Technical Analysis of Digital TV HbbTV and GoogleTV Platform
1 Introduction
Since digital TV was put into operation in 1995, the middleware business platform has been the subject of research and discussion. Digital TV operators represented by Europe have always believed that the development of digital TV value-added services is the ultimate goal of their development. Digital TV requires middleware platforms, and requires limited compatibility and walled management of Internet applications (Walled Garden) . This is a view from "TV" to "Internet (or computer)". The point of view represented by Americans is that a digital TV receiving device is an Internet terminal that is embedded in browser software and runs web browsing to achieve digital TV entertainment. This is a view from "Internet (or computer)" to "TV". It can be seen from this that Europeans are considering how to develop value-added services and gain revenue from the operation of digital TV; and Americans are more actively seeking to interconnect home devices to let the rich content of the Internet enter the family's living room terminal.
Different ideas produce different technical routes. Therefore, the middleware platform standard-MHP (Media Home Platform)-with standardized middleware platform architecture, access protocol and application development as the core was born from Europe. The efforts of Americans to embed the Internet in digital TV set-top boxes have never been interrupted. The ATVEF (Advanced Television Enhancement Forum) in the United States released the interactive application specification based on Internet HTML as early as 1999. Microsoft has launched WebTV since 1998, and until the Mediaroom in recent years, it has spent huge financial and material resources for the Microsoft operating system to enter consumer electronics. People in the industry may not forget the "Venus" plan. The United States has also produced a well-known digital TV browser technology company-Liberate. Various middleware platforms aiming at value-added services and different middleware specifications based on MHP (such as OCAP of the American Cable TV Alliance, DTVM of Chinese standards, ARIB in Japan, Ginga-J in Brazil, etc.), as well as many middleware The software business platform plays a role in the operation of different digital TV operators around the world; but the effort to move the Internet to TV is very difficult: the ATVEF standard is basically forgotten, Microsoft ’s WebTV platform and Venus plan Without dying, Liberate also declared bankruptcy long ago. In 2006, Apple launched AppleTV. Its beautiful design and good user experience used to be loved by many people. However, the real market effect is not ideal. Until now, there has not been a commercially significant market deployment.
However, the continuous development of Internet technology and network broadband, and the enrichment of information and video content, especially the concepts and systems that have emerged in recent years, such as social networks, cloud computing, and mobile Internet, have made the relationship between "TV" and "Internet". Integration has become an irresistible trend. However, Europeans and Americans have different understandings of how the two meet. The European digital TV industry has launched a dual-mode business system based on a middleware platform compatible with the Internet (broadband)-HbbTV; Americans continue to work hard on the Internet browser architecture. On the basis of the success of their Android system in the mobile field (mobile phone), Google has pushed it into the field of digital TV and formed GoogleTV.
Currently, there is a view that due to the free open source code, GoogleTV will quickly replace the middleware system and become a unified business platform. This article attempts to explain the development prospects of these two systems from the perspective of technology and operator business needs. The opinions in this article are purely personal, and colleagues in the industry are welcome to criticize and correct them.
2 Technical characteristics of HbbTV and GoogleTV platforms
2.1 Technical introduction of HbbTV platform
HbbTV (Hybrid BroADCast and Broadband Television) evolved and developed on the basis of the MHP standard platform. Strictly speaking, the MHP standard also defines support for Internet protocols (TCP / IP, HTTP, etc.), but most of the specifications of the standard still only apply to download and management of broadcast environments, application lifecycle management, and application programming interfaces. Detailed regulations are made, and the definition of development and management of applications using Internet technologies (HTML, JavaScript, etc.) is not specific. HbbTV makes up for the deficiencies of the MHP middleware platform in these aspects, and carefully regulates the coordination of Internet technology and broadcast channels. The ETSI standards (ETSI 102 796 V1.1.1 2009-12 and ETSI 102 809 V1.1.1 2010-01) submitted by DVB clearly define the technical architecture and application management of HbbTV.
2.1.1 HbbTV platform architecture and functions
HbbTV defines a dual-mode terminal (Hybrid Terminal), which can always be connected to the broadcast TV network when there is no broadband connection, so as to continuously receive audio and video programs and related applications, and can also support broadcast and broadband networks. Connection. The figure below shows the channel sources of HbbTV's services (applications, video, etc.).
Pictured: Channel source of HbbTV service
The following figure depicts the HbbTV system architecture and main functional components. The functions of the main components are briefly explained after the figure.
Pictured: Schematic diagram of the functional components of the dual-mode terminal software system
Through the broadcast TV channel (BroADCast InteRFace), the dual-mode terminal receives AIT data, linear audio and video programs, application data, and stream events. The latter two data are transmitted using the DSM-CC Object Carousel protocol (DSM-CC Object Carousel). Therefore, the DSM-CC Client needs to be embedded in order to receive the data and transmit it to the RunTIme Environment. The operating environment can be regarded as a very abstract component, which executes applications and displays interfaces. Browser (Browser) and application manager (ApplicaTIon Manager) are part of this application running environment. The application manager parses the AIT data to control the life cycle of the application; the browser executes and presents the application.
The processing of linear audio and video content is exactly the same as broadcast TV terminals (or terminals that only support satellite, terrestrial or cable digital TV), and all DVB-related functions are also fully supported (such as channel list, EIT information processing, service selection and Frequency modulation, etc.) is handled by the Broadcast Processing component, and the playback of media content such as audio and video is handled by the Media Player component.
Through a broadband channel (Broadband Interface), dual-mode terminals can be connected to the Internet or other IP networks. It provides a second channel for application data reception to connect to the application provider's server. This connection is used to receive non-linear audio and video content (such as content-on-demand services). The Internet Protocol Processing component contains functions for processing data from IP networks such as the Internet. Through this component, application data is provided to the operating environment, and non-linear audio and video content is transferred to the Media Player, including Parse, present and play in the application.
2.1.2 HbbTV platform business and application model
HbbTV supports two types of applications: 1) radio and television related applications, transmitted through the broadcast television channel; 2) independent of the broadcast television applications, they are not transmitted through the broadcast television channel.
According to the different situations where the application is bound to the broadcast channel (Service) or the network connection, there can be different application models as follows. The following lists from simple to complex:
An application that is only tied to a broadcast channel: when the channel is selected, the application starts; when the channel is switched, the application is terminated;
An application that is bound to multiple channels: when any one of the channels is selected, the application starts; when the channel is switched away, the application is terminated, even if the new channel has this application bound to it;
An application that keeps running when the channel is switched: This application is bound to multiple broadcast channels. When any relevant channel is selected, the application starts; and when switching to a new channel that is also bound to this application, the application does not terminate , Continue to run; only when the selected channel is no longer bound to the application, the application terminates;
Applications that are bound to part of the content of the broadcast channel (for example, to be bound to a single program or advertising content): when the relevant content starts, the application starts; when the relevant content ends, the application terminates;
Applications bound to on-demand content: its control is either consistent with the applications bound to part of the content of the broadcast channel, or it remains valid throughout the on-demand process; applications connected to network operators or service providers: In some deployments, this application connection may be permanent.
The HbbTV standard stipulates in detail the life cycle management of the start and termination of transmission applications through broadcast channels and broadband channels. The following figure shows the process of application life cycle state transition.
Pictured: application life cycle and state transition example
End users can access the interactive application (InteracTIve ApplicaTIon) in the following ways:
By launching the Red Button on the Autostart Application related to a broadcast channel;
Start a Digital Teletext Application through the TEXT Button;
Start a non-broadcast application set by the manufacturer through the Internet TV portal;
By launching a hyperlink on the running application;
By selecting a radio channel, there is a full-screen self-starting application.
2.1.3 Access to broadcast-related self-starting applications
Broadcast-related self-starting applications are usually associated with broadcast channels or programs and events on them. In the first case, the self-starting application should be started immediately; in the second case, there will be the following situations:
A red button is displayed, indicating that an application can be started;
Does not display the user interface;
Display a full screen (such as in audio applications and data applications)
Under normal circumstances, the self-starting application does not display the full screen. When there is a Red Button indicating that there is an application, the user presses the Red Button to display it in full screen; if there is no self-starting application related to broadcasting, holding down the Red Button will make no response.
Pictured: The Red Button indicates that there is an application, press the Red Button to display the application in full screen
The figure above shows the broadcast-related self-launched application launched through the Red Button.
2.1.4 Access to non-broadcast related applications
Non-broadcast-related applications refer to applications that are independent and not transmitted through a broadcast channel. It is generally accessed through a TV portal (TV Portal). The Internet TV portal is an application that provides a starting web page in which non-broadcasting The applications are arranged and displayed so that users can easily browse and access their settings and associated applications (non-broadcast-related applications).
Pictured: the launch of the Internet TV portal
The exit of the application generally adopts the exit button (Exit Button), or the way indicated by the application.
We can see that HbbTV defines a digital TV middleware technology architecture that supports both broadcast services and broadband services, and can support parallel connection with two networks: on the one hand, it can connect to broadcast TV DVB networks (such as DVB -T, DVB-S or DVB-C), through the broadcast TV network, the dual-mode terminal can receive standard broadcast TV programs, which is a linear way of audio and video content, application data and application signaling information; on the other hand The dual-mode terminal can be connected to the Internet (IP network) via broadband and supports two-way communication with the application server. This mode allows the terminal to receive non-linear audio and video content and application data, and also download non-real-time audio and video content.
2.2 Technical introduction of GoogleTV platform
After Google achieved great success in the field of Internet search, it is also striving to enter the field of consumer electronics. The Android platform, which they invested heavily in, started to emerge in the field of mobile phones, and then promoted it to the field of digital TV. Below we focus on introducing and discussing the design concept and technical framework of GoogleTV.
2.2.1 Design concept of GoogleTV platform
Google TV is a conceptual TV platform that integrates computer systems, media playback, and network applications. It is led by Google and is released free of charge. The application of Google TV covers the following areas:
Pictured: GoogleTV design concept
As can be seen from the above figure, in terms of hardware, in addition to the fact that it can be used with a variety of peripheral devices in the actual operating environment, Google TV also has many requirements in terms of specifications; in terms of software, GoogleTV adds its search engine and Android system. In the GoogleTV platform; in application provision, cooperate with the content provider to develop, in order to have a broad application and business development group, and form an Android application store.
2.2.2 Technical architecture of GoogleTV platform
The core software system of GoogleTV is the Android platform, and its architecture is shown in the following schematic diagram.
Pictured: GoogleTV software core Android architecture
Android is a modular and hierarchical architectural design, which is also a common design concept and architectural model of platformized software design. Android has 5 main levels:
1) Application layer
Android will be released together with a series of core application packages, which are written in email client and SMS language. ? Short message programs, calendars, maps, browsers, contact management programs, etc. All applications can use Java
2) Application framework layer
Developers can also access the API framework used by core applications. The application ’s architectural design simplifies the reuse of components; any application can publish its function blocks and any other application can use its published function blocks (in fact, software together is difficult to control not to be Called). Similarly, the application reuse mechanism also allows users to easily replace program components.
Hidden behind each application is a series of services and systems, including;
Extensible views (Views), which can be used to build applications, including lists, grids, text boxes, buttons, etc., and even embeddable web browsers;
Content Provider (Content Provider) allows applications to access the data of another application (such as a contact database), or share their own data;
Resource Manager (Resource Manager) provides access to non-code resources, such as local strings, graphics, and layout files (layout files);
The notification manager (NoTIfication Manager) allows the application to display custom prompts in the status bar;
Activity manager (Activity Manager) is used to manage the application life cycle and provide commonly used navigation back function.
3) Library layer
Android contains some C / C ++ libraries that can be used by different components in the Android system. They provide services to developers through the Android application framework. Here are some core libraries:
System C library: Standard C system function library (libc) inherited from BSD, which is specially optimized for devices based on embedded Linux (Embedded Linux);
Media library: Based on PacketVideo / OpenCORE. The library supports playback and recording of many commonly used audio and video formats, as well as static image files. Supported encoding formats include MPEG-4, H.264, MP3, AAC, AMR, JPG, PNG, etc .;
Display Manager (SuRFace Manager): manages the display subsystem and provides seamless integration of 2D and 3D layers for multiple applications;
Browser engine (LibWebCore): the latest web browser engine, supports Android browser and embeddable web view;
Graphical Engine (SGL): the underlying 2D graphics engine;
3D libraries: based on OpenGL ES 1.0 APIs; the library can use hardware 3D acceleration (if available) or use highly optimized 3D soft acceleration;
Font Engine (FreeType): Bitmap and Vector font display;
SQLite: A powerful and lightweight relational database engine available for all applications.
4) Android Runtime Library (RunTIme libraries)
Most functions of the core library of programming languages. Android includes a core library, which provides Java
Each Android application runs in its own process and has an independent Dalvik virtual machine (Dalvik VM) instance. Dalvik is designed to efficiently run multiple virtual systems simultaneously.
The virtual machine of the program, its executable file (Dalvik Dalvik virtual machine is developed by Google to interpret and execute the Java executable compiler, and then through SDK? Format) format file (.dex) optimized for small memory usage . At the same time, the Dalvik virtual machine is based on registers, and all classes are converted into ".dex" format by the "dx" tool in Java to be executed by the virtual machine. The Dalvik virtual machine depends on some functions of the Linux kernel, such as the threading mechanism and the underlying memory management mechanism.
5) Linux kernel
Android's core system services depend on the Linux 2.6 kernel, such as security, memory management, process management, network protocol stack, and driver model. The Linux kernel also serves as an abstraction layer between the hardware and software stack.
The architecture of the Android media library system OpenCORE is shown below:
Pictured: the composition of the Android media library software
The code of OpenCore is very huge. It is based on C ++ implementation and defines a full-featured operating system porting layer. Various basic functions are encapsulated in the form of a class. The interfaces between various levels use inheritance and other methods. .
In Android 2.1 and previous versions, JIT is not supported. At the Google I / O conference on May 21, 2010, Google released the Android 2.2 version. The main new features include:
Support JIT, performance has also improved;
Support Adobe Flash 10.1 and AIR (Apollo Integrated Runtime) technology;
Supports new API applications, such as voice recognition, which can quickly turn words into text messages, search for data, and even start Google Maps, etc .;
There is also a considerable degree of support in enterprise applications, such as Microsoft Exchange, Security Policies, and GAL lookup (full address search), etc., to facilitate the application of receiving instant messages and rapid transmission of content.
2.3 Technical comparison and analysis of HbbTV and GoogleTV platforms
From the above analysis, we can see that HbbTV is an extension of the MHP mode middleware platform to the Internet (IP-based transmission network). Its detailed protocol specification based on IP network channel application management can effectively apply the broadcast channel. The integration of management makes the HbbTV platform (simply middleware platform) support DVB and IP multimedia applications. The GoogleTV technology platform integrates open Linux-based software packages and uses an open source media player to play audio and video streaming media. In the core Android system of GoogleTV, there is no digital TV protocol that supports broadcast channels (DVB-C / S / T) (at least not yet), so it cannot be used by digital TV operators to develop value-added services of. This can be said to be an important defect of the GoogleTV platform.
In general, the digital TV middleware platform (even if it is based on the MHP specification) is independent of the platform's operating system (RTOS). For example, the file system and TCP / IP protocol stack in the middleware system can be ported to In different systems, the business platform based on middleware has much lower requirements for the system's memory and storage (such as Flash, etc.); and the Android system is based on Linux, although the real-time Linux operating system has undergone many optimizations, But each application needs to run in a different process, and the storage required is still much larger than the standard middleware platform. In particular, the graphics and image processing module, media player module, and browser engine in the Android system are integrated by Google from other open source code, which is a combination and hodgepodge of a GPL software package.
Program execution method: Dalvik language is used to write application programs. DalvikVM uses a bytecode format different from JavaVM and Java, although they are optimized using Java program execution. However, the performance of the Dalvik virtual machine is improved compared to the traditional Java virtual machine, and no data has been given by an authority. Prior to the Android 2.1 version, Google claimed to have excellent performance and no need for JIT (Just-In-Time) technology. However, in the recently released Android 2.2, JIT technology is still adopted. Intellectual property issues, of course, for Java? VM is based on registers; JavaVM is based on stacks. The purpose of this move is to avoid Sun's Java.
The middleware platform based on HbbTV is developed and provided by different technology manufacturers. When the standard specifications (HbbTV, MHP or other proprietary middleware specifications) are met, the functions required by the operator can be added to suit the individuality The application needs to be interactive and interactive; GoogleTV uses an open source software package, which is free. This has become an important reason for many terminal machine manufacturers rushing.
3. The requirements of digital TV operation on middleware technology platform
Today, with the convergence of network functions and the convergence of services, digital TV operations have undergone great changes, and services and multimedia terminals that deliver video over broadband networks and based on IP protocols have emerged in large numbers. Performing on-demand, time-shifting, and recording on the IP network are common functions, and the application itself and its data are already integrated and indistinguishable. Due to the large amount of information and timeliness requirements, these applications and more and more are displayed in the form of HTML web pages, which are downloaded in time as needed, or related information is automatically updated through protocols such as Ajax and RSS.
For operators, digital TV data services may originate from signals of broadcast channels (satellite, cable or wireless, etc.) and / or broadband channels (Internet, or other IP channels). Audio, video and data may be indistinguishable from These two channels are accessed separately. In the case of limited bandwidth, the broadcast channel can be used to broadcast high-definition programs, and the use of broadband will be very wide, such as video on demand, time shift, information browsing, e-commerce, etc.
Operators' demand for digital TV is to provide value-added services and interactive applications by providing audio and video content and entertainment information. Therefore, operators need a "closed" environment that can be fully controlled to form a "Walled Garden", which will move audio and video programs, entertainment information, value-added services and applications to the platform controlled by the operator to provide users , And monitor the operation of all businesses. At the same time, operators also need to have the possibility of open systems, allowing end users to access open Internet information, and even access Internet audio and video content, such as YouTube, Youku, Tudou and other video sites. Of course, from the perspective of content security, these Internet contents need to be filtered and monitored on the server side. At the same time, operators need a stable and reliable middleware business platform to update and improve functions according to market and business development. They need professional middleware platform technology manufacturers to provide targeted and professional services for them, which is bound to The middleware platform is gradually personalized and customized according to the needs of operators. Even middleware based on the HbbTV platform, in different operator markets, will show the features that are branded by the operator, which will promote operators In the fierce competition, constantly innovating, developing users and winning competition.
The digital TV industry is undergoing profound changes, and multimedia video services are constantly emerging through multiple channels. From the perspective of ordinary people, in the past, passively watching TV was enough. Now more and more interactive content is needed, such as providing value-added services when sports events are broadcast. With more and more coming, SMS, e-mail, weather forecast can also be moved to the TV screen, in addition to this, there are some personalized community services and social TV.
4. Who will win the future technology platform?
From a business perspective, there are two types of markets for digital TV: the operator market and the retail market. Digital TV operators (including broadcast and television operators and telecommunications operators) need to operate and develop in their "closed" network ("Walled Garden"), create users, and increase revenue. In a closed network, operators can enrich their services and provide application content and service quality unmatched by the open Internet. The middleware fusion service platform based on HbbTV can not only meet the needs of operators to use broadcast and / or broadband channels for value-added services, but also support operators to manage and control applications. Therefore, the HbbTV middleware platform can better meet the needs of operators, and will definitely become an indispensable business operation platform for operators.
From a technical point of view, GoogleTV has not deviated from the framework and functions of Microsoft's WebTV and Apple's AppleTV. It is another effort of WebTV or AppleTV on Internet TV. It is the technology of Internet technology transplanted into the field of streaming media video processing. Continuation of ideas. There is no doubt that using it to browse the content of Hulu, YouTube and other video sites and online news is no problem, but for digital TV operators with a large number of cable TV, satellite TV and / or IPTV TV users, We believe that it is not convenient for value-added business operations.
GoogleTV has aroused widespread concern in the industry at present. The main reason is that Google has fully opened the source code of the Android platform, allowing the source code of the porting layer of Android on the terminal to be owned by each manufacturer (each manufacturer transplants itself). We believe that the GoogleTV platform may be suitable for digital TV manufacturers to port it to terminal devices in the retail market to support Internet streaming media playback and browsing, and to increase the functions and selling points of their terminal devices. It is impossible for the operator market to use the intact GoogleTV platform. Even if some manufacturers use the GoogleTV system for the operator market, they still need to spend a lot of energy to transform the original Android system and increase the functions required by the operator. In this way, it does not become a GoogleTV platform, but only open source code is used by technology manufacturers, just like other open source code (such as WebKit, OpenGL, etc.).
In short, Google has completely opened the source code of the GoogleTV platform. Its essential purpose is to enable GoogleTV terminals to access their Android application store. They gain profits through this application store, not really for the digital TV industry to have a generally applicable technology platform. Without consideration of interest. In any case, GoogleTV is another attempt to integrate the Internet field with the digital TV field. It provides a software system reference for terminal manufacturers of home appliance manufacturers and will have a profound impact on the future development of digital TV and Internet video streaming services.
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