Bruehs Walter E, Stout Dorothy
Federal Bureau of Investigation, Digital Forensic Analysis Unit, The Forensic Audio, Video and Image Analysis Program, Bldg 27958A, ERF-E, Quantico, VA, 22135.
Resolution Video Inc., 701 Kenmore Ave, Suite 103, Fredericksburg, VA, 22401.
J Forensic Sci. 2020 Jul;65(4):1155-1168. doi: 10.1111/1556-4029.14307. Epub 2020 Mar 5.
As the closed-circuit television (CCTV) security industry transitioned from analog media to digital video recorders (DVRs) with digital storage, the law enforcement community struggled with the means with which to collect the recordings. New guidelines needed to be established to determine the collection method which would be efficient as well as provide the best quality evidence from live DVRs. A test design was developed to measure, quantify, and rank the quality of acquisition methods used on live systems from DVRs typically used in digital CCTV systems. The purpose was to determine guidelines for acquiring the best quality video for investigative purposes. A test pattern which provided multiple quantifiable metrics for comparison between the methods of acquisition was used. The methods of acquisition included direct data download of the proprietary file and open file format as well as recording the video playback from the DVR via the available display monitor connections including the composite video, Video Graphics Array (VGA), and high-definition multimedia interface (HDMI). While some acquisition methods may provide the best quality evidence, other methods of acquisition are not to be discounted depending on the situation and need for efficiency. As an investigator that needs to retrieve video evidence from live digital CCTV systems, the proprietary file format, overall, provides the best quality evidence. However, depending on the circumstance and as recording technology continues to evolve, options other than the proprietary file format may provide quality that is equal to or greater than the proprietary file format.
随着闭路电视（CCTV）安全行业从模拟媒体过渡到具有数字存储功能的数字视频录像机（DVR），执法部门在收集录像的方式上遇到了困难。需要制定新的指导方针，以确定既高效又能从实时DVR中提供最佳质量证据的收集方法。开发了一种测试设计，用于测量、量化和排名数字CCTV系统中常用的DVR在实时系统上使用的采集方法的质量。目的是确定为调查目的获取最佳质量视频的指导方针。使用了一种测试模式，该模式提供了多个可量化指标，用于比较采集方法。采集方法包括直接下载专有文件和开放文件格式的数据，以及通过可用的显示监视器连接（包括复合视频、视频图形阵列（VGA）和高清多媒体接口（HDMI））从DVR录制视频回放。虽然某些采集方法可能提供最佳质量的证据，但根据情况和对效率的需求，其他采集方法也不应被忽视。作为一名需要从实时数字CCTV系统中检索视频证据的调查人员，总体而言，专有文件格式提供了最佳质量的证据。然而，根据具体情况以及随着录制技术的不断发展，专有文件格式以外的其他选项可能提供与专有文件格式相当或更高的质量。
