7. Multichannel sound diffusion/distribution

7.1 Television

Broadcasting Dolby Prologic (Lt Rt) requires two channels. Since French analog television was monophonic, it could not be used. The arrival of the NICAM 728 system, and hence stereo, enabled its introduction. Countries where the sound component is frequency-modulated had stereo earlier and were able to broadcast Lt Rt.

In the MPEG-2 Transport Stream used for digital television broadcasting, multichannel sound can be encapsulated in different compression formats [ETSI TS 101 154] :

• Dolby D (the algorithm is called AC3). The bit rate is 384 kbit/s for television broadcast, and can go up to 640 kbit/s (it's around 320 kbit/s on 35 mm film, and 448 kbit/s on DVD);

• Dolby...