As the technology of high-definition television (HDTV) displays matures, the quality of analog video and audio processing will eventually make TV sets different. Digital processing in HDTV (including image scaling, de-interlacing, and MPEG demodulation) continues to play an important role, but these functions will soon become standardized. The analog processing of video and audio signals in HDTV directly affects the user's "TV viewing experience." However, HDTV manufacturers are quickly seeking improvements in the design of analog circuits for their televisions to increase sales and profits. This article will discuss some issues and design considerations for high-performance analog signal processing in HDTV. In liquid crystal (LCD) TVs and plasma (PDP) TVs, flat panel displays themselves have historically differed in the main performance of HDTV TVs. The development cost of seventh- and eighth-generation LCD flat panel displays has reached billions of dollars, but recent enhancements in PDP displays have forced some companies to form joint ventures to share their financial resources and technology. Currently, almost all leading manufacturers of LCD TVs and PDP TVs are joint ventures with other TV manufacturers that mainly produce display designs. This has caused "fair competition" regarding the performance of LCD and PDP displays. The display screens produced by these joint ventures are currently used in several competitive HDTV models from different TV manufacturers. Even in the emerging stage of high-definition digital broadcasting, HDTV still requires analog and digital interfaces. We need composite, component, and RGB signal analog interfaces to support older standard definition (SD) devices, such as video recorders (VCRs), camcorders, DVD players, and personal computers (PCs). Since users expect their SD TV programs to have the same quality as high-definition (HD) TV programs, high-performance analog interfaces must be designed. The integrated multi-format video decoder (eg ADV7403 from Analog Devices) contains a high-performance video decoder for composite video signals and a three-channel analog-to-digital converter (ADC) for digital component analog video and RGB. When designing an analog interface, it is important to provide a clean, low-noise power supply and use short printed circuit board (PCB) connections from the connector to the device input. We also recommend using a PCB design with a complete ground plane to minimize total PCB noise and reflection. Shortening the length of the printed line at the digital output (including data and clock) helps reduce the possibility of high-frequency signal reflection, which can destroy the integrity of the signal. Because the analog YUV signals recorded in DVD movies have a 10-bit resolution (which can represent more than one billion different colors), it is important to choose an analog interface that accurately reproduces colors using an ADC with a 10-bit (or higher) resolution. For example, ADI's ADV7403 multi-format video decoder integrates a 12-bit, 140MHz ADC to improve image quality to the greatest extent possible. Block diagram of ADV740312bit multi-format video decoder Audio processing in HDTV has several interesting design challenges. TV sets that tend to be narrow will inevitably result in a reduction in the size of the speakers while reducing the space required for heat dissipation by the amplifier. Since HDTV is usually used as a home theater, the audio circuit in the TV must support the latest surround sound and bass enhancement algorithms. HDTV must complete these major improvements in SD audio while achieving the ambitious goal of low cost and early market launch. Cathode ray tube (CRT) displays SD TVs can only reproduce stereo (2.0 audio) and have a large TV case that is easy to place speakers of appropriate size. HDTVs that use LCD or plasma displays have a narrow TV housing and can only use smaller-sized speakers, thus limiting acoustic performance. HDTV TV programs are played in surround sound (5.1 audio), so audio design engineers must design high-quality audio products so that HDTV can work under these constraints while still meeting stringent cost requirements. Currently, design engineers can use a programmable audio processor to develop a single-speaker audio platform that can be integrated into different models of HDTV products that can use speakers of various sizes. Design engineers have developed new audio processor algorithms using the latest psychoacoustic research results. This algorithm uses two or three speakers in HDTV to provide listeners with sound from the experience of a complete multi-speaker surround sound system. ADAV400 programmable audio processor block diagram In order to properly support popular third-party virtual surround and surround sound algorithms, the audio processor must include an audio codec and a digital-to-analog converter (DAC) with excellent analog performance. For example, ADI ’s ADAV400 with active equalization technology (used to compensate for narrow speakers) supports popular third-party algorithms and the analog performance needed to produce full, rich sound. Graphical software tools (eg SigmaStudio) allow complete control of the entire sound environment. Extended audio algorithm library Finally, Class D audio amplifiers can minimize the size of heat sinks and other external devices, making them suitable for the narrow spaces of new HDTV products. The use of large CRTs in CRT TVs leaves audio design engineers with a large chassis space, allowing CRT TV audio design engineers to use Class AB amplifiers, which are inefficient and usually require large heat sinks. Design engineers can make their audio amplifier circuits fit their narrow spaces by using high-efficiency Class D audio amplifiers such as ADI's AD1991 (efficiency> 85% at full power), without compromising audio quality or power output.
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