嵌入式音频网络同步传输系统设计与实现

发布时间：2018-03-09 14:11

本文选题：音频传输　切入点：嵌入式　出处：《电子科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：在数字网络化时代,人们追求的是随时随地的动态获取和播放音频流,这对专业音频信号网络化传输的同步和延时提出了更高的要求。时钟同步和低延时问题一直是网络传输技术的难点,设计高时钟同步精度、实时、低成本的音频网络传输是目前专业音频领域内的研究热点。本文在研究分析现有音频网络传输技术的基础上,针对时钟同步与低延时问题设计了一套基于嵌入式的音频网络同步传输系统。实现了专业音频数据信号亚微秒级时钟同步和低延时网络传输,具体的工作和创新如下:1.研究一种基于Cortex-A9体系结构的Exynos4412处理器为核心的嵌入式音频网络同步传输系统的设计方案。根据设计方案搭建系统的硬件平台,具体包括音频信号采集与处理、网络控制传输、硬件支持PTP(Precision Time Protocol)、同步媒体时钟生成等功能模块电路设计与实现。根据设计方案搭建系统的软件平台,在硬件平台中植入嵌入式Linux操作系统,完成网络控制传输、硬件支持PTP、媒体时钟生成等模块驱动程序的编写。设计PTP程序实现高精度的时钟同步,设计RTP(Real-time Transport Protocol)程序实现专业音频信号的实时传输。2.时钟同步功能设计。音频网络传输设备易受多种外界因素影响而导致设备间产生时间误差,这种误差会随时间推移而累积,极大的影响音频数据传输的速度和质量。为解决这个问题,本文设计了一种时钟同步机制,完成时间同步与时间的校正。在同步过程中,引入了PTP精准时钟同步技术完成设备间时间信息的交互,能够实时的计算出主从设备间时间的偏差。同时,在时间的校正机制中,设计了硬件支持PTP时钟的电路模块,利用同步过程中计算出的时间偏差值对本地时间进行相应的调整,使得设备时间同步到源设备上。3.音频媒体时钟重构功能设计。传统的音频传输设备间是通过专用同轴电缆来分配音频时钟信号以实现各设备音频媒体时钟的一致,但在传输设备较多的系统中,成本也会相应的提高。针对此问题,本文设计了一种依绝对时间重构媒体时钟的方法,根据同步过程中计算出的时间偏差值来调整本地的参考时钟,从而获得时钟频率和相位与源时钟对齐的音频媒体时钟,并采用锁相环技术对已同步的音频媒体时钟进行分解,得到音频处理中需要的其他时钟。
[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.

【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN919.34

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