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  本文選題：音頻傳輸　切入點：嵌入式　出處：《電子科技大學》2015年碩士論文　論文類型：學位論文

【摘要】：在數字網絡化時代,人們追求的是隨時隨地的動態(tài)獲取和播放音頻流,這對專業(yè)音頻信號網絡化傳輸的同步和延時提出了更高的要求。時鐘同步和低延時問題一直是網絡傳輸技術的難點,設計高時鐘同步精度、實時、低成本的音頻網絡傳輸是目前專業(yè)音頻領域內的研究熱點。本文在研究分析現有音頻網絡傳輸技術的基礎上,針對時鐘同步與低延時問題設計了一套基于嵌入式的音頻網絡同步傳輸系統(tǒng)。實現了專業(yè)音頻數據信號亞微秒級時鐘同步和低延時網絡傳輸,具體的工作和創(chuàng)新如下:1.研究一種基于Cortex-A9體系結構的Exynos4412處理器為核心的嵌入式音頻網絡同步傳輸系統(tǒng)的設計方案。根據設計方案搭建系統(tǒng)的硬件平臺,具體包括音頻信號采集與處理、網絡控制傳輸、硬件支持PTP(Precision Time Protocol)、同步媒體時鐘生成等功能模塊電路設計與實現。根據設計方案搭建系統(tǒng)的軟件平臺,在硬件平臺中植入嵌入式Linux操作系統(tǒng),完成網絡控制傳輸、硬件支持PTP、媒體時鐘生成等模塊驅動程序的編寫。設計PTP程序實現高精度的時鐘同步,設計RTP(Real-time Transport Protocol)程序實現專業(yè)音頻信號的實時傳輸。2.時鐘同步功能設計。音頻網絡傳輸設備易受多種外界因素影響而導致設備間產生時間誤差,這種誤差會隨時間推移而累積,極大的影響音頻數據傳輸的速度和質量。為解決這個問題,本文設計了一種時鐘同步機制,完成時間同步與時間的校正。在同步過程中,引入了PTP精準時鐘同步技術完成設備間時間信息的交互,能夠實時的計算出主從設備間時間的偏差。同時,在時間的校正機制中,設計了硬件支持PTP時鐘的電路模塊,利用同步過程中計算出的時間偏差值對本地時間進行相應的調整,使得設備時間同步到源設備上。3.音頻媒體時鐘重構功能設計。傳統(tǒng)的音頻傳輸設備間是通過專用同軸電纜來分配音頻時鐘信號以實現各設備音頻媒體時鐘的一致,但在傳輸設備較多的系統(tǒng)中,成本也會相應的提高。針對此問題,本文設計了一種依絕對時間重構媒體時鐘的方法,根據同步過程中計算出的時間偏差值來調整本地的參考時鐘,從而獲得時鐘頻率和相位與源時鐘對齊的音頻媒體時鐘,并采用鎖相環(huán)技術對已同步的音頻媒體時鐘進行分解,得到音頻處理中需要的其他時鐘。
[Abstract]:In the digital network era, people's pursuit of the acquisition and playback of audio stream whenever and wherever possible the dynamic, which puts forward higher requirements for professional audio signal network transmission synchronization and clock synchronization. Time delay and low delay is a difficult problem of network transmission technology, the design of high precision clock synchronization, real-time, low audio network transmission cost is the hot topic in the field of professional audio. This paper analysis the existing network audio transmission technology in research, for clock synchronization with low delay problem to design a set of embedded audio network based on synchronous transmission system. The professional audio data signal sub microsecond clock synchronization and low network delay, specific the work and innovation are as follows: 1. the design of synchronous transmission system of a Exynos4412 processor based on Cortex-A9 architecture as the core of the embedded audio network According to the design scheme. To build the hardware platform of the system, including audio signal acquisition and processing, network transmission control, hardware support PTP (Precision Time Protocol), and the synchronization of media clock generation module circuit design. According to the design scheme of building the system software platform, embedded Linux operating system on the hardware platform. Complete control of network transmission, hardware support PTP, program driven media clock generation module. The design of PTP program to achieve high precision clock synchronization design, RTP (Real-time Transport Protocol) program to realize the real-time transmission of.2. clock synchronization function design of audio signal. The audio transmission equipment is easily affected by various external factors caused by time the error between devices, this error will be accumulated with time, speed and quality of audio data transmission greatly. For the solution Solve this problem, this paper designs a kind of clock synchronization, time synchronization and time correction is completed. In the process of synchronization, interactive introduction of PTP precision clock synchronization technology to complete the time information between devices, capable of real-time calculation of time deviation between master and slave devices. At the same time, the time correction mechanism, circuit module the design of hardware support PTP clock, the time deviation calculated during synchronization value adjusted to local time, making the equipment design time.3. audio media source device synchronous clock reconstruction function. The traditional audio transmission equipment is through special coaxial cable to distribute the clock signal to achieve the audio equipment and audio media the clock is consistent, but in the system transmission equipment more, the cost will be increased accordingly. To solve this problem, this paper designs a kind of absolute time in reconstruction of media The method to adjust the local clock and the reference clock according to the time deviation of calculated values in the synchronization process, so as to obtain the clock frequency and phase with the source clock clock and audio media, using the technology of PLL decomposition of synchronized audio media clock, get other clock needs in audio processing.

【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TN919.34

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相關期刊論文 前1條

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本文編號：1588872