Broadly speaking, DVB (Digital Video BroadcasTIng) technology refers to the broadcasting of "data containers" that can transmit all types of data [1]. DVB simply transmits compressed images, sounds or data to the receiving end through these "containers". The "service information" of DVB plays the role of the container title, ensuring that the receiver knows how to decode it. The key difference between DVB and other data broadcasting systems is that different data units in the container can carry independent timing information. For example, even if the sound and image do not arrive at the receiver at the same time, the sound can be synchronized with the video information in the receiver, which is a different convenience from traditional TV programs.
The DVB method has strong adaptability. For example, a 38Mbit/s data container can support eight standard television program (SDTV) channels, four enhanced television program (EDTV) channels, or one high-definition digital television (HDTV) channel. At present, the DVB satellite communication system is mainly used to transmit multiple SDTV programs and related sounds and data. DVB is also used for data broadcasting services, such as access to the Internet.
The MPEG-2 standard was adopted by DVB for the encoding of sources such as sound and video information, and multiplexed a certain number of source data streams and auxiliary information into a single data stream suitable for transmission. Therefore, many parameters, domains and structures in DVB baseband processing are the same as those defined in MPEG-2.
DVB service, it is a digital broadcasting technology based on MPEG-2 source coding [2], this technology has three standards:
1. DVB-S, which is mostly used in satellite transponders, with a bandwidth of 26MHZ-72MHZ;
2. DVB-T, which is aimed at terrestrial broadcasting;
3. DVB-C is mainly used on cable TV. The signal of DVB-C digital video broadcasting system is usually transmitted by QAM (Quadrature Amplitude and Phase Modulation).
MPEG-2 takes into account both high-quality images and high compression ratios, from VHS image quality with a bit rate of 2MB/s to high-definition television (HDTV) with a bit rate of 18MB/s. The general MPEG-2 encoder can be selected by the user to compress the TV signal of a channel into digital signals such as 2MB/s, 3MB/s, 4MB/s, 5MB/s, 6MB/s and 8MB/s. Actual observations show that images compressed at 6MB/s and 8MB/s are basically the same as uncompressed images, but on fast sports images compressed at 4MB/s, image defects can be seen. Therefore, sports programs generally use a bit rate of 5MB/s or more, standard-definition television (SDTV) uses a bit rate of 4MB/s, and ordinary TV programs use a bit rate of 2MB/s-3MB/s.
The hardware function of DVB-C set-top box is realized by eight functional modules, including tuner, QAM demodulator, MPEG-2 demultiplexing, MPEG-2 decoding, video encoding, audio D/A, and user control interface. Figure 2 is a simplified diagram of the composition of a DVB set-top box.
Digital compression cable television receiver (set-top box DVB-C) is a new technology that realizes the digitization of television signals for transmission and reception on cable television cables. The digital transmission of TV signals has the advantages of strong anti-interference, no transmission loss, convenient and reliable encryption, and high quality of received audio and video. Set-top boxes can open up the uplink channel in the future, laying the foundation for cable TV to open high-speed Internet and other services.
Advanced applications of DVB technology include multimedia data broadcasting, Internet over-the-air transmission, interactive broadcasting services and combined with GPRS technology for mobile communications.
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