subject: [photo] T-dmb Standard Based Mobile Tv Solutions - Mobile Tv, T-dmb, H.264-hc Network Broadcasting [print this page] System developed in South Korea's national standard of digital multimedia broadcasting T-DMB system design and achievement. Article briefly describes the beginning T-DMB the reason the birth, then a more detailed description of its mobile television service used by a number of treatment technologies, including H.264, MPEG-4, MPEG-2TS, etc. Finally, the DMB developments in China and to look into the platform as a mobile TV broadcast market prospects.
Key words T-DMB mobile TV, audio and video encoding
1. INTRODUCTION With the constant improvement of living standard, people have a wide range of trends in information consumption has become increasingly clear. Traditional fixed terrestrial television has been difficult to meet people's consumption demand, people not only want to watch anytime, anywhere high-definition video screen broadcasting, also hope to receive some of such real-time data, images, sounds, stock, finance, and Information. In Korea, the United States because they use their domestic digital TV standard ATSC digital terrestrial television broadcasting operations, and this standard can not support mobile TV services. In people the growing demand for mobile TV, under the circumstances, Koreans after more than two years available on the currently available technology standards for terrestrial broadcasting some careful comparative analysis, the final selection of the DABEureka-147 European standard as the Republic of Korea terrestrial mobile TV services to carry out transmission standard, and thus established the ground in Korea mobile TV national standard T-DMB.
T-DMB standard as the inheritance and development of DAB, DAB in addition to the standard originally used by the relevant technology, to video broadcasting, also used a series of new technologies. Included in the video compression used for low bit rate video services, video coding standard MPEG-4AVC/H.264, program audio compression is used BSAC, data exchange using the BIFS. DAB and MPEG-4 technology, the successful combination of people to effectively solve the needs of digital mobile TV services. DABEureka-147 as the first order on the ground sound broadcasting to digital development of standards, complete in 1994, development has become a very mature technical standards, has been in Europe and other countries and regions, including China, Korea, Canada , Taiwan, Australia to adopt as the implementation of national terrestrial digital sound broadcasting program selected. At present, European countries, especially Britain, DAB receiver chip and can be seen everywhere in the market, types are also very complete, the price is reasonable. As the development of a standard design from the beginning, DAB standard is as to the fixed and mobile devices can broadcast sound support business development, so very suitable for mobile TV services. DAB system can provide up to 1.824Mb / s bit rate for sound broadcasting with data services. Today, DAB system has been able to provide, including dynamic text, slides, radio and Web sites and other related or unrelated with the voice of business. Especially in the reuse area, DAB allow its independent data stream mode sub-channel in use, the characteristics of a Korean T-DMB development of a breakthrough.
2. DAB to DMB development The transition from the current DAB system to DMB, DAB radio without the need of the existing front-end for any changes, as long as the front-end devices to introduce a DMB video encoder. Can achieve the transition from DAB to DMB. Figure 1 shows the structure of Korean T-DMB-level map. As can be seen from the chart, DMB system still continue to use the DAB of the whole system, only DAB's MSC (main service channel) in the carved out a separate subchannels for video services. The DAB inherent in the original as the voice of business data services remain the same, which makes the deployment of DMB relatively easy. The new video service, mainly through the front of the DMB video encoder to achieve, video encoder encodes a stream of data to ETI (composite group Transport Interface) signal form to flow through the DAB multiplexer means multiplexing mode subchannel, to work with from the other road into audio or data multiplexing up to 2.048Mb / s of ETI transmit data stream, and then assigned to the DAB ETI data stream synchronization network launch various transmitters.
Figure 1 T-DMB Chart 1. Audio and video encoding processing
Korea T-DMB standard using a limited bandwidth will continue to provide high compression performance of the compression standard MPEG-4AVC video compression standard. The audio in the video compression standard choice, the use of relatively low royalty audio compression standard MPEG-4BSAC not AAC +. The video is accompanied by some of the data services or need to provide some interactive applications, it was an encoded using MPEG-4BIFS. In order to facilitate the development of commercial receivers, T-DMB uses MPEG-4 compression standard required in the decoding processing is relatively easy to structure. Figure 2 shows the DMB video business processes.
Figure 2 DMB video service processing flow chart
Can be seen from the diagram: the DMB video encoder, the use of the MPEG-4system part of the standard H.264-encoded video respectively, BSAC audio coding and interactive data encoded BIFS content synchronization. First to use MPEG-4SL (sync layer) packet format for video, audio and interactive data package, and then to synchronize MPEG-2TS packet multiplexed transport stream. And then to forward error correction, the final approach to complex flow model used in DAB system. Techniques used include RS FEC coding, convolutional interleaving technology. Use of FEC is primarily due to improved data flow error resilience performance. To get good sound quality for DAB required bit error rate (BER) is not greater than. However, DMB, we should realize the receiving end of the video business, stable and reliable receiver, bit error rate (BER) requirements up to. To meet this demand, South Korea T-DMB standard used in the DVB-T standard also uses forward error correction (FEC). The use of RS (204,188) of the MPEG-2TS encoded stream and then packaged for convolutional interleaving. 188 bytes per TS packet through the RS coded into 204 byte packets, of which 16 bytes are error correction coding. After encoding, the RS encoded every 11 packets for a convolution cycle, so that you can put in the time domain burst spread in all parts of the error, reducing the probability of consecutive errors occur. Through the use of forward error correction technology, can effectively guarantee the BER below the video stream.
