【正文】 and an integrated circuit ( IC ) manufacturers in close cooperation ( ( / L more than a dozen and Dolby techniques related to integrated circuit manufacturers have license the production of all kinds of product development ). By Dolby training consultant for world production center to provide advisory services, to help solve the film, video and music broadcast media sound track technical problems. When the technology into the multichannel digital audio field laboratory, Dolby not only in the t。 for each license 畢業(yè)設(shè)計(jì)（論文）外文資料 9 production of the product prototype ( prototype ) test。 the disadvantage of reducing coding efficiency, because of the need to transfer the bit allocation information while occupying a part effective bits. To the adaptive method did not get encoder clear bit allocation information, but from a digital stream in which the bit allocation information, has the advantages of no occupation of the effective bits, thus has higher transmission efficiency. Its drawback is from received data to calculate the bit allocation, if the calculation is too plex to the rising cost of decoder. In addition, the decoder algorithm also with encoder auditory model change. AC3using hybrid backward / forward adaptive bit allocation, in enhancing the rate and reduce the cost of strikes a balance between. AC3 decoder decoding principle basically is encoded by the reverse process, firstly, the decoder must with the encoded data stream synchronization, and then from a data error correction of digital flow separation control data, system configuration, the encoded spectral envelope and the quantized mantissas and other content, according to the sound spectrum envelope to generate the bit allocation information, the mantissa part of inverse quantization, restoring the transform coefficient exponent and mantissa, after synthesis filter banks, the data from the frequency domain to time domain, the final output of the PCM sample signal reconstruction. Through the understanding of AC3, you can see the AC3technology makes full use of the human ear sensory model, according to the different properties of signal, to take the corresponding effective algorithm, achieved at a high quality under the premise of achieving a higher rate for the intended purpose, is a very efficient and economical digital audio pression system. AC3 is the American digital television system of mandatory standard, is the European digital television system remended standard, at the same time, AC3or DVD system of pulsory standards. At present our country is the development and promotion of digital TV system, all have reasons to believe that AC3 technology will have a good prospect of application. Dolby Chun chamber ( About DolbyLaboratoies ) from the analog noise reduction ( analog noisereduction ) to the digital code ( digitalcode ), Dolby has concentrated on rooted in laboratory to ear sound perception based audio processing development. In the process of development, Dolby has always been the emphasis is on the critical listening and tested. Either analog or digital program program, their results are the same, with low cost, greatly improves the efficiency of munication media. In some cases, it also for the improvement of new products, such as: Dolby surround sound ( DolbySurround ) and home theater ( home theater T ) make contribution. The Dolby laboratory consists of the following ponents: investment and Technology Development Engineering Department, occupation audio product design and manufacturing sector, experts the anization and distribution of all over the world in the field of support group. Dolby products from panies located in modern American and British manufacturing plant. Lyrics by the world39。 in quantization process, the mantissa is shaking, shaking the pseudo random number generator can be on a different platform to get the same results. By the end of six blocks of the spectral envelope, coarse quantization of the mantissa and the corresponding parameters consisting of AC3 data frame format, continuous frame merged into a digital stream output. By the time domain is transformed to the frequency domain block length selection is the exponential transform coding based on. As defined in AC3two length switching, a512sample value point of the long block, a256sample value point of short block. In the analysis of signal spectrum, to deal with the channel signal blocks cut made longer, so that you can get a better frequency resolution, but also can get higher coding efficiency. But long data block may contain a number of different possible recognition of noise, such as preecho. That is to say the ear due to time and frequency exists on the shadowing effect in the exponential transform coding is a contradiction, not at the same time, must plan as a whole processing. For the steady state signal, whose frequency varies with time transform slow, in order to improve the coding efficiency, requirement filter has good frequency resolution, which requires a long block。s top decoder. Other semiconductor manufacturers have been or are ready to supply the AC3 decoder integrated circuit. Dolby and digital AC3 is Dolby39。t because video interference blind audio, sound burr or other distortion. Dolby E audio and video frames in the sequence are pletely corresponding, can achieve precise audio and video integrated editing. More importantly, by use of this new type of coding technology, the existing radio and television system without largescale transformation can spread multichannel digital TV audio signals, thereby greatly reducing the system cost. Dolby E application is in digital television stations intermediate transfer, from a local television program transmitted by satellite to another local TV station. Dolby E in conveying to the transmitting terminal will be converted