The next generation of digital TV decoding, powerful CPU is the basic requirement

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Digital TV technology will bring a new era of audiovisual and entertainment to consumers and the TV industry. But before digital TV can enter the households of ordinary consumers, several issues must be resolved: In a rapidly changing market environment, how can manufacturers quickly and economically develop the products consumers need? How to realize the perfect integration of image, video and interactive data processing functions at low cost? How to overcome the inconsistency of global digital TV software and hardware standards? This article will analyze the shortcomings of the current digital TV set-top box solutions to these problems, and discuss the problems that the next generation products need to solve in terms of structural system.

Defects of the current digital TV program

Certain defects of current digital TV set-top boxes have restricted the development and popularization of digital TV. The root cause of these defects is the set-top box application specific integrated circuit chip (ASIC). The key function of the set-top box is realized by the digital TV decoder. The decoder component is responsible for the reception and display of digital TV broadcasting, demultiplexing the digital transmission information stream and decoding the MPEG-2 audio / video data stream information, and implementing the graphic functions of the set-top box. Figure 1 is a typical functional block diagram of a current digital TV set-top box.

The following are the shortcomings of the current digital TV decoder using this design.

1. Cannot support multiple display formats

Digital TV broadcasts around the world use different transmission formats, including ATSC in the United States, ARIB in Japan, and DVB in the European Union, which define different digital TV video formats. Even in the United States, there are 18 different display formats, with resolutions ranging from 480i (equivalent to the resolution of current analog TV equipment) to 1080i on wide-screen high-definition TVs. The initial digital TV standard will include both standard definition television (SDTV) with 480 line resolution and high definition television (HDTV) with 720 line and 1080 line resolution. The TV station will decide which format to choose according to the requirements of different display formats on the complexity of transmission equipment and how to occupy the digital broadcasting frequency resources. Some broadcasters have stated that in order to provide viewers with more choices, they may deliver multiple SDTV programs instead of just one HDTV program that takes up a lot of bandwidth.

The design of the current digital TV decoder makes it unable to handle many existing display formats. Some digital TV decoders can support all formats of input, but do not output all display formats, which forces manufacturers to design different set-top boxes for standard-definition TV and high-definition TV. These design tasks need to be completed by different engineering teams, and the development tools they use are exactly the same. Therefore, for manufacturers, this has become a time-consuming and expensive task.

2. Expensive manufacturing costs

As shown in Figure 1, current set-top boxes use multiple chips to implement audio and video functions. The chips used in these set-top boxes use a 0.5-micron processing technology and are therefore larger in size. At the same time, in order to realize the mutual conversion between different display formats, it is necessary to use different chips. In addition, the memory used by the decoder is not optimized, and different functional modules use their own memories, wasting precious storage resources. This architecture increases the area of ​​the circuit board and makes the design more complicated. The low-integration, low-efficiency memory structure and the backward chip processing technology make the current decoder circuit costly and have low performance.

3. Can not support the constantly updated data service standards

The structure of the current digital TV decoder is closed and inflexible. They are incompatible with WindowsCE, PersonalJava, and ATSC application programming interfaces (APIs), so they cannot support current emerging data service applications, such as online banking, e-mail, and web browsing. If it can not support interactive applications, the current digital TV decoder is difficult to attract consumers too much.

4. Poor user interface

In order to handle interactive data services, the user interface must have a good visual experience, intuitive and easy to use. Due to the lack of a dedicated graphics processor, the current digital TV decoder has a poor user interface, slow application services, poor graphics quality, poor text display, and flickering screens. The current set-top box uses an embedded OSD processor in the MPEG-2 chip to manage text and graphics. Since it does not have graphics acceleration and anti-flicker circuits, and can only support 4-8 bit / pixel graphics formats, it is difficult for the OSD processor Provide users with a beautiful interactive interface.

5. Dedicated CPU with low performance

The current solution uses an embedded processor, which has insufficient performance and a processing capacity of only 20 MIPS or even lower, and they also use a dedicated bus. Emerging interactive data services based on the new API standards require powerful CPUs to provide real-time interactivity for viewers.

6. Closed structure and lack of flexibility

The structure of current digital TV decoder chips has no flexibility, cannot be converted, and does not support modularization. They use a dedicated bus and operating system. This structure prevents standard-definition display from being converted to high-definition display, or reverse conversion, and cannot provide greater flexibility for set-top box manufacturers. Its dedicated structure also excludes the possibility of modularization, so designers cannot add new standard peripheral components, such as I / O devices, modems and 3D graphics components.

Due to the above-mentioned defects, the current digital TV decoder failed to become a popular product on the market. On the contrary, they have only become a kind of props for technical demonstrations, which cannot really promote the development and popularization of digital TV.

Functional characteristics of the next generation digital TV decoder

1. Support multiple formats

At present, multiple standards of digital TV coexist in the world, even if there are multiple display formats within one standard, for example, ATSC has 18 display formats. The next-generation digital TV decoder must support multi-standard decoding or multiple formats under one standard. The decoder can't just decode, but also output all of it. A digital TV receiver or set-top box designed with an advanced decoder can receive all digital TV signals and can output in any display format. Such a decoder should have the ability to down-convert high-definition signals for display on a standard-definition television, or display standard-definition programs on a high-definition television. Full format support allows users to not miss any digital programs, regardless of the type of TV receiver they own. In addition, it must also support the analog transmission that still exists and the large number of analog TV devices installed. Through up-conversion, you can watch programs transmitted in analog format on digital TV; similarly, through down-conversion, you can also watch programs transmitted in high-definition format on analog TV.

2. Reduce costs

The next-generation decoder must integrate more functions on a single chip and use advanced processing technology (0.25 micron or 0.18 micron processing technology) to obtain a smaller chip size. In the current digital TV decoder structure, different chips are used to realize MPEG-2 audio / video decoding, transport stream TS (TransportStream) demultiplexing, graphics functions and display processing. These four functions are the key components in a digital TV receiver. By integrating all these functions in a single-chip digital TV decoder, costs can be significantly reduced. In addition, the reduced number of components can simplify the design of the circuit board, reduce the area of ​​the circuit board, and also facilitate the inventory management of the product, further reducing the cost of the digital TV manufacturer. The improvement of integration also makes the interface between different internal modules optimized, which helps to get better performance. In addition, in order to reduce storage costs, memory sharing can be achieved between video and audio functions.

3. Support for interactive data services

The next-generation decoder should be compatible with digital TV APIs such as WindowsCE and PersonalJava, and its structure must be flexible enough to support the API standards being developed by the ATSC and DVB committees. Supporting popular APIs can ensure that new data service applications such as online banking, online shopping, and Internet browsing are implemented through digital TV. Compatibility with future API standards will ensure compatibility for all future applications, which will extend the life of the product.

4. Attractive user interface

The user interface has a critical impact on the success of interactive data devices. The menus and controls displayed on the screen must be easy to use, visually attractive, and intuitive to understand so that consumers can feel comfortable with online applications. The next-generation decoder chip must integrate a dedicated graphics processor to provide consumers with a good visual experience. In order to display bright colors, the decoder chip should support a higher color resolution (16 bits / pixel or higher); in order to achieve a faster response time, to seamlessly integrate video and graphics content, graphics acceleration must be performed, For example, graphics memory block movement and hardware cursor. In order to obtain a high-quality display effect on an interlaced TV screen, the graphics processor must have an anti-flicker circuit; in order to make the text displayed on the screen clearer, it should also support anti-aliasing; the hardware cursor facilitates flexible menu selection . For e-commerce and other online services developed on digital TV to further develop and popularize, it is essential to provide users with a comfortable human-machine interface.

5. Support various high-performance CPUs

In the next-generation digital TV decoder solution, a powerful CPU should be used to handle the interactive application services of the emerging digital TV API. The decoder used should have a convenient interface so that it can be easily used with those widely used. CPU to connect. Through the open CPU interface, manufacturers can choose the corresponding CPU according to different target products to realize the design of the set-top box. For basic function type set-top boxes used only for displaying TV programs, you can choose an inexpensive low-performance CPU; for data service application type set-top boxes, you should choose a very powerful CPU.

6. Industry standard host bus interface

The digital TV decoder must be designed around a high-performance bus (such as a PCI interface bus). In the past few years, due to the continuous development of PC technology, the PCI bus has developed into a very stable and mature interface bus. In the design, it is easy to use a variety of commonly used PCI peripheral devices, including Super I / O, P1394, USB, V.90 modem, and Super 3D graphics.

The structure of the digital TV decoder based on the PCI bus adopts a modular structure, which can be easily upgraded according to different target markets. For example, to connect a camera, you can add a P1394 or USB interface to a digital TV set-top box; to provide real-time gaming services on a wide-screen digital TV, you can add a PCI-based 3D graphics component. As long as an inexpensive PCI bus V.90 modem is simply added, two-way transmission capability can also be obtained to achieve more advanced data services. In addition, the PCI bus structure also makes the CPU upgrade very simple. The CPU based on the PCI bus can be easily replaced with a more powerful CPU without changing the basic design of the set-top box. Consumer electronics manufacturers simply need to make some improvements in software or hardware, and can use different performance CPUs and memories to develop a series of set-top box products from low-end to high-end. The use of PCI interface can greatly shorten and simplify the development of software and hardware, and accelerate the process of bringing digital TV products to market.

7. Fusion of PC and digital TV

The three companies Intel, Microsoft and Compaq have been working on introducing the PC platform into the field of digital TV technology. The PC industry has a huge market with annual shipments of 100 million units. This provides profitable opportunities for manufacturers of digital TV decoder chips.

The structure of the decoder should provide convenience for the design of the PC / DTV option card in order to expand the coverage of the digital TV. Because the PC / DTV board is easy to design and upgrade, the digital TV decoder chip based on the PCI bus will have a great advantage in breaking into the PC market.

Figure 2 is a set-top box solution using the next-generation digital TV decoder circuit design. The decoder integrates super graphics capabilities, can provide a variety of improved data services, and is equipped with a standard PCI bus interface, you can choose to use a variety of different high-performance CPU, while also using an integrated memory structure (unified memory ), Which constitutes an advanced digital TV reception program.

Demand for open digital TV reference platform

Digital TV technology is very complex, and designing the next-generation decoder chip solves only part of the problems facing manufacturers. Unlike traditional analog TV solutions, digital TV software is an important part due to interactive data services. With the emergence of digital TV APIs and new applications, software development has become a major task in digital TV design. Integrated circuit manufacturers must provide a reference platform around digital TV decoder chips to help consumer electronics manufacturers better design. System-level solutions and reference platforms based on the integration of next-generation decoder structures will greatly shorten time to market. While developing digital TV products, the reference platform will accelerate the software development process.

The reference platform also provides an easy-to-use platform for third-party software developers to develop digital TV application software. Without such a platform, software developers can only wait for consumer electronics manufacturers to produce set-top boxes before they can develop their own. With the help of a reference platform, software manufacturers can develop their applications while manufacturers design set-top boxes. An easily accessible, low-cost reference platform helps innovation by third-party developers, and it is the foundation for broadening digital TV applications.

The reference platform with an open structure provides a tool for software, hardware and peripheral equipment inspection, debugging and verification in a real system environment. The device driver, real-time operating system API and application software provided by the reference environment can be used to demonstrate the functions of the digital TV to ensure the high quality of the product. The shortened product design time for manufacturers and software developers makes it possible to significantly reduce costs and get to market faster.

in conclusion

The development of digital TV in the future may provide consumers with many exciting products, which will bring more than the data services we already have or can imagine now. Over time, digital TV is likely to evolve into a multimedia network center in the home of ordinary consumers? ? It can handle DVD, audio, video games and other emerging application services.

In the future, consumer electronics manufacturers will face a variety of digital TV decoder solutions from different chip manufacturing companies. Choosing the correct integrated circuit decoder solution and reference platform for the next generation of digital TV products is one of the key factors for whether the product can win the final market.

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