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Digi Cipher是一种全数字化HDTV制式,它可在一个6MHz的VHF或UHF频道内传送,并能以实际上觉察不出的传输图像损伤(由噪波、多径传输和干扰等所引起的)来提供HDTV所需性能。它有很高的图像质量,而解码器又不复杂并且可以采用低发射功率,因而它在空频道或未用频道上用作同时联播HDTV节目时是很理想的。Digi Cipher HDTV系统也能用于HDTV的电缆和卫星传输。在卫星传输Digi Cipher方面,绝对不存在要加大卫星接收抛物而反射器尺寸的牵制(与FM—NTSC或FM—PAL制相比)。这不仅对直播卫星(DBS)来说是重要的,而且对广播和电缆电视来说也是重要的,因为广播网和电缆电视节目通常是要通过卫星转播至联播台的。为了在缆电一个6MHz带宽内满足HDTV的全部性能要求,采用了以DCT(离散余弦变换)变换编码为基础的高效而独特的压缩算法。通过了详尽的计算机仿真,使该压缩算法完善化和最佳化。计算机的仿真结果显示出各种不同HDTV节目的优异图像质量。为了实现数字数据的无误差传输,采用了纠错码和自适应均衡性。可以实现当C/N比为19dB时的无误差接收。该系统已在今年5月的美国Las Vegas的国际广播会议上演示,图像从发明该系统的General Instruments公司总部的所在地通过卫星传输至Las Vegas的展出中心,其完美的HDTV图像质量受到广播电视业各界人士的极大关注。
Digi Cipher is a fully digitized HDTV format that can be delivered in a 6MHz VHF or UHF channel and can deliver virtually imperceptible transmission image impairments (caused by noise, multipath, interference, etc.) To provide the required performance for HDTV. It has high image quality, and the decoder is uncomplicated and can use low transmit power, so it is ideal for simulcasting HDTV programs on either null or unused channels. The Digi Cipher HDTV system can also be used for HDTV cable and satellite transmission. In satellite transmission Digi Cipher, absolutely no satellite receiver parabolic reflector sizes (as compared to FM-NTSC or FM-PAL). Not only is this important for direct broadcast satellites (DBSs), but it is also important for broadcast and cable television, as broadcast networks and cable television programs are usually broadcast to affiliate stations via satellite. To meet the full HDTV performance requirements within a 6MHz bandwidth of a cable, an efficient and unique compression algorithm based on DCT (Discrete Cosine Transform) transform coding is used. Through a detailed computer simulation, the compression algorithm to improve and optimize. Computer simulation results show excellent image quality for various HDTV programs. In order to achieve error-free transmission of digital data, error-correcting codes and adaptive equalization are used. Error-free reception when the C / N ratio is 19 dB can be achieved. The system was demonstrated at the International Broadcasting Conference in Las Vegas, USA, in May this year. From the location of General Instruments headquarters where the system was invented, it was transmitted via satellite to the Las Vegas show center. Its perfect HDTV image quality was influenced by radio and television Professionals from all walks of life great concern.