Digital television has become increasingly popular due to the high quality video image it provides, along with informational and entertainment features, such as pay-per-view, electronic program guides, video-on-demand, stock, weather and stock information, Internet hyperlinks, and so forth. Such television data can be communicated to a user via a broadband communication network, such as a satellite or cable television network, or via a computer network. The progression from terrestrial television broadcast to cable television, to DTH satellite television has allowed consumers to obtain more and more programming information while limiting the costs that are passed to the consumers. Currently, there are two ways to transmit data to a television (TV) receiver, the terrestrial transmission for the conventional TV and the cable transmission for cable TV. Both the terrestrial and cable transmission use the vestigial sideband (VSB) modulation, by which the data is transmitted by multilevel symbols. The established standard data levels for the VSB signals are 2VSB with 2 symbol levels, 4VSB with 4 symbol levels, 8VSB with 8 symbol levels, and 16VSB with 16 symbol levels. The data level with the higher symbol levels can transmit greater data. However, as the data level increases, the number of symbols and the interspace between the symbols correspondingly decrease, resulting in a low signal to noise ratio (SNR). Recent developments in the field of video signal processing have produced digital high definition television (HDTV) signal processing and transmission systems. However, all of the DTH programming has been standard definition television (SDTV), which is also called conventional definition television (CDTV). Digital high definition television production schemes typically produce higher quality television images and sound than conventional television systems. High definition television (HDTV) has a resolution of approximately twice that of SDTV in both the vertical and the horizontal dimensions. HDTV provides motion picture video resolution and CD-quality sound to a viewer at home. Transmission of digitized television signals makes it possible to deliver video images of a much higher quality than that of analog signals. When an image signal comprising a sequence of image "frames" is expressed in a digital form, a substantial amount of data need be transmitted, especially in the case of high defition television system.

High definition television systems use digitally encoded signals having extremely high clock signal frequencies which are not directly compatible with the conventional video recording processes. A high definition television (HDTV) signal generally contains image information with approximately twice the horizontal and vertical resolution of a standard television image (e.g., NTSC), and with a wider aspect ratio compared to a standard television image. Basically, the HDTV signal can be encoded and decoded into various video formats with no limitation to a single video format. The HDTV signal can be encoded and decoded into six video formats, an interlaced scanning format with 1050 vertical scanning lines and a field rate of 60 Hz, progressive scanning formats with 1050 vertical scanning lines and frame rates of 24 Hz and 30 Hz, and progressive scanning formats with 787.5 vertical scanning lines and frame rates of 24 Hz, 30 Hz and 60 Hz. High definition television devices and high quality standard definition television, typically use an analog YPbPr (or RGB) three wire component video input wherein the synchronization signals are embedded with the luma and chroma information. The high definition television signal consists of a combination of red (R), green (G) and blue (B) signal components (referred to as a RGB signal hereinafter) or one luminance signal (Y) and two color-difference signal components. Each signal component of the RGB signal has a bandwidth of 30 MHz. The NTSC signal is an analog signal in which the baseband video frequency bandwidth is six megahertz. NTSC television receivers and recorders are easily made compatible since video tape recording systems operate very well in response to analog signals and because the six megahertz bandwidth of the NTSC signal is well within the response frequency of currently available tape and tape recorders. An HDTV signal exhibits a greater image aspect ratio than the aspect ratio of a standard NTSC television image. An HDTV signal may be broadcast using a simulcast technique, where two versions of the same program material are broadcast simultaneously via separate standard 6 MHz channels. One of the two program versions contains standard definition NTSC information broadcast on one channel, while the other contains high definition information broadcast on the other 6 MHz channel.

The Advanced Television Systems Committee (ATSC) standard for digital high definition television (HDTV) transmission is adopted by the Digital High Definition Television (HDTV) Grand Alliance (Grand Alliance) is a group of television manufacturing and research organizations in the television industry. The ATSC standard for HDTV transmission over terrestrial broadcast channels uses a signal that consists of a sequence of twelve independent time-multiplexed trellis-coded data streams modulated as an eight level vestigial sideband (VSB) symbol stream with a rate of 10.76 MHz. This signal is converted to a six MHz frequency band that corresponds to a standard VHF or UHF terrestrial television channel, over which the signal is then broadcast. The ATSC standard defines a data segment as a length of data having eight hundred thirty two (832) symbols. Each data segment begins with a fixed pattern comprising the four symbols "1001". The fixed pattern of "1001" indicates the start of a new data segment. HDTV digital video data is compressed and encoded using the MPEG-II format into a data stream known as the DTV transport layer. The ATSC standard for transmission uses an RF modulation format called 8-VSB (8 level vestigial side band) as the means to convey the DTV transport layer from a television transmitter to one or more television receivers. MPEG-2 video is used to support both high-definition television (HDTV) and standard-definition television (SDTV). The video frames in HDTV are of higher resolution than those used in present NTSC signals while the video frames of SDTV have approximately the same resolution per frame as the existing analog NTSC standard. The MPEG-2 standard defines a complex syntax which contains a mixture of data and control information. Some of this control information is used to enable the signals having several different formats to be covered by the standard. These formats define images, having differing numbers of picture elements (pixels) per line, differing numbers of lines per frame or field and differing numbers of frames or fields per second. MPEG-2 video coding employs a motion-compensated discrete cosine transform (DCT) algorithm. The DCT exploits spatial redundancy, and motion compensation exploits temporal redundancy. To perform motion compensation in frame mode, the MPEG-2 video decoder should have a capacity to store two reconstructed frames. In MPEG-2 several different profiles are defined, each corresponding to a different level of complexity of the encoded image. For each profile, different levels are defined, each level corresponding to a different image resolution. Using MPEG encoding techniques, HDTV signals having a data rate of between 600 and 1200 megabits per second (Mbps) can be compressed to produce a signal having a data rate of less than 20 Mbps. In order to be so-called "spectrum compatible", high definition television systems are required to fit more high frequency video information into the standard six megahertz transmission channel bandwidth to achieve their high resolution or high definition performance.

A HDTV receiver receives an HDTV broadcast so that a user can view the broadcast. In an HDTV system, a synchronizing signal is added before a signal is transmitted in a unit of a horizontal line from a TV broadcasting station. A receiver receiving the transmitted signal detects the synchronizing signal from the transmitted signal, synchronizes the transmitted signal with a horizontal line signal, and then processes the synchronized signal. The digital video signal is encoded (compressed) and transmitted in units of image blocks through DCT processing in a transmitter. The transmitted encoded video signal is restored to its original state through inverse DCT processing in a receiver. There are many ways to encode high definition television (HDTV) signals. These techniques can generally be classified as waveform coding, transform coding and vector quantization techniques. Waveform coding techniques such as pulse code modulation (PCM) typically use a scalar quantizer to quantize analog samples. The transform coding techniques transform the image samples to the transform domain, achieving energy compaction. Sub-band coding is a coding technique which divides the HDTV signal into many small bands. Vector quantization (VQ) basically quantizes a group of samples at one time. VQ has the advantage that only a table look-up operation is needed to decode the signal, leading to an extremely simple decoder. Because of the relatively large amount of data required to represent each HDTV frame, HDTV decoders must support higher data rates than SDTV decoders. A digital transcoder may be located at an intermediate stage in the transmitting chain or as part of a telecommunication network such as at a head-end or at a network switch. High definition television receivers may incorporate double conversion tuners in which the input RF signal is upconverted to a very high frequency, filtered and downconverted to a standard 44 MHz IF frequency. In VSB (vestigial side band), DSB (double side band), and SSB (single side band) communication systems, a transmitter transmits a carrier via a pilot signal, in order for a receiver to accurately recover the carrier.