基亏DSP的多路音／视频采集处理系统设计

采用TI公司的TMS320DM642型数字媒体数字信号处理器（DSP）设计多路音／视频采集处理系统，实现实时处理4路模拟视频和音频输入、1路模拟／数字视频和1路模拟音频信号输出的功能，该系统可适应PAL／NTSC标准复合视频CVBS或分量视频Y／C格式的模拟信号和标准麦克风或立体声音频模拟输入，具有PAL／NTSC标准S端子或数字RGB模拟／数字信号输出和标准立体声音频模拟输出。并给出软／硬件设计原理和电路。     

基于DSP平台的数字视频源的系统设计

提出了一种基于TI DSK6711平台的将模拟视频进行数字化处理的系统设计方案,其中视频解码模块完成复合视频信号数字化,音频A／D模块完成语音信号数字化,同时采用大容量的SDRAM存储器作为帧缓存,用FPGA完成其控制接口,整个系统以DSK6711为核心构成数据处理单元,此系统可以完成电视图像信号的去隔行扫描转换、低分辨率向高分辨率转换等视频信号处理,也可以进行实时视频和音频数据压缩处理。     

DVD-Video: multimedia for the masses

DVD (digital video disc, or digital versatile disc) is the next generation of optical disc storage technology. It's essentially a bigger, faster compact disc (CD) that can hold video as well as audio and computer data. DVD aims to encompass home entertainment, computers and business information with a single digital format, eventually replacing audio CD, videotape, laser disc, CD-ROM, and perhaps even video game cartridges. DVD has widespread-and unprecedented-support from all major electronics companies, all major computer hardware companies and most major movie and music studios, which says much for its chances of success. DVD-ROM holds computer data read by a DVD-ROM drive hooked up to a computer. DVD-Video is an application built on top of DVD-ROM. DVD-Video holds video programs played in a DVD player hooked up to a TV. The difference between DVD-ROM and DVD-Video resembles that between CD-ROM and audio CDs, including the important point that DVD-Video discs can be played in computers     

Tutorial review of magnetic recording

Most of the technologically important aspects of magnetic recording are reviewed in a nonmathematical manner. After a discussion of recording media and heads, the fundamentals of the media magnetization and writing processes are considered. The factors limiting the bandwidth, distortion, and signal-to-noise ratio of audio, instrumentation, video, and digital recording machines are analyzed. The paper concludes with some predictions on the future of magnetic recording.     

Achievements in rotary head magnetic recording

The principal achievements since 1980 in rotary head recording on magnetic tape are outlined. These developments are related to fundamental improvements in recording media, heads, the design of tape transports, and signal processing. The D-1 and D-2 video tape recorders (VTRs), the Hi-Band 8-mm video cassette recorder (VCR), and the rotary digital audio tape (R-DAT) recorders are discussed. The future of rotary head recorders for consumer digital VCRs, professional high-definition TV (HDTV) VTRs, and consumer HDTV VCRs is assessed     

1/2-inch cassette VTR for baseband HDTV signal recording

Technical details are reported for a 1/2-inch cassette videotape recorder (VTR) developed for recording the baseband high-definition TV (HDTV) signal. A recording time of 63 min was achieved by using metal-particle tape and laminated amorphous video heads. The frequency bandwidths used for luminance and chrominance signals were 20 and 7 MHz, respectively. A novel two-channel, three-segment recording method was developed for the purpose. Four-channel digital audio recording with a sampling frequency of 48 kHz and 16-b linear quantization was used. The digital audio signal was recorded on the overlapped area succeeding to the video track by using the same heads used for video recording     

一种LED显示屏音视频切换矩阵设计

针对众多视频、音频源进行数字化集中处理，通过音、视频多路转换器矩阵对多路输入信号进行自动监测，并以RS-232串口、面板键盘或专用遥控器进行控制，选择任意输入信号输出2路独立音、视频信号及1路录像监视信号，从而实现为LED显示屏提供高质量的不同的音、视频信号源并实现多路音视频源的切换输出。     

IPTV助推数字家庭时代的到来

不同行业都在关注数字家庭的发展，但数字家庭发展缓慢的现状不容忽视。现阶段来看通信和媒体娱乐业务是数字家庭市场需求的重点，基于电信网络的数字家庭通过借助IPTV的音视频和增值应用业务可以顺应此要求。IPTV业务包括基本的音视频广播、点播、时移业务，以及信息服务、音视频通信、互动游戏、即时通讯、卡拉OK、远程教育等增值应用服务，非常适合数字家庭的发展需要，将使数字家庭的应用变得更为现实。未来，进一步推动数字家庭发展需要在易用性和业务创新两个方面取得突破，需要通过设备间的协同工作，为用户提供基于数据、语音、视频的三重业务新体验。     

双音频在高清安防监控系统中的应用

介绍了HDMI数字音频和传统模拟音频两种音频格式在高清安防系统中的应用。当系统输出的视频格式为HDMI高清视频时,音频通道自动将音频数据发送给HDMI发送芯片,HDMI发送芯片将音频数据复合到视频流,并最终将音视频复合流输出到HDMI接收设备。而当系统当前输出的视频格式为VGA视频输出时,音频通道自动将音频数据发送给音频D/A芯片作数模转换,转换后得到的模拟音频信号最后输出到模拟音频接收设备。利用此方法,可以在实现HDMI数字音频输出的同时很好地兼容原有的模拟音频输出,并实现双音频流的自动选择与自由切换。     

机载多路数字视频记录仪的设计与实现

视频的压缩记录是现代航空技术中很重要的一个研究内容，通过它可以实时记录飞机的多种直观信息，对飞行指挥和作战训练起到积极的指导作用，本文介绍了一种现代数学图像处理技术实现机载多路数字视频记录的方法，与传统的模拟记录方法相比，该方法具有记录容量大，记录时间长，图像质量高等特点。     

高清晰度多媒体接口(HDMI)在雷达中的运用研究

由于HDMI是数字方式传输,它可以从根本上解决现行的机载雷达采用电视体制的PAL制或VGA制式的模拟信号在用于液晶显示时的要经历先D/A后A/D的变换所带来的损失,因此,提出用该种显示方式用于机载雷达的显示,此方法可大幅度地提高分辨率且无传输和变换损耗,本设计使用SiI9134为接口器件,数字视频形成电路由FPGA构成,实验证明此设计稳定可靠,完全可以达到产品要求。     

数码单反相机拍摄视频的音频解决方案

使用数码单反相机拍摄视频逐渐成为一种流行趋势,但通常拍摄出的视频录音质量较差,这是由单反相机本身在音频方面的设计缺陷造成的。旨在推荐几种能够提高单反相机录音质量的方法,希望为相关领域从业人员提供参考。     

一种自动等响度数字混音算法

在电视会议系统中,为获得接近真实的会议交流氛围,混音技术不可或缺。本文利用语音信号的响度特性,提出一种自动等响度数字混音算法。该算法首先利用信号平均功率和短时自相关函数进行语音活动检测(VAD),判断参与混音的每路信号中是否含有语音信号。然后,利用时变滤波器进行滤波处理,抑制混音过程中引入的噪声。最后,利用语音信号响度计算各路信号的权重,使各路语音的平均响度保持一致。仿真实验结果表明,本文的混音算法可使各路信号的平均响度基本相同,并具有良好的语音质量。      

基于网络的数字模拟混合电视接收系统的硬件设计与实现

介绍通过网络来播放数字电视和模拟电视的用户接收终端的解决方案。该方案基于Micronas的信道解调器和MPEG压缩编码芯片,可以支持NTSC、PAL、ATSC、QAM、DVB-T等模拟和数字多制式电视标准,以及Composite、S-Video、YPbPr等模拟视频信号,LR左右声道音频信号输入,通过以太网口或者PCI无线网卡与网络相连,将流媒体传输到网络上并由用户终端PC机解码播放。     

高清数字视频广播中的音频解嵌系统设计

数字视频广播的视频流中可嵌入音频数据。本文研究了符合SMPTE299M标准的高清视频流中音频嵌入原理,在FPGA上设计并实现了高清视频流音频解嵌系统,它能解出采样率为48K的16路声音通道的数字音频信号,并根据需要选择相应通道进行播放。该系统可用于数字演播室中对各个通道的声音监测及播放。     

一种室内全数字无线音频广播系统设计

介绍一种采用数字音源、数字无线传输和数字音频功率放大器的高保真无线音频广播系统,可作为室内背景音乐系统。主机使用触摸屏操作,节目源可以是音频文件、FM广播、立体声线路输入,S/PDIF光纤、数字同轴电缆,或是作为USB声卡连接计算机。从机采用高效率数字D类音频功放。主、从机之间用CC8520芯片无损传输数字音频信号。系统易于安装、工作稳定、性价比高。     

Complementary punctured-pair convolutional codes for digital audio broadcasting

Hybrid in-band on-channel (IBOC) broadcasting systems for digital audio radio have the capability of simultaneously transmitting analog FM and digital audio of CD-like quality. Due to fading and interference in the already-crowded FM band, the signal design for the hybrid IBOC system is very challenging. It has been proposed to use a method of double sideband transmission where the digital information is transmitted by means of orthogonal frequency-division multiplexing (OFDM) on both sides of the analog host FM and where the digital information can be recovered when one sideband is partially or even totally lost. This leads to an interesting channel coding problem, where we search for optimal pairs of high-rate codes that form good combined low-rate codes, which are better than classic code combining techniques. Furthermore, we also search for rate-compatible punctured convolutional codes which can be used for two-level unequal error protection (UEP) of digital audio. Since some of the tones in the multitone modem (OFDM) are more exposed to interference than others, optimal assignments of convolutional code bits to tones depending on their spectral position are also found. A large number of new codes with memory 6 and 8 are presented both for equal error protection and UEP.     

采用COSTAS环路的全制式音视频IF锁相环设计

一种能解决全电视制式的音视频锁相环设计,在I2C总线控制下与AFC(数字自动频率控制)相配合,完成了视频信号与音频信号的快速捕捉锁定与实时追踪,解决了调谐器需要人为操控完成制式转换的问题。文章详细阐述了完整设计过程,解决了模块级设计、仿真验证与版图设计中的关键技术。该设计的电路模块包括偏置电路及其启动电路、基准电压源、FPLL检波器、压控振荡器、窄带FM-PLL、Nf频率合成器、数字AFC、I2C总线控制器等。并对模拟乘法器、COSTAS环鉴频辅助器、VCO振荡控制范围及低噪设计、窄带PD等功能以及完整系统,采用Spectre仿真器进行了仿真验证。电路设计兼顾双极模拟电路与数字电路的优点,电路结构设计充分考虑了应用兼容性,并在音视频信噪比、锁相精度等多项性能指标上有了很大提高,使用外围简单且操作灵活。     

Low cost video scaler and gray scale integrator

A hybrid digital/analog device capable of making high-resolution linear and area measurements from a standard monochromatic video image is described. The device is capable of dynamic as well as static data acquisition when used in conjunction with standard NTSC video recording equipment. Digital output allows for computer interfacing. Linear dimensions are obtained by electronically superimposing two horizontal and two vertical scaling lines on a video monitor. Each linear dimension has an eight-bit resolution and is displayed on the front panel with seven segment LEDs. Eight-bit, digital-to-analog converters are also used to provide analog outputs. A measurement of the temporal deformation pattern of the accessory capsule surrounding a mechanoreceptor (Pacinian corpuscles) in response to vibratory displacements is demonstrated. Area measurements are obtained via a window comparator, a 6 MHz clock, and a 16-bit digital-to-analog converter. Data is only valid within the zone set by the scaling lines, allowing data regions to be isolated from noise, etc. The 16-bit digital signal measuring the area of interest is then converted for analog output. The measurement of the consensual pupillary reflex in response to full-field illumination (Ganzfeld) is given as an example     

Analog Data Recording with a Video Cassette Recorder

A multichannel, analog data storage system is presented which utilizes a compact video cassette recorder. Typical video cassette recorders operate at 3?ips and consequently allow up to one hour of continuous recording. The rotary two-head, helical-scan system employed yields a relative head-to-tape speed of 404.3 ips and a bandwidth of 3 to 4 MHz. The analog recording system described herein consists of an encoder which multiplexes and digitizes eight analog signals, a video recorder for storage of the digital data, and a decoder which demultiplexes and recovers the analog information. One unique feature of this system is that digital words which are generated consist of the channel number as well as the analog information present on that channel at the time of sampling. All information is combined serially and recorded with each word uniquely separated by a special "sync pulse." Another system feature is the ability to individually select the data bandwidth of each analog channel from values between approximately 25 kHz to 3 Hz. Design, fabrication, and evaluation is given. Interfacing to computing systems and microprocessors is discussed. An eight channel system with eight bit data words is described yielding approximately one-half percent resolution. However, the system is readily expandable to any number of channels and up to 16 bit data words yielding more resolution or higher signal-to-noise ratio.