A CCTV DVR is a digital video recorder that is used for storing images and video from a CCTV camera. Different types of recorder are used for different types of CCTV system.
Types of CCTV Recorders
CCTV systems work best when the images produced by the camera are recorded. The system does not therefore require continually monitoring and can be used to provide footage for use at a later date for example as evidence in court.
Time-lapse CCTV Recorder
An out dated analog CCTV recorder that relies on tapes to record images. Playback is time consuming and requires that monitoring be stopped while recordings are viewed. Tapes must be regularly changed due to limited recording periods and must be replaced regularly.
PC Based CCTV Recorder
A PC can be used as a recorder for different types of CCTV system. For digital or HD systems an additional interface card and software package will be required. For IP CCTV no additional hardware is needed although monitoring and recording multiple cameras will require a CMS software package.
Set up can be complicated and with higher running costs home PCs are not designed for 24 hour continuous use which is usually required for CCTV. PCs are also often doing more than just monitoring CCTV which can cause conflicts and software problems meaning reliability cannot be guaranteed.
Professional Digital CCTV Recorder (DVR) (HD DVR)
A high resolution professional quality digital CCTV recorder available as a standard or high definition unit. Images are recorded onto a specially designed 24 hour hard drive which will continually overwrite footage when full. Recordings are stored from cameras of all types and footage can be viewed without interrupting recordings.
Playback is simple and the menu driven interface is often very user friendly. Most high end DVRs can connect to networks or the Internet. Recordings and live images can be viewed securely over the Internet on PCs or smart phones by multiple users. PTZ control and remote monitoring features are also included.
Mid Level DVR
Mid range DVRs have easy to use interfaces, hard drive recording and Internet connectivity. They offer playback and simultaneous recording and will record images at high resolution.
Hard drive management features mean footage is protected in the event of power interruption. Recording is usually available for up to 16 cameras.
Entry Level Domestic DVR
An entry level domestic DVR often records images at a lower resolution than that offered by the cameras and only has limited features. Some cannot playback footage while recording is in progress.
Images are recorded onto a hard drive for continuous recording, however power interruptions can potentially mean footage is lost due to hard drive management limitations and low cost hard drives not designed for 24 hour AV use.
Usually offer recording for 4 cameras.
Rack Mount Server Grade DVR
Highly specialised recorder capable of recording large numbers of cameras and offering a PC based interface for full control of an extensive range of features. These units are almost exclusively used for large commercial applications. Servers can be configured for digital and HD systems as well as IP CCTV systems.
NVR (Network Video Recorder)
An NVR is a recorder used for IP CCTV camera systems. Typically an NVR is doing a lot less work than a DVR found on a common CCTV system. This is due to the fact that settings and configuration are normally set in the camera with IP systems rather than globally in the recorder as with analogue/digital systems. The recorder will simply record the stream provided from the camera to one or more specialist hard drives. As viewing with an IP CCTV system is directly between the viewer and the camera the NVR will often have no monitor connection or configurable settings making them a simple and reliable part of an IP CCTV system.
Information about DVRs
Digital video recorders configured for physical security applications record video signals fromclosed circuit television cameras for detection and documentation purposes. Many are designed to record audio as well. DVRs have evolved into devices that are feature rich and provide services that exceed the simple recording of video images that was previously done through VCRs. A 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 can also be achieved by connecting the DVR to a LAN network or the internet. videoNEXT also makes a NVR surveillance application for the Mac OS X. Some of the latest professional digital video recorders include video analytics firmware, to enable functionality such as 'virtual tripwire' or even the detection of abandoned objects on the scene.
Security DVRs may be categorized as being either PC based or embedded. A PC based DVR’s architecture is a classical personal computer with video capture cards designed to capture video images. An embedded type DVR is specifically designed as a digital video recorder with its operating system and application software contained in firmware or read only 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.
- 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 1, 2, 4, 8, 16 and 32. Systems may be configured with a very large number of inputs by networking or bussing individual DVRs together.
- Looping video outputs for each input which duplicates the corresponding input video signal and connector type. These output signals are used by other video equipment such as matrix switchers, multiplexers, and video monitors.
- Controlled outputs to external video display monitors.
- Front panel switches and indicators that allow the various features of the machine to be controlled.
- Network connections consistent with the network type and utilized to control features of the recorder and to send and/or receive video signals.
- Connections to external control devices such as keyboards.
- A connection to external pan-tilt-zoom drives that position cameras.
- Internal CD, DVD, VCR devices 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.
Software features vary between manufacturers and may include but are not necessarily limited to
- 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 event.
- Compression methods determine quality of playback. H.264 hardware compression offers fast transfer rates over the internet 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.
- Routing of input video to video monitors based on user inputs or automatically on alarms or events.
- Input, time and date stamping.
- Alarm and event logging on appropriate video inputs.
- Alarm and event search.
- One or more sound recording channels.