在视音频切换器上加装视频自动切换报警电路

电视台播出电视信号时,常因为设备故障、自然气候影响或人为失误等原因造成加到发射机的图像信号衰落或中断。这对安全优质播出和发射设备的不良影响是不言而喻的。视频自动切换报警电路是在发生图像信号衰落或中断时能自动将视频输入切换到图像图形发生器所供信号(如彩条信号,测试卡;“信号中断请稍候”文字信号)上,以保持视音频切换器视频输出(即加到发射机的图像信号)的     

保证市级台安全播出的几项改革措施

目前市级电视台大部分都是人工切换进行播出的，在播出时为了防止按错切换器按钮或录像机按钮而造成播出事故，现根据我们实践经验自行设计、改装，增加“防止按错切换器按钮装置”和“录像机正播出时防止按镨其他按钮的装置”。此外在主切换器损坏无信号输出时，为了不中断播出立即倒换到备切换器播出，增加“主备切换器自动倒换装置”，还有把我台原机械式的继电器触点切换改装成电子切换，作为备切换器用。这些装置是保证安全播出的几项改革措施，是数字电路在播控中心的应用。     

谈2×1视频·音频自动切换器故障分析与维修

随着广播电视事业的发展,结合我台实际情况,新购进了四台南京陆朗VAAS—3型视频·音频自动切换器、六台音频立体声SAS—2003型自动切换器。这些自动切换器的使用,不仅大大的减轻了值班员的负担;而且因为主、备信号源之间可以自动切换(当主路信号中断时自动切换到备路信号,     

视频音频自动切换器

安全优质播出,是各级各类电视台的一项重要任务,本文介绍的视频音频自动切换器,可以满足一般电视台、站的实际要求。 1.基本框图该自动切换开关的基本电路框图如图1所示。它主要由视频检波、控制信号形成、视频切换开关、音频切换开关、报警信号发生器、视频分配和音频分配等部分组成。     

视频信号自动切换电路

前言在光纤视频传输中,为了实现不中断地可靠工作,发射机或接收机中常常设计有主通道或备份通道,一旦主通道发生故障机器便自动倒换备份通道工作。本文所叙述的是一个视频接收光端机视频信号自动切换电路。它可以切换一路视频信号,与继电器组合还可切换四路音频信号。它具有自动切换、自动复原、稳定可靠、易于装配调试的特点,可与各类视频、音频信号的模拟光端机或电端机相连接。     

一种新颖的视频预置切换器

一种新颖的视频预置切换器浙江衢州电视台范晓俊电视图象快切是节目播出中使用的主要手段，经过切换设备的切换衔接，才能将来自各种信号源的信号变成深受观众欢迎、丰富多彩的电视节目。近年来国内电视播出系统用得最多的是进口或国产的大中型特技切换机，性能较好。但对...     

CATV前端维修一法

信号短接法:CATV前端的信号流程由前向后,一般为:录像机或卫视接收机(信号源)→视音频分配器→视音频切换矩阵→视频图像插入器→调制器→混合器→宽带放大器→干线。其中的视音频分配器、视音频切换矩阵、视频图像插入器等设备,只是为改善信号质量和增加播控功能而使用的。在维修过程中,可利用视、音频电缆线,将流程中某设备短接的方     

如何提高有线电视播出信号的稳定性和可靠性——TL5431、TL5432视频音频处理器的应用

如何提高有线电视播出信号的稳定性和可靠性—ＴＬ５４３１、ＴＬ５４３２视频音频处理器的应用□刘致东（成都泰立广播电视研究所６１００４１）当前，许多中小有线电视台由于使用的设备技术水平不同，造成视音频播出信号的不稳定、不标准，图像时好时差，不稳定；声音时...     

中短波发射机激励信号自动切换器的设计与实现

在DF-100A型100kW短波发射机上安装一台备份激励器,并设计制作一款激励信号自动切换器,实现主、备用激励信号自动监测与快速切换功能,为安全播出提供更好的技术保障。     

实用的地面卫星接收防插播技术方案

卫星接收机在接收信号受到攻击或信号异常时,由于误码率激增,用于信号强度的指示器显示会出现大幅度衰落变化.设计了一块附加控制电路板,可以对卫星接收信号是否正常进行自动监控,信号受到攻击或信号异常时可自动切换信号,同时发出声光报警,攻击过后能自动恢复正常播出,从而实现收转卫星信号的安全播出与自动控制.     

Multiview video summarization using video partitioning and clustering

Multiview video summarization plays a crucial role in abstracting essential information form multiple videos of the same location and time. In this paper, we propose a new approach for the multiview summarization. The proposed approach uses the BIRCH clustering algorithm for the first time on the initial set of frames to get rid of the static and redundant. The work presents a new approach for shot boundary detection using frame similarity measures Jaccard and Dice. The algorithm performs effectively synchronized merging of keyframes from all camera-views to obtain the final summary. Extensive experimentation conducted on various datasets suggests that the proposed approach significantly outperforms most of the existing video summarization approaches. To state a few, a 1.5% improvement on video length reduction, 24.28% improvement in compression ratio, and 6.4% improvement in quality assessment ratio is observed on the lobby dataset.     

Constant quality video coding using video content analysis

In the literature, several rate control techniques have been proposed to aim at the optimal quality of digitally encoded video under given bit budget, channel rate and buffer size constraints. Typically, these approaches are group-of-picture (GOP) based. For longer, heterogeneous sequences, they become unacceptably complex or struggle with model mismatches. In this paper, an off-line segment-based rate control approach is proposed for controlling the distortion variation across successive shots of a video sequence when encoding with single-layer (MPEG-4 baseline, MPEG-4 AVC) and scalable (wavelet) video codecs. Consistent quality is achieved by optimally distributing the available bits among the different segments, based on efficient rate-distortion (R-D) modelling of each segment. The individual segments are defined based on shot segmentation and activity analysis techniques. The algorithm is formulated for three different distribution models: download, progressive download and streaming. The results indicate that the proposed technique improves the quality consistency significantly, while the processing overhead compared to classical two-pass variable bit-rate (VBR) encoding is limited.     

针对网络视频应用的视频转码技术综述

对视频转码的技术基础,尤其是3种典型的体系结构进行了简述和比较,然后讨论了利用从输入视频流中易于得到的信息,减少计算复杂度和改善视觉质量的方法。同时,对近年来出现的一些热点技术,如信息(包括水印和具有差错抑制特征的数据)嵌入的视频转码、H.264码流转码等进行了重点讨论。对视频转码技术的未来发展也进行了展望。     

Packet video

The 1990s will see a large increase in the use of video for many purposes, made possible through the use of new optical storage and transmission methods, as well as radio and satellite communication. HDTV, new broadcast services and 64 kbit/s ISDN video are all at an advanced stage of development. Digital methods of transmission and storage feature prominently in future scenarios of video usage. To avoid long delays in transmission, packet video techniques for storage of high-quality material on optical discs are being considered. Coded video signals can be transmitted in packet form at variable bit rate. The author discusses the principles of packet video. Packet loss, queueing delay and layered coding are discussed. The future developments are also discussed     

Digital video

Issues addressed at three Digital Systems Information Exchange meetings, held in November 1990 and March and September 1991, are summarized. The meetings explored digital developments, looked for areas of actual or potential commonality, and examined possible common frameworks for manipulating digital images. Progress in the area of digital video standards is discussed. The three main standards concern still-picture compression, video teleconferencing, and full-motion compression on digital storage media, Products being developed using standard digital video formats are surveyed. They include multimedia products, CD players, HDTV, and receivers     

A single-board video codec using video image signal processors

This paper discusses a newly developed single-board video codec using Video Image Signal Processors (VISPs). The codec has both a CCITT H.261 mode and a proprietary mode. Two VISPs, one for encoding and one for decoding, are used. The board size is 210 by 295 mm, the maximum frame rate is about 7.5 f/s, and the picture size is 180 by 144 pels.     

Blind video quality assessment based on multilevel video perception

Blind video quality assessment (VQA) metrics predict the quality of videos without the presence of reference videos. This paper proposes a new blind VQA model based on multilevel video perception, abbreviated as MVP. The model fuses three levels of video features occurring in natural video scenes to predict video quality: natural video statistics (NVS) features, global motion features and motion temporal correlation features. They represent video scene characteristics, video motion types, and video temporal correlation variations. In the process of motion feature extraction, motion compensation filtering video enhancement is adopted to highlight the motion characteristics of videos so as to improve the perceptual correlations of the video features. The experimental results on the LIVE and CSIQ video databases show that the predicted video scores of the new model are highly correlated with human perception and have low root mean square errors. MVP obviously outperforms state-of-art blind VQA metrics, and particularly demonstrates competitive performance even compared against top-performing full reference VQA metrics.     

基于视频解码器的图像卡设计

介绍了BT829B的主要特性，详细叙述了快速三维扫描系统中以BT829B为核心的图像采集系统的结构。