Glossary

There is only one time, which is UTC 0 time at GMT. all the other times are translated time according to their time zones.  

[NVR]
So when an event or an incident is recorded in NVR, it is very important to make sure that the recorded images are synchronized to the correct time.
DirectIP NVRs use SNTP(Simple Network Timesync Protocol) to synchronize its time to a master time server or can run as a SNTP server to which the time of other NVRs can be synchronized.

[Camera]

When the analog cameras were first invented, we did not have enough technologies to handle bandwidth of D1@30ips full frame. So instead, the early engineers use a technique called interlaced video signal, used in NTSC/PAL, to use time and inter line multiplexing. So the story goes to complicate the old analog camera field image vs frame image, and even/odd fields, giving interlacing zig-zag artifacts of moving objects.
Virtually all IP cameras including DIP cameras use progressive scan these days. all images are taken in a progressive way.
However, in most cases, the image sensors use rolling electronic shutter, not a global electronic shutter. It's not perfect, but it is so much better than the interlaced scanned video.

Image cropping refers to remove of the outer parts of an image depending on the application.

1080p and 720p and 4CIF all have different aspect ratios, and often 1080p IP cameras use cropping for 720p video stream. But this result in different field of view.

DIP cameras use scaling to deal with these different aspect ratios. Instead of cropping out the images, it scales and streches the images maintaining the same field of view regardless of the resolution used.

Extremely wide angle lenses ranging from 180~360 degree. The raw images are warped into a circle.
You can record these raw video and the use dewarping software do dewarp the video on the fly.

DirectIP cameras talk to DirecIP NVRs using DirectIP protocol. They can discover each other on the same subnet automatically. This is called auto scanning. No IP address, subnet mask, gate way information settings are required for each IP cameras, which is a big time saving during the installation.

Bit rate is a little bit controversial. the codec engine is the game of using less bit rate for the equal or better video image quality. given the same codec profile, the bit rate roughly translates into the amount of information about the video image quality allowed to reconstruct the video image.
A reasonable and optimized bit rate is used in most IP camera codec engines. but sometimes, you meet an application that requires a lot higher fidelity. You can tackle it with higher mega pixel cameras, or you can tackle it with higher bit rates.

In DirectIP product, we use basic~very high quality that use bit rates optimized for most video surveillance applications. And 12Mbps@1080p@30IPS is one of the best that you will find.

codec comes in different capabilities. a profile is a collection of techniques used in a codec engine. the more sophisticated  techniques are used, the higher compression efficiency, and the better codec profile with different bit rate. in H.264, typically base profile is used in lower cost codec engines, and main profile or high profile is used for more high end IP cameras.

IP camera can compress video images in more than one codec, such as H.264 and MJPEG.

IP camera provides multiple video streams, probably, in multiple video profile.

IP video stream that NVR can subscribe to do live watching or recording

Codec specification of the video: resolution, ips(image per second) and bit rate.

Lens format is the focal plane size of the lens. You can use 1/2" format lens for smaller image sensors, such as 1/2.7" or 1/3" or 1/4", but not the other way around. Or else, you will end up seeing part of the lens barrel shadows at the corners of the image especially in wide angle mode.

Optics play a very important role in cameras. And good lenses are critical to build a good surveillance system. When we talk about resolutions, we often talk about image sensor resolutions but not the one for the lenses. Your image is going to be only as good and sharp as the capability of the lens that you use in your camera. Mega pixel lenses can "resolve" mega pixel resolutions on its focal plane.
You can use analog camera lenses on mega pixel cameras. You will see the images, but they will never be mega pixel sharp, but blurry no matter how hard you want to focus it because the lens you are using can not resolve more than about D1 resolution, not mega pixel resolutions.

Infrared LEDs are used to illuminate low light scenes. Typically they are 850nm (visible to most human), and non visible 920nm.

If you are using IR illumination in your scene, make sure you use an IR corrected lens on your camera, if not you will experience focus drift if your lens is not IR corrected and when only the IR LED lights are used. IR corrected lens allows the IR lights to focus on the same focal plane as the visible lights.

Instead of ICR, it uses a IR pass filter which passes the visible spectrum of lights as well. It works great in artificial light conditions, such as indoor applications, but when you have light sources that emits IR spectrum, such as incandescent light blurs, halogen or sun light, the color can be slightly distorted.
Because it is less complex to build the camera without ICR, it is more affordable than True Day and Night cameras.

Infrared Cut-filter Removal is a mechanism used in True Day and Night cameras. Camera sensors are sensitive to a wider spectrum of lights the spectrum of visible lights. So it can see what you can not see. During the day time, it puts the IR cut filter between the lens and the image sensor in True Day and Night cameras. Without this filter, the sensors will see the non visible lights, and may distort the colors on the scene or blur the scene. Also, Frequently Infrared LED lighting is used to assist to low light conditions. So the IR cut filter is removed during the night time so that the IR LED light source can be used to sense the scene in IR spectrum. Because human eyes can not see the IR, the scene is rendered in black and white.