The circuit of the IP set-top box based on the digital media processor chip em8620l has simple peripheral circuit and strong practicability, can realize various high-quality video and audio output, and supports video on demand through the network.
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Iptv is a broadband network infrastructure, using home TV (or computer) as a display device, integrating Internet, multimedia, communication and other technologies, providing a variety of technologies including digital TV to the home through Internet Protocol (IP). New technology for interactive digital media services. Set-top boxes are divided into two categories. One is to obtain clearer and more stable image and sound quality by receiving digitally encoded TV signals (from satellite or cable networks, using mpeg compression). This set-top box is generally called TV. Set-top box. Another type of set-top box contains an operating system and Internet browsing software. It connects to the Internet through a telephone network or a cable TV network, and uses a TV as a display to realize Internet access without a computer. This set-top box is called a network set-top box. This article describes this. Iptv set-top box.
Iptv set-top box features
(1) High quality audio and video output. Using high-definition video decoding format and Dolby Digital audio decoding output, users can experience the shock of multi-channel digital stereo and clear and realistic programs at home.
(2) Program recording. The set-top box is required to have a hard disk, and the corresponding software function is implemented in the set-top box, and the set-top box side is required to support demodulation of two transport streams: one for program viewing and one for program recording.
(3) Storage and playback of multimedia files. Storing multimedia files requires that the set-top box has a hard disk. And support the corresponding standard external interface. In order to browse or play stored multimedia files, the set-top box also needs corresponding software function support, such as picture browser, video player, mp3 player and so on.
(4) Video on demand. The video on demand service based on the two-way platform will fully satisfy the user's personalized program requirements. Video on demand will maximize the development and utilization of program resources. Different programs will be allocated to users with different needs, and interactive functions will be implemented. The set-top box is required to have two-way functions. It can be Ethernet-based and returned via adsl or other means. Pass the message.
Em8620l chip
The main processing chip used in this project is em8620l produced by sigma design company. It has the following features: mpeg decoding, which can decode two mpeg video streams at the same time; wmv9 decoding; supports multiple dvd/media formats, including audio, jpeg, mp3 and Mpeg-4 avi file; audio decoding and i/o, embedded dsp-based audio decoder, support for dvd audio, Dolby Digital 5.1 channel, mpeg-4aac, window media audio, 16-bit linear pcm, etc.; video processing And display, can handle up to five independent video or image planes, support 2D image acceleration, support digital output, analog output and component analog output; bit stream demultiplexing; pci and peripheral bus, pci bus is working In the 32-bit bus of 33 or 66mhz, the peripheral bus interface can be programmed into multiple modes, including general mode, connected to the external device isa-like bus, connected to the hard disk ide bus and flash rom memory bus mode; system memory, support 32-bit, 166mhz (ddr) sdram, up to 64mb; embedded cpu supporting arm-4t risc instruction set, support independent direct mapping instructions and data cache.
design
Hardware system design
The hardware block diagram of the iptv set-top box is shown in Figure 1.
This topic uses the digital media processor chip em8620l, the memory is connected to 64m (ddr) sdram, the front end has a front panel controller, receiving infrared signal remote input. The system video supports HD output or analog output. The audio aspect can be converted to analog audio output through da conversion, and can support video on demand through Ethernet or wireless LAN via pci bus.
The front panel controller uses the upd16311 chip produced by nec. The chip is a chip that supports fip or vfd display. The chip supports two display modes: 12-segment 16-bit or 20-segment 8-bit. The connection to em8620l is very simple, in serial mode (clk, stb, din, dout).
The infrared input part adopts the receiving chip irdc367 of nec company's rc5 protocol format, which works in asynchronous serial mode. The chip uses an infrared decoder ic developed by a microprocessor with low power and high efficiency coms technology, which can receive infrared coded ic in nec 6121/2 format.
The audio aspect em8620l comes with an audio dsp processor, so there is no external external codec decoder chip in this topic. The interface main processing chip supports the iis bus and can also be output through s/pdif fiber. In this topic, the is bus is used, and the lm4921dac chip produced by the National Semiconductor Company outputs analog audio signals.
The video aspect em8620l has built in 3 12-bit video dac, so there is no need to connect external dac, and the clear output resolution is up to 1920×1080i.
In terms of network interface, because the data volume of iptv is still relatively large, and the current broadband network is also popular, a relatively common and practical Ethernet interface is adopted. In this topic, the main processing chip em8620l through the pci bus, through the physical layer (phy) chip and the mac in the network processing module, through rj45 and 10/100t Ethernet connection, can fully meet the iptv bandwidth requirements.
Software module design
The software part of this project is based on the design of espial's evo platform. The core software module of the underlying video playback part is based on the evo platform. The module call flow is shown in Figure 2. FIG. 3 is a flow chart of designing a user application software for the subject.
Initializing various options includes initializing video, audio, and display options. This is followed by creating a user api routine and allocating memory space for it. The decoding chain control is turned on and set to various decoder sources. If it fails, it jumps to the end of clean up. If all the settings are correct, enter an infinite loop, wait for the keyboard input and perform the corresponding operations, including basic operations such as media pause, search, fast forward, set the volume, set the format (ntsc or pal), set the output mode, Set flow monitoring, osd and bit rate, change screen size, increase or decrease pixel value reading and display the type and language of each stream.
This paper introduces the key technologies and features of iptv set-top box, and designs the circuit of ip set-top box based on digital media processor chip em8620l. The peripheral circuit is simple and practical, and can realize various high-quality video and audio output, and support through network. Video on demand, if time and conditions permit, you can use the peripheral bus interface to connect the hard disk to achieve program recording, multimedia file storage and playback, etc. With the popularity and development of broadband networks and digital TV, the iptv market will become more and more open, iptv The set-top box will be further expanded and improved in function, and will be more widely used.
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