Let me explain the subtle differences amongst these two devices. Let’s begin by outlining the name structural.
DVR (Digital Video Recorder): An analog and/or IP based recorder is a consumer electronic device or application software that records video in a digital format to a disk drive, USB flash drive, SD memory card or other local or networked mass storage device. A digital video recorder configured for physical security applications record video signals from closed-circuit television cameras for detection and documentation purposes. Many are designed to record audio as well, whether at the camera or as a separate apparatus in an isolated area. DVRs have evolved into devices that are feature rich and provide options that exceed the simple task of recording video images that was previously done through VCRs. Any good DVR CCTV system provides a multitude of advanced functions over VCR technology including video searches by event, time, date and camera. There is also much more control over quality and frame rate allowing disk space usage to be optimized and the DVR can also be set to overwrite the oldest security footage should the disk become full. In some DVR security systems remote access to security footage using a PC, Smart Phone, or tablet can also be achieved by connecting the DVR to a LAN network that has an internet service. Some of the latest professional digital video recorders include video analytics software, to enable functionality such as ‘virtual alarm system’ or even the detection of differing objects on the scene. Security DVRs may be categorized as being either PC-based or a stand-alone unit. A PC-based DVR’s architecture is a classical personal computer with video cards designed to capture video images. A stand-alone DVR is specifically designed as a digital video recorder with its own operating system and application software contained in firmware or built in flash memory.
Hardware features of security DVRs vary between manufacturers and may include but are not necessarily limited to:
- Designed for rack mounting or desktop configurations.
- Front panel switches and indicators that allow the various features of the machine to be controlled.
- Connections to external control devices such as a mouse, keyboards, POS device, or PTZ controller.
- Controlled outputs to external video display monitors.
- Data ports for network connections consistent with the network type and utilized to control features of the recorder and to send and/or receive video signals.
- Internal optical drives or HDD’s typically for archiving video.
- Connections to external storage media.
- Alarm event inputs from external security detection devices, usually one per video input.
- Alarm event outputs from internal detection features such as motion detection or loss of video.
- Single or multiple video inputs with connector types consistent with the analogue or digital video provided such as coaxial cable, twisted pair or optical fiber cable. The most common number of inputs are 4, 8, 16 and 32. Looping video outputs for each input which duplicates the corresponding input video signal. These output signals are used by other video equipment such as matrix switchers, multiplexers, and/or an individual video monitor.
Software features vary between manufacturers and may include but are not necessarily limited to:
- Routing of input video to video monitors based on user inputs or automatically on alarms or events.
- Log filing of USERs, IP addresses, Input, time and date stamping.
- Alarm and event logging on appropriate video inputs.
- Alarm and event search.
- One or more sound recording channels. User selectable image capture rates either on an all input basis or input by input basis. The capture rate feature may be programmed to automatically adjust the capture rate on the occurrence of an external alarm or an internal event
- Selectable image resolution either on an all input basis or input by input basis. The image resolution feature may be programmed to automatically adjust the image resolution on the occurrence of an external alarm or an internal e vent.
- Compression methods determining the quality of playback. An H.264 hardware compression offers fast transfer rates over a data network with high quality video.
- Motion detection provided on an input by input basis, this feature detects motion in the total image or a user definable portion of the image and usually provides sensitivity settings. Detection causes an internal event that may be output to external equipment and/or be used to trigger changes in other internal features.
- Lack of motion detection. Provided on an input by input basis, this feature detects the movement of an object into the field of view and remaining still for a user definable time. Detection causes an internal event that may be output to external equipment and/or used to trigger changes in other internal features.
- Direction of motion detection. Provided on an input by input basis, this feature detects the direction of motion in the image that has been determined by the user as an unacceptable occurrence. Detection causes an internal event that may be output to external equipment and/or be used to trigger changes in other internal features. Such as a stationary camera being used as a trigger to tell a PTZ camera to look and focus in an area of interest based off of a preset you created.
NVR (Network Video Recorder): Unlike its predecessor, the DVR, a NVR is not limited to be in the same area as your cameras cabling to one section. The unit can be placed virtually anywhere, it simply just needs to be on the same LAN network as the IP based cameras. In terms, a network video recorder are distinct from digital video recorders as their input is assigned on a network rather than a direct connection to a video capture card. Video on a DVR is encoded and processed at the DVR, while video on an NVR is encoded and processed at the camera, then streamed to the NVR for storage or remote viewing. An NVR is a software program that records video in a digital format to a disk drive, USB flash drive, SD memory card or other mass storage device. An NVR contains no dedicated video capture hardware. However, the software is typically run on a dedicated device, usually with an embedded operating system.
NVR is used in IP video surveillance systems. Because of the nature of these units, a camera that is capable of capturing High Resolution (Mega Pixel cameras) will record and playback as that desired resolution unlike a DVR system. Hybrid DVR security systems exist which incorporate functions of both NVR and DVR.