All security surveillance digital recording devices use some form of video compression to reduce the amount of storage required.
An uncompressed video signal requires 158Mbps for a standard definition video camera and much more for HD or Mega Pixel cameras. How the camera manufacture compresses this varies from brand to brand.
With H.264 being the most common compression in use, the implementation of it is not the same for all security camera manufactures. This is because H.264 is not a fixed compression standard. It is simply a set of tools that you can choose from to sample the video in different ways.
Confused?
Imagine you need to transport a large wooden antique cabinet from Australia to America but it needs to fit into 1 metre square boxes for transport. You can use as many as required. In your tool kit are common tools like hammers, screwdrivers and saws that everyone can use. Also in there are less common tools that require more skill and technique to use such as a plane and a set of chisels.
Company 1 chooses the quickest method that requires the least skilled staff to get the cabinet into the boxes. The 10 staff members use the hammer and screw driver to smash the cabinet into chunky pieces that fit in the boxes. Each box has a lot of wasted space and 100 boxes are required. When they reach America, one box had been lost. The cabinet was reassembled but as it roughly deconstructed, some of the parts don’t fit back together properly and others are missing. The end result is a cabinet but it looks terrible.
Company 2 has staff with a little more experience but as a result they also cost a little more. Their 10 staff carefully disassemble the cabinet using the hammers, screwdrivers and saws. Each part is cut to fit reasonably well into a box with minimal wasted space. They get the cabinet 90% packed before the courier arrives but have to rush to cut the lower parts to fit and as a result, the last few parts are a bit rough compared to the rest. Only 8 boxes were needed so the courier bill was cheaper. The reassembly looked quite good. There were a few visible lines where the parts had been cut but at the bottom where it had been rushed, it looked average.
Company 3 was made of a team of very skilled individuals with many years mastering their trades. They knew exactly how to pull the cabinet apart and by using the precision tools we able to ensure all the edges and fine detail were kept in good order. Additionally they had two teams working together. Team A did the top and team B did the bottom. Because they had twice as much man power and the skills, they were able to get the boxes packed neatly, avoiding wasted space and with enough time to book it on the early courier with no parts damaged or missing. They only needed to send 5 boxes, which made the courier happy because he could deliver some other customers orders at the same time. In America, the boxes arrived early and were able to be easily reassemble in a very short space of time. The cabinet looked awesome !
Now I am sure you have worked out the correlation of this story to video but just in case …
The trip from Australia to America is the network.
The workers are the compression algorithms running in the microprocessor. More people means faster results and having two teams is like dual processors resulting is a quicker delivery or less latency. The more skilled workers are the motion search algorithms the assess where savings can be made.
The Tools provide different motion search algorithms.
- A hammer is very basic and just smashes the video into chunks with little care for preserving the fine details.
- The screwdriver allows you to work on some of the finer details but is still quite rough for fine details.
- A saw allows you to cleanly slice the sections but with some tooth marks around the edges.
- Using a plane and chisel in addition to the above allows much finer detail to be preserved.
The boxes represent bandwidth and storage space. More boxes means more cost associated with transport and storage. Also the probability of loosing some in transport is increased. With less boxes, there is spare bandwidth and the IT department are happy.
So now that you are all experts in antique carpentry and transport, go and look more closely at how you camera or DVR compresses its video. Do you want:
- Great video image for 50% less bandwidth and no noticeable latency but often more expensive per camera.
- Video that is a little blocky when a person walks through the scene. May have low bandwidth but if it is a PTZ, sky rockets and the image quality drops and has latency issues.
- An image that is great if there is no activity in front of the camera but the bandwidth remains high all the time and the latency is terrible. But hey you saved some money.
The choice is yours.
