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HDTV

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HDTV

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HDTV

  1. 1. G. H. Raisoni College of Engineering An Autonomous Institution under UGC Act 1965 |Accredited by NBA & NAAC ‘A’ Grade DEPARTMENT OF ELECTRONICS AND TELECOMMUNICATION ENGINEERING (2015-2016) TAE-1 “Activity Based Learning” Subject: Television Engineering “HDTV” Year/Semester: 3rdyear / 5th semester. Section: ‘C ’. Guided By: Prof. K.A. Kalbande Submitted by: Roll No. 30. Ashish Pandey
  2. 2. Report On HDTV Introduction:- Today the abbreviation “HD” is known almost to everyone. And it’s clear why: the notion “high definition” is applied to everything more or less associated with video production or playback – smartphones, camcorders, monitors, glasses, etc. But most often we hear about high-definition television, or HDTV. Let’s figure out what it is and find answers to the most popular questions about HDTV. HDTV, standing for high-definition television, is a new means of television broadcasting and the machines that take advantage of it. HDTV broadcasts video digitally (in contrast to the common analog formats PAL, NTSC, and SECAM) and of higher 720 pixels or 1080 pixels resolution. Description:- HDTV (high definition television) is a television display technology that provides picture quality similar to 35 mm. movies with sound quality similar to that of today's compact disc. Some television stations have begun transmitting HDTV broadcasts to users on a limited number of channels. HDTV generally uses digital rather than analog signal transmission. However, in Japan, the first analog HDTV program was broadcast on June 3, 1989. The first image to appear was the Statue of Liberty and the New York Harbor. It required a 20 Mhz channel, which is why analog HDTV broadcasting is not feasible in most countries. HDTV and standard definition television (SDTV) are the two categories of display formats for digital television (DTV) transmissions, which are becoming the standard. HDTV provides a higher quality display with a vertical resolution display from 720p to 1080i. The p stands for progressive scanning, which means that each scan includes every line for a complete picture, and the i stands for interlaced scanning which means that each scan includes alternate lines for half a picture. These rates translate into a frame rate of up to 60 frames per second, twice that of conventional television. One of HDTV's most prominent features is its wider aspect ratio (the width to height ratio of the screen) of 16:9, a development based on research showing that the viewer's experience is enhanced by screens that are wider. HDTV pixel numbers range from one to two million, compared to SDTV's range of 300,000 to one million. New television sets will be
  3. 3. either HDTV-capable or SDTV-capable, with receivers that can convert the signal to their native display format. In terms of audio quality, HDTV receives, reproduces, and outputs Dolby Digital 5.1. In the United States, the FCC has assigned broadcast channels for DTV transmissions. In SDTV formats, DTV makes it possible to use the designated channels for multiple signals at current quality levels instead of single signals at HDTV levels, which would allow more programming with the same bandwidth usage. Commercial and public broadcast stations are currently deciding exactly how they will implement their use of HDTV. HDTV uses the MPEG-2 file format and compression standard. Block Diagram Transmitter: The video from the camera consists of the R, G, and B signals that are converted to the luminance and chrominance signals. These are digitized by A/D converters. The luminance sampling rate is 14.3 MHz, and the chroma sampling rate is 7.15 MHz. The resulting signals are serialized and sent to a data compressor. The purpose of this device is to reduce the number of bits needed to represent the video data and therefore permit higher transmission rates in a limited-bandwidth channel. MPEG-2 is the data compression method used in HDTV. The MPEG-2 data compressor processes the data according to an algorithm that effectively reduces any redundancy in the video signal. For example, if the picture is one-half light blue sky, the pixel values will be the same for many lines. All this data can be reduced to one pixel value transmitted for a known number of times. The algorithm also uses fewer bits to encode the color than to encode the brightness because the human eye is much more sensitive to brightness than to color. The MPEG-2 encoder captures and compares successive frames of video and compares them to detect the redundancy so that only differences between successive frames are transmitted. The signal is next sent to a data randomizer. The randomizer scrambles or randomizes the signal. This is done to ensure that random data is transmitted even when no video is present or when the video is a constant value for many scan lines. This permits clock recovery at the receiver. 8.4 MHz Camera ADC MPEG-2 data compression Sync Header Audio source Other audio sources 8-Level signal Balanced modulator Carrier generator Local oscillator Power amplifier Antenna Serial
  4. 4. video data Packetizer Packetizer MPX Frame formatter SB filter Data scrambler ADC AC- 3 data compression Trellis encoder Reed-Solomon error detection MPX DAC Up converter (mixer) Figure 23-27 HDTV transmitter. 32 Chapter 23 Next the random serial signal is passed through a Reed-Solomon (RS) error detection and correction circuit. This circuit adds extra bits to the data stream so that transmission errors can be detected at the receiver and corrected. This ensures high reliability in signal transmission even under severe noise conditions. In HDTV, the RS encoder adds 20 parity bytes per block of data that can provide correction for up to 10 byte errors per block. The signal is next fed to a trellis encoder. This circuit further modifies the data to permit error correction at the receiver. Trellis encoding is widely used in modems. Trellis coding is not used in the cable TV version of HDTV. The audio portion of the HDTV signal is also digital. It provides for compact disk (CD) quality audio. The audio system can accommodate up to six audio channels, permitting monophonic sound, stereo, and multichannel surround sound. The channel arrangement is flexible to permit different systems. For example, one channel could be used for a second language transmission or closed captioning. Each audio channel is sampled at a 48-kbps rate, ensuring that audio signals up to about 24 kHz are accurately captured and transmitted. Each audio sample is converted to an 18-bit digital word. The audio information is time- multiplexed and transmitted as a serial bit stream at a frequency of A data compression technique designated AC-3 is used to speed up audio transmission. Receiver:- An HDTV receiver picks up the composite signal and then demodulates and decodes the signal into the original video and audio information. A simplified receiver block diagram is shown in Fig. 23-30. The tuner and IF systems are similar to those in a standard TV receiver.
  5. 5. From there the 8-VSB signal is demodulated (using a synchronous detector) into the original bit stream. A balanced modulator is used along with a carrier signal that is phase-locked to the pilot carrier to ensure accurate demodulation. A clock recovery circuit regenerates the clock signal that times all the remaining digital operations. The signal then passes through an NTSC filter that is designed to filter out any one channel or adjacent channel interference from standard TV stations. The signal is also passed through an equalizer circuit that adjusts the signal to correct for amplitude and phase variations encountered during transmission. The signals are demultiplexed into the video and audio bit streams. Next, the trellis decoder and RS decoder ensure that any received errors caused by noise are corrected. The signal is descrambled and decompressed. The video signal is then converted back to the digital signals that will drive the D/A converters that, in turn, drive the red, green, and blue electron guns in the CRT. The audio signal is also demultiplexed and fed to AC-3 decoders. The resulting digital signals are fed to D/A converters that create the analog audio for each of the six audio channels. Conclusion The development of HDTV is in its very final stages, with implementation slated for 2006. Issues that will have to be worked out include compression, bandwidth allocation, development of accepted standards in resolution and aspect ratio, and finally widespread conversion throughout the United States. By the time that conversion takes place, consumers will have had to chose one of a number of varying options in order to take advantage of HDTV. At base terms, what sets HDTV apart from the current television system is that it has:  Wider images  Much more sharpness and clarity  5.1 channel CD-quality Dolby Digital (AC-3) surround sound  Digitally transmitted signals - eliminating snow, double images, and picture sparkles. With all the hype surrounding it, much like the conversion from black and white to color television, if HDTV is to be considered successful when implemented, it will have brought the nation a stunning leap in their television experience with unparalleled image quality, vastly improved sound, and a new reliability that makes the current NTSC system pale in comparison. Reference:- 1. www.tripod.com 2. www.google.com 3. https://en.wikipedia.org/wiki/High-definition_television 4. www.webopedia.com

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