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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(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：在數(shù)字網(wǎng)絡(luò)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(wǎng)絡(luò)化傳輸?shù)耐胶脱訒r提出了更高的要求。時鐘同步和低延時問題一直是網(wǎng)絡(luò)傳輸技術(shù)的難點,設(shè)計高時鐘同步精度、實時、低成本的音頻網(wǎng)絡(luò)傳輸是目前專業(yè)音頻領(lǐng)域內(nèi)的研究熱點。本文在研究分析現(xiàn)有音頻網(wǎng)絡(luò)傳輸技術(shù)的基礎(chǔ)上,針對時鐘同步與低延時問題設(shè)計了一套基于嵌入式的音頻網(wǎng)絡(luò)同步傳輸系統(tǒng)。實現(xiàn)了專業(yè)音頻數(shù)據(jù)信號亞微秒級時鐘同步和低延時網(wǎng)絡(luò)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(jié)構(gòu)的Exynos4412處理器為核心的嵌入式音頻網(wǎng)絡(luò)同步傳輸系統(tǒng)的設(shè)計方案。根據(jù)設(shè)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(wǎng)絡(luò)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(shè)計與實現(xiàn)。根據(jù)設(shè)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(wǎng)絡(luò)控制傳輸、硬件支持PTP、媒體時鐘生成等模塊驅(qū)動程序的編寫。設(shè)計PTP程序?qū)崿F(xiàn)高精度的時鐘同步,設(shè)計RTP(Real-time Transport Protocol)程序?qū)崿F(xiàn)專業(yè)音頻信號的實時傳輸。2.時鐘同步功能設(shè)計。音頻網(wǎng)絡(luò)傳輸設(shè)備易受多種外界因素影響而導(dǎo)致設(shè)備間產(chǎn)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(shù)據(jù)傳輸?shù)乃俣群唾|(zhì)量。為解決這個問題,本文設(shè)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(zhǔn)時鐘同步技術(shù)完成設(shè)備間時間信息的交互,能夠?qū)崟r的計算出主從設(shè)備間時間的偏差。同時,在時間的校正機制中,設(shè)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(yīng)的調(diào)整,使得設(shè)備時間同步到源設(shè)備上。3.音頻媒體時鐘重構(gòu)功能設(shè)計。傳統(tǒng)的音頻傳輸設(shè)備間是通過專用同軸電纜來分配音頻時鐘信號以實現(xiàn)各設(shè)備音頻媒體時鐘的一致,但在傳輸設(shè)備較多的系統(tǒng)中,成本也會相應(yīng)的提高。針對此問題,本文設(shè)計了一種依絕對時間重構(gòu)媒體時鐘的方法,根據(jù)同步過程中計算出的時間偏差值來調(diào)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(shù)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(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN919.34

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相關(guān)期刊論文 前1條

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本文編號：1588872