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DVRs, or Digital Video Recorders, are devices which record video to a hard drive. The term Proprietary DVR refers to exclusive methodologies used to maintain commercial control over the DVR format and prevent third-party copying of a particular file. CCTV systems are used for the detection and recording of crime, but the analysts and law enforcement personnel who are required to obtain and process video recorded with proprietary DVRs may face problems using the proprietary format. Most established manufacturers will provide tools for law enforcement agencies to play and copy footage from such systems. The opposite of proprietary DVR is standard or PC-based DVR. (Although, in fact, many proprietary DVR's are PC-based devices.) Currently there is no standard output for the security industry to follow. Because of this, analysts are forced to obtain a compatible "player" in order to view the video. Some proprietary DVRs are delivered to the end-user in an executable player which allows for navigation. Some require the installation of the player. Others simply require a codec to be available on the system that is playing, then it will become viewable in a common player such as Windows Media Player. Some proprietary DVR systems offer more than one output format, such as the native format as well as a standard format such as AVI. Some also offer a composite video output PAL or NTSC. Some security companies are reluctant to offer anything other than their proprietary format. Reasons cited for maintaining control over the file by impeding conversion vary, but most companies will make "tamper resistance" a sellable feature, while disregarding the work required of an analyst or court in order to present the video. Another selling point of proprietary DVR systems is compression. Video compression removes information in exchange for a smaller file size. Increasing compression leads to the ability to store longer periods on a disk, at the expense of sacrificing some of the detail in the images. This trade-off must be considered when attempting to balance image quality and recording time in a DVR. As storage drives become cheaper and larger, compression sacrifices are improving. A problem inherent in proprietary DVR output is accuracy. There is a good chance that the video image as viewed has an incorrect aspect ratio and/or color information. Color may be off simply due to the calibration of the monitor being used, but often color information is not recorded accurately. It is not very common to white balance security cameras unless it is done at set up. Aspect ratios may also be recorded improperly and could actually be quite distorted. Aspect ratios on some players are sometimes user-adjustable by dragging the viewer in one direction or the other. Contrary to attempts made by proprietary DVR developers, it is possible to change virtually any DVR image into another format, but it cannot be done through digital conversion, such as changing an MPEG-2 to AVI. Instead it is done by intercepting the pixels sent by the proprietary DVR to the users monitor. There are a number of software available that will capture an area of a screen and generate an uncompressed file in a common format. Gradually technology is improving and DVR systems are capable of having features that analog video could never provide. One feature is the ability to store metadata, such as point of sale information. Another feature may be for an event (movement, panic button, door/drawer opening) to trigger a system to record at a higher resolution. Perhaps the greatest feature is the ability to navigate directly to an area of interest. ==See also== *Digital video recorder __noTOC__ 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Proprietary DVR」の詳細全文を読む スポンサード リンク
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