What is the Difference Between Dedicated NVR and PC-based VMS

If we look back about ten years ago, the graphic compression card was dominating the CCTV industry. In a typical CCTV system, it always had graphics card with PC computer, and all the coax cables were wired back to the graphic card. We almost can’t find this kind of application today. People use dedicated DVR/NVR instead of graphics card and PC-based DVR. The operation of dedicated DVR/NVR is simple as set-top box, barely require no technical skill to operate. However, the PC-based VMS (video management software) is still having strong market share. Both VMS and dedicated DVR/NVR can accomplish part of job which is similar, but they are not the same.

Recording-Playback-Live

Recording and playback footage, providing the live for real time monitoring is the basic function for all video surveillance system. Both VMS software and dedicated DVR/NVR can get these job down. The dedicated DVR/NVR is more effective with these functions. Single dedicated NVR can handle 128-channel 1080p IP cameras. If we employ VMS software, it could take several powerful PC computers working together to build the system. Plus license fee for cameras and windows OS, the total cost could be triple up. However, the VMS is more versatile than dedicated DVR/NVR, most of the dedicated don't even have quick playback which is the standard function in VMS software.

System Scale

The VMS is more suitable for middle or large security system. It is center-server (CS) software structure. All the IP cameras connect to a center server, and the core functions, such as recording, video regeneration, are processing at the center server. The operator can access the server with client software. It is easier to deploy distribution structure to manage and record over thousands cameras with VMS software. The dedicated DVR/NVR system requires each camera link to itself for recording and display. Those DVR/NVRs doesn't communicate with each other. Somehow it is more similar as many independent severs sitting on the desk. The operator needs to access each of the servers to search the footage. One of the solution is we can use NVR switch to manage multi NVRs on single station. It still doesn't put dedicated DVR/NVR to communicate with each other, but it improves the operator's accessing speed to each dedicated DVR/NVR unit.

Video Analysis

Video analysis is the weakness part for embedded DVR/NVR this moment. It is easy for VMS to perform the video analysis as long as PC server is powerful enough. Most dedicated NVR are still after cost-effective this moment, try to connect as much IP cameras as possible with maximize the CPU resource usage. I believe people will focus on video analysis in next step, especially the machine learning become mature. Training the NVR to classify the object could be a possible concept. For example, giving the NVR over millions different pictures of dogs, when the NVR receive a new pictures, it can tell it is a dog from otherwise. The direct way could just purchase the modeling feature from the supplier. What NVR need to do is grab the pixel from the image and compare with those existed feature.

H.265 or H.264

Dedicated NVR is leading this part now. Most of the VMS software is still doesn't support H.265 compression. If you connect an IP camera and set to H.265, normally, you see no video stream on the VMS. I don't think it is because H.265 is too complicated, it is only because H.265 is eating too much CPU resource and the conventional CPU still doesn't support hardware decoding. 

System Maintained

Technically, both systems have similar reliability. The dedicated NVR always employs embedded Linux, the system firmware is burnt to the ROM on board, and the user can not modify the core system. Most of the VMS is PC-based system, it require operation system such as the windows. Yes, we can put SSD and lock the OS driver, basically, it is similar as embedded PC, but still the general operation system is taking much CPU power for other features NVR doesn't require, running those services could generate more system maintained.

VMS delivers versatile functionalities, but it needs high cost and more maintenance. The dedicated NVR is simple, cost effective, and limited to basic surveillance purpose. We are seeing more and more function is adding to embedded NVR, such as dedicated NVR with LPR, fisheye VR. There are just not new for the VMS.

Should we choose TVI/AHD/CVI analog HD or IP when we upgrade our CCTV system?

People predicted the IP camera would replace analog camera very soon in few year ago. It seems the prediction is not so correct. The analog products are still showing the strong shipping today. To be fair, those HD analog are not the traditional technology which has limited resolution to 700tvl. The new analog technology, named TVI/AHD/CVI, can easily deliver 2 megapixel, even 4 megapixel resolution. What should we choose when we decide to upgrade our CCTV system? Let’s take a close look at the differences between those technologies.

The new analog camera TVI/AHD/CVI can deliver high definition video in the coax cable up to 300 meters. That means you can use your existed coax cable to carry the HD video when you upgrade the system. Simply replacing old cameras and DVR (recorder) can make the job done. It is important to understand the DVR need to be replaced. This is quick and fast way to transfer your analog to HD video system.

How about the video quality? If we put one analog HD camera and one IP camera on the same monitor, we will find the picture quality is not the same, even both cameras have same image sensors and resolution. The IP camera receives the raw video from the image sensor and encode to H.264/H.265 immediately. However the analog needs to travel among with coax cable before it reach the recorder. This process creates a lots of signal loss. We can find the significant differences especially when we look at the footage.

HD analog did have one advantage – live view without delay. The analog camera doesn't need to involve any encoding process, but the IP camera need to decode in the camera and encode at the NVR, you will experience 150-200 millisecond delay with IP camera before you see the video on the monitor screen.

One of the conclusions that analog system is much safer than IP camera system is not true. Both systems have the same security level. As long as the hacker make themselves enter your recorder (no matter DVR and NVR), they can retrieve the video easily.

What should we choose? It depends on the budget and the system scales. If it is the small system upgrade, like home surveillance system, employing HD analog is reasonable choice. You can replace the camera and recorder, reuse the existed coax. However, if it is the middle or large system, such as hotel, choose IP technology could save the total cost and business downtime. Image the owner just asks for some new cameras setup or relocate the existed cameras, analog structure always require point to point connection. You have to hard wire a coax cable from the camera to recorder which could generate serious business downtime and heavy labor cost. With network technologies, you can simple get the connection from the nearest switch and complete the job very soon. Besides, you also will impress your client with IP image quality.

Can we still reuse the coax to upgrade with IP video? Yes. The simple solution is the hybrid recorder. You can upgrade part of the cameras with HD analog cameras, and the rest with IP cameras. When the system expands, you start from the IP camera. Some of the VMS software is also available with hybrid input, like Exacq and Difgifort. The DVR can work as the encoder to convert the HD analog video to IP. In this case, the coax is reserved for analog HD camera.

As we mention above, the image quality of analog HD is not good as the IP. If the image quality is critical to your client, you can employ EOC (Ethernet over Coax) to send the IP video. All the coax can be converted into the cable which is suitable to carry the network signal. You can replace the traditional analog camera to new IP camera in all the installation point. The power even can be sent over the coax up to 250 meters. Basically, the coax will be turn into network cable with EOC.