Abstract: From the development history of set-top boxes, it can be seen that set-top boxes have different functions and functions in different periods. In the process of the rise and maturity of IPTV services, there is also a new demand for set-top boxes. This paper first introduces the current IPTV set-top box technology solutions and analyzes and compares them at the same time. Then it introduces the progress of IPTV set-top box standards and the views on the future development of IPTV set-top boxes. This paper has a certain reference for the development of IPTV set-top box equipment.
1. The development history of set-top boxes
The set top box (STB) originated in the early 1990s, when it was mainly a descrambling device designed by European and American cable television stations to solve the problem of cable TV viewing fees. The set-top box as a digital TV (DTV) auxiliary device began with the trial broadcasting of digital TV and high-definition digital television (HDTV) in Europe and the United States in the late 1990s. Its main role is to enable users to watch digital TV programs and high-definition digital TV programs on the original analog TV, that is, to provide digital/analog signal conversion functions. These set-top boxes are usually called digital TV set-top boxes. The digital TV set-top box has network environment features and conditional access functions. The so-called network environment feature refers to the difference in set-top boxes used in different television broadcast networks. According to the three digital TV transmission systems defined by ETSI, there are: digital TV set-top box DVB-C for receiving cable TV, digital TV set-top box DVB-S for receiving digital satellite TV, digital TV set-top box for receiving terrestrial broadcast TV DVB-T III Types.
In recent years, with the development of broadband networks, Internet applications have become more and more widespread, and people have begun to use the Internet to watch TV. In particular, the IPTV booming development has driven the terminal market to be active. Telecom equipment manufacturers have invested in R&D and production of set-top boxes. The original digital TV set-top box manufacturers are also testing two-way IP set-top boxes. The set-top box has been developed from a single descrambling or digital/analog-dedicated set-top box to support multiple access methods and IP. It has multiple codec and graphics browser functions, and can support video on demand, including digital TV. IPTV set-top boxes for mobile TV, web browsing, information services, distance learning and medical, interactive games and other business functions. Future IPTV set-top boxes will be widely used as a home digital platform for the expanding field of interactive multimedia digital content services.
2. Technical requirements for IPTV set-top boxes
The IPTV service is a brand-new business model. It brings consumers a network of information, entertainment, learning and shopping. Personal computers, set-top boxes + TV sets or 3G mobile phones can all be used as terminals for IPTV services. From the perspective of suiting the consumption habits and comfort of the majority of users, the set-top box + TV set should be the mainstream terminal of IPTV in the future. When it comes to the technical requirements of IPTV set-top boxes, here are two main considerations: one is to meet the needs of the business, and the other is the demand for user experience.
IPTV can provide services such as live TV, video on demand, time-shifted TV, visual services, information services, web browsing, interactive games, and future scalable services. The main business characteristics of IPTV are reflected in the interactive multimedia retrieval and playback format. Interaction requires the network to have two-way capabilities, and retrieval requires two-way information interaction. Broadcast control also needs to interact; playback requires sufficient access bandwidth and media transmission protocol; multimedia requires audio and video encoding and decoding capabilities. Therefore, in order to implement the IPTV service application, the IPTV set-top box is required to support the receiving of the live broadcast television program, and perform basic business functions such as video on demand and time shift on-demand, as well as Internet browsing and information services, electronic program guide (EPG) and program retrieval. And extended features such as interactive games and software online upgrades. The set-top box equipment as the IPTV service terminal should have an open system structure to adapt to the continuously upgraded and expanded service requirements; fully consider the network environment and protocol factors, and require it to have no less than two uplink network interfaces and support multiple accesses. Authentication protocol and IP; requires audio and video media codec, as well as business applications and management functions. In short, from an operational perspective, IPTV set-top boxes require open service capabilities to meet evolving business needs.
Considering the needs of the user experience, the change brought by the IPTV service is to transfer the study experience of the traditional Internet PC terminal to watch the streaming video to the living room, change the forward leaning posture into the backward sitting posture, and change the keyboard operation to the remote control operation. These changes require that the design of the IPTV set-top box should fully consider the user community that is accustomed to operating the TV set, and should try to keep the operation simple, cost-effective and durable. According to the different consumption needs of users. The set-top box should be designed in different grades of high, medium and low to meet the consumer groups of all levels.
IPTV set-top boxes must meet the above requirements in the design process and require a series of key technologies, including audio and video codec technology, graphics and image display technology, media streaming/control technology (protocol), middleware technology, and embedded. System and various interface technologies.
3. Technical solution for IPTV set-top box
Early set-top boxes could only provide video services, and the focus of technology was mainly on the video part. The ultimate goal of the IPTV service is to achieve the convergence of video, voice and data, and provide three-network convergence services through the IPTV set-top box. Because IPTV set-top boxes can serve as a link for simultaneously providing video, voice and data convergence services, combined with broadband access and wireless networks, a truly networked home environment can be created.
The application process of the IPTV set-top box is generally that the service content is accessed to the set-top box through the broadband network, and the video content is requested from the broadband network by using the set-top box remote controller or the remote control keyboard, and the broadband network transmits the required video signal to the user end, and is decoded on the television after the set-top box is decoded. Output. Implement video on demand or web browsing.
There are roughly three grades of set-top box products that can support IPTV services, namely basic, enhanced and super-strong. The so-called basic type means that the set-top box can support the basic service of IPTV, provide an electronic program list, realize the playback of the network television program, and can perform basic play control. In addition to basic features, the enhanced set-top box provides Internet browsing, visual services, text messaging and simple gaming. The super high-end set-top box is equivalent to a home digital entertainment center, which can not only provide basic services and extended services of IPTV, but also realize high value-added functions such as video interactive games and personal video storage.
3.1 Hardware structure of IPTV set-top box
The set-top box device is composed of two parts: hardware and software. The system platforms of different grades of set-top boxes are different, and the software architecture is different, so that the functions they implement are also different. There are basically three types of platforms in the hardware structure, namely based on a dedicated chip architecture, a multimedia digital signal processor (DSP) architecture and a platform based on the X86 architecture. The software structure mostly adopts a hierarchical and modular structure, and also adopts a middleware structure.
The hardware structure of the set-top box consists of a core control unit, a media processing unit, and various types of interfaces, as shown in Figure 1. The core control unit generally uses an embedded system processor chip that can run a real-time operating system. The media processing unit generally selects an ASIC dedicated decoding chip or a digital signal processor according to the cost of the set top box, and is also implemented by software decoding. The IPTV set-top box interface is much richer than other TV set-top boxes. The network-side interface can be configured as a high-speed Ethernet interface, an ADSL interface or a wireless LAN interface, or even an EPON or cable interface, depending on the network access mode. The media player interface is basically equipped with a composite audio and video terminal and an S terminal. The higher configuration can have YpbPr, YCbCr and digital audio output interfaces. The control interface refers to the interface that the user operates and controls the set-top box. Generally, the infrared remote control is mainly used, and the infrared remote control keyboard or WiFi technology is also used. In addition to the interfaces necessary for the above basic service applications, other expansion interfaces such as a USB interface, a serial interface, a Z interface, and a smart card interface can be configured according to business needs.
As can be seen from Figure 1, the core components of the IPTV set-top box are the CPU and the codec. The strength of the set-top box function is directly related to the selection of core components of different grades. The currently available set-top box products are summarized based on the following three structures:
Figure 1 Hardware structure of IPTV set-top box
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(1) Structure based on dedicated chip (SOC+ASIC)
In addition to the processor, the dedicated video image processing chip integrates some intelligent modules, such as audio and video input and output, and some integrate image compression and hardware acceleration modules. In essence, the dedicated video compression chip and the general-purpose video processing chip belong to the SOC (system on chip). The difference is that the former has a fixed compression module, a fixed processing method and a fixed micro-code, and the latter requires product developers to develop. Video compression algorithm program.
The traditional ASIC/SOC-based set-top box, due to its implementation of the full hardware chip, makes it impossible for operators to implement effective software upgrades, and its network adaptability also has major problems. However, due to the low cost of the set-top box based on this structure, in the initial stage of the IPTV service, the service provider generally provides the set-top box to the user for free, and the set-top box with the dedicated chip structure can save the service operator under the premise of ensuring the basic service. Operating expenses will undoubtedly play a very good role in business promotion.
(2) Structure based on multimedia digital signal processor
The IPTV set-top box based on multimedia processor technology uses a high-performance digital signal processor and an embedded system chip as a hardware platform. DSP is mainly used for video and audio decoding processing, embedded real-time operating system chip is used to control the processing of data from various interfaces and computing requirements. The multimedia digital processor architecture can easily implement MPEG-2/4 video and audio processing, H.264 video processing, and other encoding and decoding standards for IPTV. The primary indicator for evaluating an IPTV set-top box is its ability to support media formats. Since the media format for the IPTV service has not yet been unified, and the operators are also in the test selection stage, the set-top box based on the multimedia digital signal processor structure can flexibly write different codes or directly form a double decoding form.
Embedded systems are a combination of technologies such as computers, communications, semiconductors, microelectronics, voice/image/data transmission processing, and specific application objects. In general, embedded systems consist of embedded chips, embedded software, embedded operating systems, and embedded system development tools. Embedded chips include embedded microprocessors, embedded microcontrollers, embedded digital signal processors, and embedded system-on-chip. With the rapid development of RISC (Reduced Instruction Set Computer) technology and microelectronics technology, the function of embedded chips is more The stronger the volume, the smaller the volume.
The embedded real-time operating system is different from the desktop computer operating system in that it is not installed in the hard disk but is solidified in the memory. The embedded operating system is compact in structure, relatively simple in function, and low in resource overhead. Currently, there are three main types: Windows CE, Linux, and VxWork, among which the first two are widely used. Windows CE is mainly used on high-end set-top boxes, which brings convenience to the networking of set-top boxes and PCs. But the cost is high. For mid-range set-top boxes, it is more reasonable to use the Linux operating system. According to a report released by market research firm Strategy Analytics. In the global set-top box market, the Linux operating platform has become the main choice for IPTV set-top boxes. Because the Linux platform can support many advanced features, such as video and IP transmission, and is very economical, no license fee is required.
(3) X86-based structure
Compared with the RISC-based CPU-based embedded system, the embedded system based on the X86 architecture CPU has the following advantages: First, it can encode and decode files of different formats, such as MPEG-2, MPEG-4, WMA, etc., based on this Multimedia audio and video equipment on the embedded platform can handle a wide variety of sources. Secondly, the Windows CE operating system has a complete set of integrated multimedia functions and extremely rich applications, making the development of IPTV set-top boxes shorter, suitable for the development of advanced IPTV set-top boxes. The inherent desktop compatibility of the operating system allows set-top box developers to easily extend the capabilities of IP set-top boxes with a large number of applications for Windows XP.
The X86-based set-top box has a complete application software because of the embedded Windows CE real-time operating system, which has low maintenance cost and can be easily shared with PC resources. Due to the high development cost of this set-top box product, although it is powerful, it can compete with PC, but it can only face high-end consumer groups. At least it will not be very attractive to the general consumers at the beginning.
3.2 Software structure of IPTV set-top box
As a client product, IPTV set-top box requires the cooperation of software systems in addition to a good hardware platform to realize IPTV service functions. The software of the set-top box mostly adopts a layered structure, which is generally divided into three layers: an application layer, an intermediate interpretation layer and a resource layer. Each layer includes a plurality of programs and programming interfaces, as shown in FIG. 2 .
Figure 2 Software structure of IPTV set-top box
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Figure 2 divides the three-layer structure of the set-top box software. The resource layer software includes a real-time operating system and a set-top box hardware driver, which is mainly used to complete the operation of the hardware device. The main function of the interpretation layer is to translate the set-top box application into instructions that the CPU can recognize, and to mobilize the hardware device to complete the corresponding operation. The application layer can be divided into a built-in application and a download application to implement business applications such as TV playback, video on demand, EPG, DRM (Digital Rights Management), and game download.
Different set-top box manufacturers have different design concepts for IPTV set-top box software. In the design of the IPTV service, the business process development software defined between the service platform and the set top box is used, and the general service software or middleware located between the underlying system resource and the business application is also utilized. But the general trend is to use business application software and the underlying hardware and operating system software to isolate, the use of middleware is a good choice. The middleware separates the application in the set-top box from the underlying system components, making the development of the application independent of the hardware platform. It provides a range of open application programming interfaces (APIs) for different operating systems and hardware environments. The use of middleware technology can reduce the difficulty of application development and improve research and development efficiency.
4. IPTV set-top box standardization process and future development direction
As an emerging broadband network service, IPTV is increasingly valued by the industry. In particular, products like home-set digital platforms like set-top boxes are more sought after by telecom equipment manufacturers, TV equipment manufacturers, and manufacturers of computer and home appliances. Due to the different understandings of IPTV services between industries and different product design concepts, the functions, performance and application environment requirements of IPTV set-top boxes vary widely, and they are not universal. This state is extremely unfavorable to the development of the industry, and this may lead to the collapse of a new business. Therefore, China Communications Standards Association established the IPTV service special working group in August 2005, focusing on the IPTV service series standards, including the IPTV set-top box technical requirements. In this standard, specific technical requirements are given for the service capabilities, functional requirements, hardware systems, software systems, management functional requirements, performance requirements, security and application environments of IPTV set-top boxes.
In the research process of IPTV set-top box technology standards, the functions and hardware and software structures of the existing IPTV set-top boxes are fully referenced. For the current controversial codec format and whether or not to adopt middleware technology, the standard does not stipulate the only way, but adopts Specifying multiple options leaves manufacturers with more choices. However, no matter which option is selected, the functions and interfaces are required to be consistent, so that this standard has practical guiding significance for the development, manufacture, detection and application of all IPTV set-top boxes.
At present, the technical standards for IPTV set-top boxes have been carried out to the stage of soliciting comments, which will be further improved and revised after listening to the opinions of various experts in relevant industries. at the same time. The digital TV middleware technology standards related to IPTV services and set-top boxes and the audio and video codec standards developed by China itself are also being formulated and improved. It is expected that a complete set of IPTV industry standards will emerge soon. It is used to guide the smooth development of IPTV services.
With the systematic and industrialized development of IPTV services, the IPTV set-top box industry will continue to grow. The development of future set-top boxes may be branched. On the one hand, it may be developed in the direction of consumer electronics products, and the set-top box functions will be integrated into the TV set. The functionality provided by the TV set-top box can cover the general functions of the IPTV service, including live TV programming, video on demand, information reception and downloading, and simple gaming functions. On the other hand, IPTV set-top boxes may be developed in the direction of home digital platforms, with powerful functions and rich peripheral interfaces. In addition to supporting basic IPTV services, they can also support videophone services, interactive game services, Internet shopping, and interactive teaching. Such as interactive, real-time business. In addition, with the development of next-generation networks and the convergence of telecommunications, television, and Internet triple-play, IPTV set-top boxes will also have dual-mode set-top boxes. With the further development of microelectronics technology, dual decoder chips and large-capacity memory chips will continue to emerge, which will bring more functions to the set-top box. There will be more and more set-top boxes with dual decoding capabilities and local personal video storage capabilities. In short, with the advancement of science and the development of technology, IPTV set-top box products will become more mature and more powerful. In the near future, people will be able to experience the IPTV service through the set-top box, and they can enjoy the world, entertainment and shopping, and enjoy the time-space enjoyment of thousands of miles.
5, the conclusion
Looking forward to the IPTV set-top box, the prospects are boundless, but the road under our feet is still very rugged, and there are many difficulties in front of us. The first is the choice of audio and video codec technology. Currently, the audio and video codec standards for IPTV services mainly include MPEG-4 and H.264 protocols. Both of these standards have very demanding patent charging conditions. Countries, whether it is for IPTV service operators or set-top box equipment manufacturers are a very substantial investment. The audio and video codec standards developed by China itself have not yet reached the mature commercial stage for IPTV services. How to choose a codec standard is a problem that needs to be studied. Followed by the protocol encapsulation problem. Streaming of IPTV should be based on common open standards. Therefore, most of the IPTV solutions that use MPEG-4 and H.264 for IP transmission use Stream DATA/TS/UDP/IP, Stream DATA/TS/RTP/UDP/IP, Stream DATA/RTP/UDP/IP. . The first two modes carry information rich, including EPG information, but the package is small and wastes bandwidth. The third method is more suitable for the characteristics of the IP network, but the carrying information is not as good as the first two. There are also many issues such as the choice of middleware technology, information security and digital copyright protection, graphics and image display, etc., all need to do careful and meticulous work in the development of set-top boxes. In combination with the development trend of IPTV services, the selection of technical solutions that are consistent with and slightly ahead of the business, adopting an open architecture, providing the ability to smoothly upgrade services, can ensure that the products developed meet the needs of IPTV set-top boxes.
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1. The development history of set-top boxes
The set top box (STB) originated in the early 1990s, when it was mainly a descrambling device designed by European and American cable television stations to solve the problem of cable TV viewing fees. The set-top box as a digital TV (DTV) auxiliary device began with the trial broadcasting of digital TV and high-definition digital television (HDTV) in Europe and the United States in the late 1990s. Its main role is to enable users to watch digital TV programs and high-definition digital TV programs on the original analog TV, that is, to provide digital/analog signal conversion functions. These set-top boxes are usually called digital TV set-top boxes. The digital TV set-top box has network environment features and conditional access functions. The so-called network environment feature refers to the difference in set-top boxes used in different television broadcast networks. According to the three digital TV transmission systems defined by ETSI, there are: digital TV set-top box DVB-C for receiving cable TV, digital TV set-top box DVB-S for receiving digital satellite TV, digital TV set-top box for receiving terrestrial broadcast TV DVB-T III Types.
In recent years, with the development of broadband networks, Internet applications have become more and more widespread, and people have begun to use the Internet to watch TV. In particular, the IPTV booming development has driven the terminal market to be active. Telecom equipment manufacturers have invested in R&D and production of set-top boxes. The original digital TV set-top box manufacturers are also testing two-way IP set-top boxes. The set-top box has been developed from a single descrambling or digital/analog-dedicated set-top box to support multiple access methods and IP. It has multiple codec and graphics browser functions, and can support video on demand, including digital TV. IPTV set-top boxes for mobile TV, web browsing, information services, distance learning and medical, interactive games and other business functions. Future IPTV set-top boxes will be widely used as a home digital platform for the expanding field of interactive multimedia digital content services.
2. Technical requirements for IPTV set-top boxes
The IPTV service is a brand-new business model. It brings consumers a network of information, entertainment, learning and shopping. Personal computers, set-top boxes + TV sets or 3G mobile phones can all be used as terminals for IPTV services. From the perspective of suiting the consumption habits and comfort of the majority of users, the set-top box + TV set should be the mainstream terminal of IPTV in the future. When it comes to the technical requirements of IPTV set-top boxes, here are two main considerations: one is to meet the needs of the business, and the other is the demand for user experience.
IPTV can provide services such as live TV, video on demand, time-shifted TV, visual services, information services, web browsing, interactive games, and future scalable services. The main business characteristics of IPTV are reflected in the interactive multimedia retrieval and playback format. Interaction requires the network to have two-way capabilities, and retrieval requires two-way information interaction. Broadcast control also needs to interact; playback requires sufficient access bandwidth and media transmission protocol; multimedia requires audio and video encoding and decoding capabilities. Therefore, in order to implement the IPTV service application, the IPTV set-top box is required to support the receiving of the live broadcast television program, and perform basic business functions such as video on demand and time shift on-demand, as well as Internet browsing and information services, electronic program guide (EPG) and program retrieval. And extended features such as interactive games and software online upgrades. The set-top box equipment as the IPTV service terminal should have an open system structure to adapt to the continuously upgraded and expanded service requirements; fully consider the network environment and protocol factors, and require it to have no less than two uplink network interfaces and support multiple accesses. Authentication protocol and IP; requires audio and video media codec, as well as business applications and management functions. In short, from an operational perspective, IPTV set-top boxes require open service capabilities to meet evolving business needs.
Considering the needs of the user experience, the change brought by the IPTV service is to transfer the study experience of the traditional Internet PC terminal to watch the streaming video to the living room, change the forward leaning posture into the backward sitting posture, and change the keyboard operation to the remote control operation. These changes require that the design of the IPTV set-top box should fully consider the user community that is accustomed to operating the TV set, and should try to keep the operation simple, cost-effective and durable. According to the different consumption needs of users. The set-top box should be designed in different grades of high, medium and low to meet the consumer groups of all levels.
IPTV set-top boxes must meet the above requirements in the design process and require a series of key technologies, including audio and video codec technology, graphics and image display technology, media streaming/control technology (protocol), middleware technology, and embedded. System and various interface technologies.
3. Technical solution for IPTV set-top box
Early set-top boxes could only provide video services, and the focus of technology was mainly on the video part. The ultimate goal of the IPTV service is to achieve the convergence of video, voice and data, and provide three-network convergence services through the IPTV set-top box. Because IPTV set-top boxes can serve as a link for simultaneously providing video, voice and data convergence services, combined with broadband access and wireless networks, a truly networked home environment can be created.
The application process of the IPTV set-top box is generally that the service content is accessed to the set-top box through the broadband network, and the video content is requested from the broadband network by using the set-top box remote controller or the remote control keyboard, and the broadband network transmits the required video signal to the user end, and is decoded on the television after the set-top box is decoded. Output. Implement video on demand or web browsing.
There are roughly three grades of set-top box products that can support IPTV services, namely basic, enhanced and super-strong. The so-called basic type means that the set-top box can support the basic service of IPTV, provide an electronic program list, realize the playback of the network television program, and can perform basic play control. In addition to basic features, the enhanced set-top box provides Internet browsing, visual services, text messaging and simple gaming. The super high-end set-top box is equivalent to a home digital entertainment center, which can not only provide basic services and extended services of IPTV, but also realize high value-added functions such as video interactive games and personal video storage.
3.1 Hardware structure of IPTV set-top box
The set-top box device is composed of two parts: hardware and software. The system platforms of different grades of set-top boxes are different, and the software architecture is different, so that the functions they implement are also different. There are basically three types of platforms in the hardware structure, namely based on a dedicated chip architecture, a multimedia digital signal processor (DSP) architecture and a platform based on the X86 architecture. The software structure mostly adopts a hierarchical and modular structure, and also adopts a middleware structure.
The hardware structure of the set-top box consists of a core control unit, a media processing unit, and various types of interfaces, as shown in Figure 1. The core control unit generally uses an embedded system processor chip that can run a real-time operating system. The media processing unit generally selects an ASIC dedicated decoding chip or a digital signal processor according to the cost of the set top box, and is also implemented by software decoding. The IPTV set-top box interface is much richer than other TV set-top boxes. The network-side interface can be configured as a high-speed Ethernet interface, an ADSL interface or a wireless LAN interface, or even an EPON or cable interface, depending on the network access mode. The media player interface is basically equipped with a composite audio and video terminal and an S terminal. The higher configuration can have YpbPr, YCbCr and digital audio output interfaces. The control interface refers to the interface that the user operates and controls the set-top box. Generally, the infrared remote control is mainly used, and the infrared remote control keyboard or WiFi technology is also used. In addition to the interfaces necessary for the above basic service applications, other expansion interfaces such as a USB interface, a serial interface, a Z interface, and a smart card interface can be configured according to business needs.
As can be seen from Figure 1, the core components of the IPTV set-top box are the CPU and the codec. The strength of the set-top box function is directly related to the selection of core components of different grades. The currently available set-top box products are summarized based on the following three structures:
Figure 1 Hardware structure of IPTV set-top box
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(1) Structure based on dedicated chip (SOC+ASIC)
In addition to the processor, the dedicated video image processing chip integrates some intelligent modules, such as audio and video input and output, and some integrate image compression and hardware acceleration modules. In essence, the dedicated video compression chip and the general-purpose video processing chip belong to the SOC (system on chip). The difference is that the former has a fixed compression module, a fixed processing method and a fixed micro-code, and the latter requires product developers to develop. Video compression algorithm program.
The traditional ASIC/SOC-based set-top box, due to its implementation of the full hardware chip, makes it impossible for operators to implement effective software upgrades, and its network adaptability also has major problems. However, due to the low cost of the set-top box based on this structure, in the initial stage of the IPTV service, the service provider generally provides the set-top box to the user for free, and the set-top box with the dedicated chip structure can save the service operator under the premise of ensuring the basic service. Operating expenses will undoubtedly play a very good role in business promotion.
(2) Structure based on multimedia digital signal processor
The IPTV set-top box based on multimedia processor technology uses a high-performance digital signal processor and an embedded system chip as a hardware platform. DSP is mainly used for video and audio decoding processing, embedded real-time operating system chip is used to control the processing of data from various interfaces and computing requirements. The multimedia digital processor architecture can easily implement MPEG-2/4 video and audio processing, H.264 video processing, and other encoding and decoding standards for IPTV. The primary indicator for evaluating an IPTV set-top box is its ability to support media formats. Since the media format for the IPTV service has not yet been unified, and the operators are also in the test selection stage, the set-top box based on the multimedia digital signal processor structure can flexibly write different codes or directly form a double decoding form.
Embedded systems are a combination of technologies such as computers, communications, semiconductors, microelectronics, voice/image/data transmission processing, and specific application objects. In general, embedded systems consist of embedded chips, embedded software, embedded operating systems, and embedded system development tools. Embedded chips include embedded microprocessors, embedded microcontrollers, embedded digital signal processors, and embedded system-on-chip. With the rapid development of RISC (Reduced Instruction Set Computer) technology and microelectronics technology, the function of embedded chips is more The stronger the volume, the smaller the volume.
The embedded real-time operating system is different from the desktop computer operating system in that it is not installed in the hard disk but is solidified in the memory. The embedded operating system is compact in structure, relatively simple in function, and low in resource overhead. Currently, there are three main types: Windows CE, Linux, and VxWork, among which the first two are widely used. Windows CE is mainly used on high-end set-top boxes, which brings convenience to the networking of set-top boxes and PCs. But the cost is high. For mid-range set-top boxes, it is more reasonable to use the Linux operating system. According to a report released by market research firm Strategy Analytics. In the global set-top box market, the Linux operating platform has become the main choice for IPTV set-top boxes. Because the Linux platform can support many advanced features, such as video and IP transmission, and is very economical, no license fee is required.
(3) X86-based structure
Compared with the RISC-based CPU-based embedded system, the embedded system based on the X86 architecture CPU has the following advantages: First, it can encode and decode files of different formats, such as MPEG-2, MPEG-4, WMA, etc., based on this Multimedia audio and video equipment on the embedded platform can handle a wide variety of sources. Secondly, the Windows CE operating system has a complete set of integrated multimedia functions and extremely rich applications, making the development of IPTV set-top boxes shorter, suitable for the development of advanced IPTV set-top boxes. The inherent desktop compatibility of the operating system allows set-top box developers to easily extend the capabilities of IP set-top boxes with a large number of applications for Windows XP.
The X86-based set-top box has a complete application software because of the embedded Windows CE real-time operating system, which has low maintenance cost and can be easily shared with PC resources. Due to the high development cost of this set-top box product, although it is powerful, it can compete with PC, but it can only face high-end consumer groups. At least it will not be very attractive to the general consumers at the beginning.
3.2 Software structure of IPTV set-top box
As a client product, IPTV set-top box requires the cooperation of software systems in addition to a good hardware platform to realize IPTV service functions. The software of the set-top box mostly adopts a layered structure, which is generally divided into three layers: an application layer, an intermediate interpretation layer and a resource layer. Each layer includes a plurality of programs and programming interfaces, as shown in FIG. 2 .
Figure 2 Software structure of IPTV set-top box
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Figure 2 divides the three-layer structure of the set-top box software. The resource layer software includes a real-time operating system and a set-top box hardware driver, which is mainly used to complete the operation of the hardware device. The main function of the interpretation layer is to translate the set-top box application into instructions that the CPU can recognize, and to mobilize the hardware device to complete the corresponding operation. The application layer can be divided into a built-in application and a download application to implement business applications such as TV playback, video on demand, EPG, DRM (Digital Rights Management), and game download.
Different set-top box manufacturers have different design concepts for IPTV set-top box software. In the design of the IPTV service, the business process development software defined between the service platform and the set top box is used, and the general service software or middleware located between the underlying system resource and the business application is also utilized. But the general trend is to use business application software and the underlying hardware and operating system software to isolate, the use of middleware is a good choice. The middleware separates the application in the set-top box from the underlying system components, making the development of the application independent of the hardware platform. It provides a range of open application programming interfaces (APIs) for different operating systems and hardware environments. The use of middleware technology can reduce the difficulty of application development and improve research and development efficiency.
4. IPTV set-top box standardization process and future development direction
As an emerging broadband network service, IPTV is increasingly valued by the industry. In particular, products like home-set digital platforms like set-top boxes are more sought after by telecom equipment manufacturers, TV equipment manufacturers, and manufacturers of computer and home appliances. Due to the different understandings of IPTV services between industries and different product design concepts, the functions, performance and application environment requirements of IPTV set-top boxes vary widely, and they are not universal. This state is extremely unfavorable to the development of the industry, and this may lead to the collapse of a new business. Therefore, China Communications Standards Association established the IPTV service special working group in August 2005, focusing on the IPTV service series standards, including the IPTV set-top box technical requirements. In this standard, specific technical requirements are given for the service capabilities, functional requirements, hardware systems, software systems, management functional requirements, performance requirements, security and application environments of IPTV set-top boxes.
In the research process of IPTV set-top box technology standards, the functions and hardware and software structures of the existing IPTV set-top boxes are fully referenced. For the current controversial codec format and whether or not to adopt middleware technology, the standard does not stipulate the only way, but adopts Specifying multiple options leaves manufacturers with more choices. However, no matter which option is selected, the functions and interfaces are required to be consistent, so that this standard has practical guiding significance for the development, manufacture, detection and application of all IPTV set-top boxes.
At present, the technical standards for IPTV set-top boxes have been carried out to the stage of soliciting comments, which will be further improved and revised after listening to the opinions of various experts in relevant industries. at the same time. The digital TV middleware technology standards related to IPTV services and set-top boxes and the audio and video codec standards developed by China itself are also being formulated and improved. It is expected that a complete set of IPTV industry standards will emerge soon. It is used to guide the smooth development of IPTV services.
With the systematic and industrialized development of IPTV services, the IPTV set-top box industry will continue to grow. The development of future set-top boxes may be branched. On the one hand, it may be developed in the direction of consumer electronics products, and the set-top box functions will be integrated into the TV set. The functionality provided by the TV set-top box can cover the general functions of the IPTV service, including live TV programming, video on demand, information reception and downloading, and simple gaming functions. On the other hand, IPTV set-top boxes may be developed in the direction of home digital platforms, with powerful functions and rich peripheral interfaces. In addition to supporting basic IPTV services, they can also support videophone services, interactive game services, Internet shopping, and interactive teaching. Such as interactive, real-time business. In addition, with the development of next-generation networks and the convergence of telecommunications, television, and Internet triple-play, IPTV set-top boxes will also have dual-mode set-top boxes. With the further development of microelectronics technology, dual decoder chips and large-capacity memory chips will continue to emerge, which will bring more functions to the set-top box. There will be more and more set-top boxes with dual decoding capabilities and local personal video storage capabilities. In short, with the advancement of science and the development of technology, IPTV set-top box products will become more mature and more powerful. In the near future, people will be able to experience the IPTV service through the set-top box, and they can enjoy the world, entertainment and shopping, and enjoy the time-space enjoyment of thousands of miles.
5, the conclusion
Looking forward to the IPTV set-top box, the prospects are boundless, but the road under our feet is still very rugged, and there are many difficulties in front of us. The first is the choice of audio and video codec technology. Currently, the audio and video codec standards for IPTV services mainly include MPEG-4 and H.264 protocols. Both of these standards have very demanding patent charging conditions. Countries, whether it is for IPTV service operators or set-top box equipment manufacturers are a very substantial investment. The audio and video codec standards developed by China itself have not yet reached the mature commercial stage for IPTV services. How to choose a codec standard is a problem that needs to be studied. Followed by the protocol encapsulation problem. Streaming of IPTV should be based on common open standards. Therefore, most of the IPTV solutions that use MPEG-4 and H.264 for IP transmission use Stream DATA/TS/UDP/IP, Stream DATA/TS/RTP/UDP/IP, Stream DATA/RTP/UDP/IP. . The first two modes carry information rich, including EPG information, but the package is small and wastes bandwidth. The third method is more suitable for the characteristics of the IP network, but the carrying information is not as good as the first two. There are also many issues such as the choice of middleware technology, information security and digital copyright protection, graphics and image display, etc., all need to do careful and meticulous work in the development of set-top boxes. In combination with the development trend of IPTV services, the selection of technical solutions that are consistent with and slightly ahead of the business, adopting an open architecture, providing the ability to smoothly upgrade services, can ensure that the products developed meet the needs of IPTV set-top boxes.
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