Initially I thought resolution and channels was all that mattered, so scoured eBay for a 8 Channel (to support unto 8 cameras) 960H DVR.
960H is the resolution, this is also known as WD1 (Wide D1) which is 960x576 pixels. This is the standard higher resolution CCTV system can record at. The other resolutions available are (in order of best to worst):
960H/WD1 - 960x576
D1 - 704x480
CIF - 352x240
QCIF 175x120
Now the camera generates 700TVL so feeding a recorder that records at 960H/WD1 will yield the best possible results.
If the DVR you are looking at records in only CIF/QCIF - stay well clear.
Next I looked at encoding formats, H264 is the standard nowadays, anything else (Mpeg4 etc) avoid!
Now things get a little confusing. Recording frame rates and resolution.
Just because the DVR on sale says "Full 960H WD1 High Resolution CCTV" dosnt mean it really is! The cheaper units (£50-£100) on eBay display live footage at the full 960H/WD1 resolution, but generally record at low CIF resolution.
You need to find a DVR that displays 960H live and records 960H!
Next up is frames per second. If you want your recorded footage to be smooth, your DVR must record at 25FPS (for PAL in the UK).
Not too complex right? Wrong!
Many DVR's at the lower end specify in their recording specs "Records at 960/WD1 at 1~25 FPS" this is very misleading. What does this actually mean?
Well it means that if you have one camera connected to the unit, it will record at 25FPS, if you have 2 cameras, each will record at 12.5FPS, 4 cameras 6.25fps, the full 8 cameras - a pathetic 3 FPS.
This is due to the low end slow CPU's in these budget units.
If the spec page for the DVR doesnt mention recording or mentions a variable for the FPS - stay away!
You want live 25FPS recording on EACH channel simultaneously. One way manufactures show this is the TOTAL FPS for the unit.
For example, an 8 channel unit that can record 25FPS on each channel would be a 200FPS unit (8x25FPS=200FPS).
If the unit you have in mind is for example a 8 channel unit rated at 125FPS. It is NOT true 25FPS recording per channel.
So we have covered resolution and FPS. Next is features.
A modern day DVR should have a gigabit ethernet port and allow access from anywhere in the world, even the budget low end ones allow this (although due to the slow CPU won't allow you to access remotely if its recording or record and play back at the same time).
You'll also want email notification - the system will mail you when it detects motion and starts to record. They pretty much all do this.
A RS-458 serial port? Yep, thats for connecting a PTZ camera to (Pan, Tilt, Zoom)
HDMI & VGA Out - to connect to your monitor or modern flat screen TV.
Composite out and audio out - In actual fact, yes! I will be running a simple low end composite feed to all the displays in the house, very handy for checking from another room.
Finally Audio. To start with audio in seemed pointless, the cameras don't have mics fitted. However, after reattach I discovered you can purchase small high gain mics that you can mount inside the cameras. Now I'm not going to have mics on all of them, but maybe it would be nice to have one on the front door camera, and in the future a mic on the camera in the babies room? So yes Audio in is needed. Many of the low end budget models don't have audio in at ALL. The slightly better models maybe have only 1 audio in.
You have a 8 camera system, but only 1 audio in, thats limiting.
So finally if you have a 8 Channel DVR, make sure it also has 8 Audio inputs. You'll only regret it later if you don't!
Finally storage!
Many units comes with hard drives, many come without. Id save yourself some money and buy one without a hard drive.
I have a 2TB SATA drive spare and will fit this to the system. Any drive size from 1TB up would be suited to approx 1 week of footage.
So in summary, I need a DVR that does at minimum the following:
-Record and Playback in 960H/WD1 resolution.
-8 Channels
-8 Audio Channels
-Gigabit ethernet
-Motion detect / record and notify by email
-200 FPS Giving 25FPS per channel
-RS-458 Serial port
-HDMI / VGA / Composite / Audio Out.
I have a DVR in mind, and am speaking to the supplier tomorrow. I will post again with my findings and hopefully purchase information!
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