Bandwidth and storage for CCTV

The amount of bandwidth used by a CCTV camera is directly proportional to the video quality. The higher the quality, the higher the transmission bandwidth and also the need for storage space.

I will talk about the factors that influence image quality and the use of bandwidth for transmission and amount of storage necessary for CCTV:

Factors to consider

1. Image resolution

2. Frame rate (frames per second)

3. Compression algorithm

4. Scene activity (movement)

5Continuous or event recording

Bandwidth for CCTV

I will talk about the factors that influence image quality and the use of bandwidth for transmission and amount of storage necessary for CCTV:

IMAGE RESOLUTION

It is basically the size of the image that is measured in pixels. In CCTV there are different resolutions such as: CIF, 2 CIF, 4CIF, D1, VGA, SVGA, etc.

These nomenclatures are not very common for the end user who are familiar with more popular resolutions such as: HD, Full HD, Mega Pixel and 4K.

It is possible, for example, to have cable TV with HD resolution or watch a Blu-Ray movie with Full HD resolution. It is also common to see cameras that take pictures with mega pixel resolution and TVs with 4K resolution .

When you talk with your customer about resolution, the best way is to use the nomenclatures that he knows and is part of his day-to-day life, you can also compare with the devices that he uses.

So you can offer cameras and recording systems with DVD quality (4CIF), or quality cable TV (HD) or Blu-Ray (Full HD) quality. This way it is much easier for the customer to understand what you are talking about.

4K resolution for CCTV

FRAME RATE

The number of recorder frames per second determines whether the image has a continuity (fluidity) aspect has more "robotic".

The principle of a video is to have many images being displayed in a quick sequence, the larger the amount of images displayed over a period of time, the better the sense of continuous motion. Images displayed at 30 FPS (Frames Per Second) appear to be more continuous than 15 or 10 FPS images, however the consequence of having higher frame rate per second is greater bandwidth and storage usage,

For a CCTV system values like 15 FPS are most commonly used in the recorder settings, however depending on the needs of the project you can use higher or lower values.

The frame rate per second will vary by project, but consider using 15 FPS for most projects.

Frames per second (FPS) affects the image fluidity

Higher frame rate results in less robotization

The frame rate per second will vary by project, but consider using 15 FPS for most projects.

COMPRESSION ALGORITHM (CODEC)

It is a mathematical algorithm that reduces the amount of bandwidth and storage required to carry and store the video respectively.

The video when captured is too large to be transported and stored, so it is necessary to compress it and for that, there is a compression algorithms that can be more or less efficient. Such algorithms have evolved in CCTV from MJPEG to MPEG-4 and to the current H.264 and H.265.

Although there are other compression formats such as JPEG-2000 among others in CCTV the most famous and currently used is the H.264 that works with prediction, color variations and movements providing bandwidth savings and storage according to complexity and activity of the scene.

There is also the new H.265 that is an improvement of the H.264. Besides the fact that this new algorithm can improve the video compression, it uses a lot of CPU power. 

As a general rule, you can now consider purchasing and using equipment with the H.264 CODEC for most of the CCTV projects.

==> To learn more, read the article: How CCTV codecs work.



CODEC for CCTV

SCENE ACTIVITY (MOVEMENT)

It is the variation of the movement in front of a camera, that determines if the sequence of images is simple or complex.

The amount of movement varies greatly from one environment to another, according to this variation, the camera will have to process and send more information, ie in a situation where few people or vehicles pass in the field of view of the camera, there is not much information for the camera to process, because without the variation of the scene, the images become simpler and cost less in terms of the resources to transmit and store.

In environments such as residences and small offices the variation of scene is generally small, in commercial places such as stores, malls and airports the activity is much more intense, so the variation of movement is medium to high.

As a general rule for projects, always consider the activity of the scene with a margin of safety, in commercial areas for example, the activity will be intense. So for the calculations consider as a medium or high activity.

Scene activity

CONTINUOS OR EVENT RECORDING

It is the way videos are recorded considering the length of time, it can be recorded 100% of the time even when there are no movements or recording takes place only when there are motion alarms (or other types of alarms) generated by the camera.

A camera can work with different types of events that include motion detection when a person or object passes in front of the camera, events generated by sensors connected to the camera or even by intelligent analysis of modern IP cameras.

When working with events, it is possible to record on a digital video recorder that will store the videos only for the specific period generated by the alarm, in order to perform a more efficient recording that uses less storage space and provides easier searching.

The use of continuous or event recording varies depending on the installation of each camera, but for the purposes of projects, in most cases consider event recording at the time of the calculations

==> Did you know there is a free surveillance software that can save you bandwidth ? To learn more, read the article: Luxriot Evo VMS: How to save IP cameras bandwidth.

Want to learn more ? 

If you want to become a professional CCTV installer or designer, take a look at the material available in the blog. Just click the links below:

Ultimate Guide V3

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