With the general trend of "3C" integration of home appliances, communications and consumer electronics, IPTV systems based on IP broadband networks have gradually become hot spots. IPTV (Internet Protocol TV or InteracTIve Personal TV) is also called interactive network TV. It is an infrastructure that utilizes broadband networks. It generally uses IP set-top boxes as the main terminal equipment, and integrates various technologies such as Internet, multimedia, and communication. A new technology for home users with a variety of interactive digital media services, including digital TV. This paper proposes and designs a broadband information terminal based on Blackfin BF561. The terminal adopts the most active embedded system technology in the computer field, and designs and implements the broadband information terminal with the high-performance DSP processor and the embedded Linux operating system as the core. The broadband information terminal is actually a low-end IPTV set-top box, which can provide users with Internet information browsing and streaming video playback services. The terminal can present an ideal media playback effect under the existing network conditions (mainly network bandwidth) of domestic telecom operators. The terminal has been successfully commercialized and obtained bulk purchase in the rural informationization project of Sichuan Telecom. At present, relying on the rural comprehensive information content platform deployed by Sichuan Telecom, thousands of broadband information terminals have been extended to rural areas in Sichuan. 2 system design 2.1 Overall system design The system design principle of the broadband information terminal based on DSP is shown in Figure 1. The uClinux operating system, audio and video decoding, various network protocols, embedded browser, streaming media player, and graphical user interface are all processed by BF561, through PPI, SPORT, UART and other communication interfaces are connected to external peripheral devices. The Blackfin BF561 is a dual-core DSP processor introduced by Analog Devices in recent years for high-end multimedia applications. The BF561 is a symmetric multiprocessor (SMP) device. Each of its cores has its own high-speed L1 instruction and data memory, while the two cores share 128KB of L2 memory. Each core has access to a variety of peripherals, including video interfaces, serial ports, and timers. [2] In addition, the Blackfin processor features a high-performance processor core, high-bandwidth DMA performance, an instruction set defined for enhanced video processing, efficient control processing, tiered memory, and dynamic power management. In the design, one core of the BF561 handles all "MCU-type" tasks, such as graphics overlay, network management and process control, while running the uClinux operating system; the other core performs the main DSP functions. We also put MP3 audio decoding in the kernel that handles the "MCU type" task, while the other core only performs MPEG4 video decoding. [4] The following describes the system host from the video process, audio flow, and network communication. 2.1.1 Reproduction of video signals The video signal (video, text) transmitted from the network to the local area is processed by the signal processing of the Ethernet controller, input to the BF561 through the bus, processed into the ITU656 format by the MPEG4 decoder, and converted into a CVBS or Y/C signal by the DAC. Displayed on the TV, thus realizing the reproduction of the video image. The DAC uses the Analog Devices ADV7179KCP chip. 2.1.2 Pickup and reproduction of audio signals The audio signal (MP3) transmitted from the network to the local is processed by the signal processing of the Ethernet controller, input to the BF561 through the bus, processed into the ITU656 format by the MP3 decoder, and converted into an analog audio signal by the DAC, and implemented on the television. put. The DAC uses the WM8731S chip from WOLFSON. [5] 2.1.3 Network Processing This system uses a single network port design. The Ethernet controller uses SMSC's LAN9115 full-duplex 16BIT Ethernet controller to accommodate 100Base-TX/10Base-T. 2.2 System software design The system software design principle is shown in Figure 2. The system application runs on the uClinux operating system. The kernel version is 2.6.11. The terminal application uses multi-process parallel and inter-process communication mechanism. â— Kernel driver (1) network driver; (2) PPI video output module; (3) based on SPORT0 audio driver; (4) A module that interacts with another core. â— Function modules running in kernel mode (1) a video decoding module based on a TImer driver; (2) Complete the audio AdaptIve Jitter Buffer function and audio decoding. â— User program (1) GUI user program interface module; (2) embedded browser module; (3) RTSP streaming media player module; [6] (4) Decoder interface, RTP/RTCP module. 3 system practice The terminal has been implemented and has been successfully introduced to the market after several rounds of system testing and quality improvement, and has excellent cost advantages and good scalability at this stage. As shown in Figure 3, it is a screenshot of the main menu of the terminal graphical user interface. In the implementation process, since it is custom designed for customers, video decoding and audio decoding are respectively determined to be MPEG4 and MP3. In fact, based on the DSP characteristics of BF561, it is also possible to design various other decoders such as H264 and AVS in the system, thereby realizing broadband information terminals supporting multiple decoder formats, and has good scalability. In fact, many of Analog Devices' partners have successfully implemented the MPEG4/H264 CIF/D1 decoder on the BF561. 4 Conclusion The cost advantage of this system is obvious. The Blackfin uClinux operating system is provided free of charge by the technical website supported by Analog Devices. ADI also brings along the website to provide continuous technical support (such as version upgrades, new project resources, etc.). In fact, because the ADI BF561 naturally has the characteristics of a symmetric multiprocessor (SMP) architecture, it uses a full two processors connected through a high-speed channel and shares peripherals and memory space [2], enabling developers to The computational applications are evenly distributed across each core, maximizing the use of dual-core processor resources and effectively controlling costs. On the other hand, due to the programmable nature of the DSP, the system not only makes full use of the processor resources, but also has significant advantages in the subsequent expansion of various decoding capabilities (such as AVS). In short, this paper combines the current "3C" convergence trend and the development status of IPTV technology, proposes and designs a DSP-based broadband information terminal. The terminal has high reliability, good scalability and excellent performance-price ratio, and has been effectively verified in the market mass promotion.
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Figure 1 DSP-based broadband information terminal system design schematic 
The system software consists of drivers, kernel tasks, and user programs running on the uClinux kernel. 
Figure 3 screenshot of the graphical user interface main menu