Design of IPTV set-top box based on EM8620L

The circuit of the IP set-top box based on the digital media processor chip em8620l has simple peripheral circuits and strong practicability. It can realize various high-quality video and audio output, and supports video on demand through the network.

iptv is the use of broadband network infrastructure, using home TV (or computer) as a display device, integrating Internet, multimedia, communication and other technologies in one, and providing multiple types of digital TV to the family through the Internet Protocol (IP) New technologies for interactive digital media services. Set-top boxes are divided into two categories. One type is to receive digitally encoded TV signals (from satellite or cable TV networks, using mpeg compression) to obtain clearer and more stable image and sound quality. This type of set-top box is generally called a TV. Set-top box. Another type of set-top box contains an operating system and Internet browsing software, connects to the Internet through a telephone network or a cable TV network, and uses a TV as a monitor to achieve Internet access without a computer.This type of set-top box is called a network set-top box. iptv set-top box.

Features of iptv set-top box

(1) High-quality audio and video output. Using high-definition technology video decoding format and Dolby Digital technology 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 functions are implemented in the set-top box. The set-top box also needs to support the demodulation of two transport streams: one for program viewing and one for program recording.

(3) Storage and playback of multimedia files. The storage of multimedia files requires a hard disk in the set-top box. And support the corresponding standard external interface. In order to browse or play the stored multimedia files, the set-top box also needs corresponding software function support, such as picture browser, video player, mp3 player, etc.

(4) Video on demand. The video-on-demand service based on the two-way platform will fully meet the user's personalized program needs. Video on demand will maximize the development and utilization of program resources. Different programs will be reasonably distributed to users with different needs to achieve interactive functions. Set-top boxes are required to have two-way functions, which can be used in the form of Ethernet, through adsl or other methods. Spread information.

em8620l chip

The main processing chip used in this topic is em8620l produced by sigma design company, which has the following characteristics: 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 audio decoder based on dsp, support dvd audio, Dolby digital 5.1 channel, mpeg-4aac, window media audio, 16-bit linear pcm, etc .; video processing And display, can process 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 On the 32-bit bus at 33 or 66MHz, the peripheral bus interface can be programmed into a variety of modes, including universal mode, connected to the external device isa-like bus, connected to the ide bus of the hard disk and the memory bus mode of the flash rom; system memory, support 32-bit, 166mhz (ddr) sdram, can be hung up to 64mb; embedded CPU support arm-4t risc instruction set, support independent direct mapping instruction and data cache.

design

Hardware system design

The hardware block diagram of iptv set-top box is shown in Figure 1.

This subject uses the digital media processor chip em8620l, the memory is connected to 64m (ddr) sdram, the front end has a front panel controller, and receives infrared signal remote control input. The system video supports high-definition output, and can also be output in analog mode. Audio can be converted to analog audio output through da conversion, and can be connected to Ethernet or wireless LAN through the PCI bus to support video on demand.

The front panel controller uses the upd16311 chip produced by nec, which 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 with em8620l is very simple, it is 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 adopts infrared decoding ic developed by a microprocessor with low power consumption and high efficiency coms technology. It can receive infrared coding ic in nec 6121/2 format.

In terms of audio, em8620l comes with audio dsp processor, so there is no external codec decoder chip in this subject. In terms of interface, the main processing chip supports iis bus and can also be output through s / pdif fiber. In this topic, the form of iis bus is used, and the lm4921dac chip produced by the outside country semiconductor company outputs analog audio signals.

On the video side, em8620l has built-in 3-channel 12-bit video dac, so no external dac is needed, and the clear output resolution can reach up to 1920 Ã— 1080i.

In terms of network interface, because the data volume of iptv is relatively large, and the current broadband network is also more popular, it uses a more commonly used and practical Ethernet interface. In this topic, the main processing chip em8620l is paired with the mac in the network processing module through the physical layer (phy) chip through the PCI bus, and is connected to the 10 / 100t Ethernet through rj45, which can fully meet the bandwidth requirements of iptv.

Software module design

The software of this subject is based on the design of espial's evo platform. The core software module of the bottom video playback part is based on the evo platform. The module call flow is shown in Figure 2. Figure 3 is a flow chart of a user application software design for this subject.

Among them initialize various options including initialization video, audio and display options. After that, create a user api routine and allocate memory space for it. Decoding chain control is turned on and set to various decoder sources. If it fails, skip to clean up. If all settings are correct, enter an infinite loop, wait for keyboard input and perform corresponding operations, including media playback pause, search, fast forward and other basic operations, set the volume, set the system (ntsc or pal system), set the output mode, Set the stream monitoring, osd and bit rate, change the screen size, increase or decrease the pixel value to read and display the type and language of each stream.

This article introduces the key technology and characteristics of iptv set-top boxes, and designs the circuit of ip set-top boxes based on digital media processor chip em8620l. The peripheral circuits are simple and practical, and can achieve various high-quality video and audio output, and support through the network Video on demand, if time and conditions permit, you can plug in a hard disk through the peripheral bus interface to achieve program recording, multimedia file storage and playback and other functions. 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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