What is Remote TV Viewing?

Internet TV is also called IPTV (Interactive Personality TV). It uses televisions, personal computers, and handheld devices as display terminals, and accesses broadband networks through set-top boxes or computers to realize digital TV, time-shift TV, interactive TV, and other services. Appearance has brought a new TV viewing method to people, which has changed the passive TV viewing mode in the past, and realizes TV on-demand viewing and stop-and-see.

Network TV

IPTV is also called IPTV (Interactive Personality TV). It uses televisions, personal computers, and handheld devices as display terminals and is accessed through a set-top box or computer.

The front-end acquisition coding system encodes the analog or digital signals according to the standard and transmits them to the server. The server then transmits the data to the client's computer or set-top box. The client decodes the data and displays it to the monitor or television.

Play network content via USB interface

Copy movies, pictures or songs downloaded from the Internet to

Generally speaking, network TV can be divided into three forms according to the terminal, namely the PC platform, TV (

Video digitization, transmission IP, and streaming media.

(1) IP network (narrowband, broadband, metropolitan area network, local area network)

(2) Coaxial cable network

(3) Mobile network (second and third generation mobile, wireless LAN)

A network TV set-top box is an interface device that can provide analog audio and video interfaces, so that analog TV can receive programs normally; at the same time, it can also provide digital TV, digital broadcast interfaces, and provide interactive functions. One end is connected to the coaxial cable of the cable television network, and the other end is connected to the user's television at home. Designed for users who do not plan to buy and use computers. SA (Scientific-Atlanta) designed the first Digital Set-Top Box for Time Warner Cable's Full Service Network (FSN) in Orlando in 1994. The digital set-top box using SGI's MIPS chip and software technology will be a computer Technology brings home appliances.

In addition to providing digital TV and digital broadcast interfaces, the set-top box provides interactive functions, including telephone interfaces, computer data interfaces, and even cameras and game consoles. It can receive and store certain instructions from users, and has a central processing unit that controls the work of various parts of the converter on the machine, can perform heavy numerical calculations, and decompress and output digital video / audio signals. The set-top box is actually a multifunctional computer. The hardware structure of the digital set-top box is introduced here, so that everyone can have a general understanding and understanding of the hardware structure of the digital set-top box.

Due to the use of analog channels, in order to ensure the reliability of data transmission and low bit error rate, forward error correction coding is essential. DVB uses Reed Solomon coding. RS codes are a type of multi-ary BCH with strong error correction capabilities. The core of a digital set-top box is digital video technology. The MPEGII decoding module can be called a core module other than the CPU. In MPEG II digital transmission, interleaving coding is used. First, the code stream needs to be deinterleaved. The video, audio, and data code streams are separated , And the decoding of video codes. After the above steps, the MPEGII stream becomes a video (CCIR656 format) and audio digital signal. The MPEG multiplexer combines the various program streams and data streams together, and sends it to the radio frequency modulator in an MPEG2 data format of 188 bytes as a frame and provides an electronic program guide (EPG).

The "peripherals" of digital set-top boxes are televisions and audio systems. Digital audio and video signals must be converted to analog audio and video signals. Take MC44724 from Motorola as an example. MC44724 can convert ITU601, 656 standards 4: 2: 2 parallel video data Video, S-Video, Y / Cb / Cr, or R / G / B converted to PAL or NTSC format. The extended VBI (Vertical Blanking Interval) information input port is used to display graphic information. Audio DACs are very common and are not covered here. Modern audio systems support Dolby Pro Logic and Lucasfilm Home THX home theater systems. Digital audio signal processing chips need to be used to process digital audio signals before the audio DAC. Currently there are special processing chips and digital signal processing chips DSP for processing. the way.

The digital set-top box works in the state of the cable television network. The cable television network uses analog transmission. Therefore, digital signals must be modulated and demodulated to transmit on the analog channel. The modem is a key component of the system. It is technically similar to the principle of a telephone modem. However, a higher modulation method is used, and 64QAM or 256QAM is mostly used in the downlink. 64QAM is used as the standard modulation method in DVB-C (Digital Video Broadcast by Cable) and DAVIC. Motorola s MC92305QAM demodulation chip is used as an example. The digital signal rate of 64QAM modulation on the analog bandwidth can reach 42Mbit / S. There are usually two methods for uplink. One is to use a telephone line as an uplink channel, and the other is to use a two-way HFC network. QPSK is used as the modulation scheme. The QAM or QPSK modulator modulates the data stream in MPEG format in a standard PAL channel, and sends it out with other video modulation signals.