (formula similar to PAL): Color information is computed based on and differences, generating two compressed and weighted color-difference signals know in older MAC references as and or and . To avoid any confusion, and since the signals are analogue and bi-polar, these terms were replaced by and . and are used to transmit chrominance. On C-MAC, D-MAC and D2-MAC the following formulas apply: Luminance signal range is -0.5 to 0.5 volts; color difference signals vary between -0.65 to 0.65 volts. The following table lists the main technical parameters of the various MAC variants: MAC system innovations Mathematical A-MAC proved the mathematical principle that separating vision from colour for TV transmission was technologically viable. Broadcast engineering The MAC audio subsystem is very similar to NICAM, so much so that identical chip-sets are used. Broadcast engineering D-MAC satellite broadcasts provided the first broadcast sourced wide-screen television in Europe, and HD-MAC provided the first HDTV broadcasts, in 1992. Technical challenges Although the MAC technique is capable of superior video quality, (similar to the improvement of component video over composite in a DVD player), its major drawback was that this quality was only ever realized when the video signals being transmitted remained in component form from source to transmitter. If at any stage the video had to be handled in composite form, the necessary encoding/decoding processes would severely degrade the picture quality. Terrestrial TV broadcasters were never able to take full advantage of MAC image quality due to multiple interactions between their composite and component signal paths. Direct to Home and TVRO broadcasters were able to take advantage of MAC's improved image quality because their studios and routing facilities were far less complex. The success of NICAM audio for terrestrial television can be traced to the success of MAC technology. The MAC audio subsystem is nearly identical in design