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DAV Nguyên tắc và các ứng dụng P3

Tham khảo tài liệu 'dav nguyên tắc và các ứng dụng p3', kỹ thuật - công nghệ, kĩ thuật viễn thông phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Digital Audio Broadcasting Principles and Applications. Edited by Wolfgang Hoeg Thomas Lauterbach Copyright 2001 John Wiley Sons Ltd ISBNs 0-471-85894-3 Hardback 0-470-84170-2 Electronic 3 Audio Services and Applications THOMAS BOLTZE WOLFGANG HOEG and GERHARD STOLL 3.1 General The DAB system is designed to provide radio services and additional data services. This chapter focuses on the main audio services as the central application. The audio services use MPEG Audio Layer II to provide mono stereo and multichannel programmes to the listener. Although the first broadcast applications and receivers will only supply stereo programmes the migration to multichannel services is nevertheless already included in the system. Data services will become more and more important and one can currently see many new ideas on their use being developed and tested. Most advanced is the Internet but it is easy to envisage that the data capacity of the DAB system can be used for very similar services. This chapter focuses on the main service of DAB - the audio broadcasting service - and the standard that is being used. We intend to give the reader an understanding of the features of the audio system and the possible pitfalls without going into too many details that the user content provider broadcaster and listener has no influence on. With the introduction of the Compact Disc and its 16-bit PCM format digital audio became popular although its bit rate of 706 kbit s per monophonic channel is rather high. In audio production resolutions of up to 24-bit PCM are in use. Lower bit-rates are mandatory if audio signals are to be transmitted over channels of limited capacity or are to be stored in storage media of limited capacity. Earlier proposals to reduce the PCM rates have followed those for speech coding. However differences between audio and speech Digital Audio Broadcasting Principles and Applications edited by W. Hoeg and T. Lauterbach 2001 John Wiley Sons Ltd. 74 Digital Audio .