➡ The Grand Alliance
The Digital HDTV Grand Alliance was formally established on May 24, 1993.
The seven-member companies of the Grand Alliance were AT&T, GI, MIT, Philips, Sarnoff, Thomson and Zenith.
Two key system elements, audio and transmission, could not be resolved by negotiation within the Grand Alliance, and so it was agreed that a “shootout” in the laboratory.
Audio and Transmission Shootouts:
The audio shootout occurred first. A multi-channel (5.1) surround sound system was required by the FCC to be included in the Grand Alliance system.
There were three candidates: Dolby’s AC-3, the MPEG-2 Layer 2 system and MIT’s AC system.
AC-3 was superior in some areas, because the MPEG-2 system had a technical flaw and problems with some test sequences. The MIT system was judged to be inferior to both.
After retesting, the Grand Alliance issued a statement that the MPEG-2 system was judged to be “equivalent in performance” to the Dolby system.
The transmission competition was between Zenith’s 8-level Vestigial Side Band (8-VSB) system and a 32-level Quadrature Amplitude Modulation (32-QAM) system provided by GI.
The HDTV prototype system was developed and constructed during 1994.
AT&T and GI developed the MPEG Video Encoder, while Philips provided the MPEG Video Decoder. Sarnoff built the Transport Encoder, and Thomson the Transport Decoder. Zenith built the modulation/demodulation system.
Dolby, who was not a Grand Alliance member, provided the Surround Sound Audio system shown in the below figure.
