If you are responsible for planning or designing a new CCTV video surveillance system, you have to make a technology choice regarding which video compression technique to use.
For sure, it will be digital. But which video compression scheme is the most suitable for your application?
1. Motion JPEG CCTV video compression
The JPEG standard was developed by the Joint Photographic Expert Group (part of ISO) for efficient storage of individual frames. Motion JPEG or M-JPEG is a series of separate JPEG images that form a video sequence. When 16 JPEG image frames or more are joined together per second, the result is an illusion of motion video. Video reproduction at 30 frames per second (FPS) for NTSC signals or 25 FPS for PAL signals is called full motion video or continuous-motion video.
Although Motion JPEG is an unlicensed standard it is widely compatible with many applications that require low frame rates or technologies such as Video Analytics where frame by frame analysis is crucial.
Advantages
1. Ability to support multi-mega pixel resolution.
2. Ideal for courtroom single frame evidence.
3. Clearer images at lower frame rates than MPEG-4.
4. Frame by frame playback offers more frames to view.
5. Technology is simpler; this can reduce the cost of a camera or video codec.
6. At low bandwidth priority is given to Image Resolution.
Disadvantages
1. High bit rate for scenes with little or no activity increases bandwidth and storage.
2. Video quality deteriorates at higher compression ratios.
3. No M-JPEG standard often means incompatibility issues.
4. Converting M-JPEG into another format reduces video quality.
5. Dated technology superseded by more bandwidth-efficient encoding techniques.
MPEG-4 CCTV video compression
MPEG-4 is a compression standard that was introduced in late 1998 by the Moving Picture Experts Group. In video surveillance applications MPEG-4 Part 2, also known as MPEG-4 Visual is the version of MPEG-4 most commonly used. MPEG-4 supports both low-bandwidth applications and those applications that require high quality images, with virtually unlimited bandwidth and no limitations in frame-rate. Typically most MPEG-4 based encoders and cameras support video up to DVD quality.
MPEG-4 is much more efficient than M-JPEG because video frames are analysed prior to being sent across the network. The first compressed image (I frame) is used as a reference point, the following images only contain information that differs to the initial I frame reference image. Periodically I frames are transmitted within the video sequence to ensure a recent reference point. The distance between these I frames is known as the GOP (Group of Pictures). The distance between I frames is usually user definable depending on the application and activity in the scene. For example a 25 FPS video stream with a GOP of 50 would mean a new I frame with GOP change information is sent every 2 seconds. The viewing application on the receiving end of the transmission then reconstructs all images based on this information and displays the video.
Advantages
1. MPEG-4 up to 5 times more efficient than M-JPEG at low bandwidths.
2. Increases the amount of time video can be stored compared with M-JPEG.
3. Uses less network bandwidth when compared with M-JPEG.
4. Very efficient at high frame rates.
Disadvantages
1. When the bit-rate is limited video quality suffers.
2. Low efficiency at very low frame-rates or extremely high scene activity.
3. Can be liable to “blurring” on freeze frame or very high motion.
H.264 CCTV video compression
H.264 is the latest MPEG standard for video encoding that is geared to take video beyond the realms of DVD quality by supporting Hi Definition CCTV video. H.264 can also reduce the size of digital video by more than 80% compared with M-JPEG and as much as 50% with MPEG-4, all without compromising image quality. This means that much less network bandwidth and storage space are required. Since the typical storage costs for surveillance projects represent between 20 and 30 percent of the project cost significant savings can be made.
Like many sectors of our industry, the devil is in the detail and system integrators and end-users who wish to see the benefits of an IP-based solution should look to someone who really knows the technology and can give an impartial view. It is common sense that manufacturers will only support their own hardware and will promise the earth for it, whereas a distributor will have evaluated a number of solutions from different vendors and be able to say that product A is the best for solution B because of XYZ whereas product Y is the best for solution C because of etc etc.
Advantage
1. H.264 cameras is that they reduce the amount of bandwidth needed.if your megapixel camera needed 10 Mb/s before (with MJPEG), it might now need only 1.5 Mb/s. So for each camera, you will save a lot of bandwidth.
2. Eliminates barriers: Enables many more networks to support megapixel cameras.
3. The bitstream is fully compatible with existing decoders with no error/drift.
Disadvantages
1. Using analytics with these cameras reduces the H.264 benefit.
2. Costs few hundred dollars more per camera.
For sure, it will be digital. But which video compression scheme is the most suitable for your application?
1. Motion JPEG CCTV video compression
The JPEG standard was developed by the Joint Photographic Expert Group (part of ISO) for efficient storage of individual frames. Motion JPEG or M-JPEG is a series of separate JPEG images that form a video sequence. When 16 JPEG image frames or more are joined together per second, the result is an illusion of motion video. Video reproduction at 30 frames per second (FPS) for NTSC signals or 25 FPS for PAL signals is called full motion video or continuous-motion video.
Although Motion JPEG is an unlicensed standard it is widely compatible with many applications that require low frame rates or technologies such as Video Analytics where frame by frame analysis is crucial.
Advantages
1. Ability to support multi-mega pixel resolution.
2. Ideal for courtroom single frame evidence.
3. Clearer images at lower frame rates than MPEG-4.
4. Frame by frame playback offers more frames to view.
5. Technology is simpler; this can reduce the cost of a camera or video codec.
6. At low bandwidth priority is given to Image Resolution.
Disadvantages
1. High bit rate for scenes with little or no activity increases bandwidth and storage.
2. Video quality deteriorates at higher compression ratios.
3. No M-JPEG standard often means incompatibility issues.
4. Converting M-JPEG into another format reduces video quality.
5. Dated technology superseded by more bandwidth-efficient encoding techniques.
MPEG-4 CCTV video compression
MPEG-4 is a compression standard that was introduced in late 1998 by the Moving Picture Experts Group. In video surveillance applications MPEG-4 Part 2, also known as MPEG-4 Visual is the version of MPEG-4 most commonly used. MPEG-4 supports both low-bandwidth applications and those applications that require high quality images, with virtually unlimited bandwidth and no limitations in frame-rate. Typically most MPEG-4 based encoders and cameras support video up to DVD quality.
MPEG-4 is much more efficient than M-JPEG because video frames are analysed prior to being sent across the network. The first compressed image (I frame) is used as a reference point, the following images only contain information that differs to the initial I frame reference image. Periodically I frames are transmitted within the video sequence to ensure a recent reference point. The distance between these I frames is known as the GOP (Group of Pictures). The distance between I frames is usually user definable depending on the application and activity in the scene. For example a 25 FPS video stream with a GOP of 50 would mean a new I frame with GOP change information is sent every 2 seconds. The viewing application on the receiving end of the transmission then reconstructs all images based on this information and displays the video.
Advantages
1. MPEG-4 up to 5 times more efficient than M-JPEG at low bandwidths.
2. Increases the amount of time video can be stored compared with M-JPEG.
3. Uses less network bandwidth when compared with M-JPEG.
4. Very efficient at high frame rates.
Disadvantages
1. When the bit-rate is limited video quality suffers.
2. Low efficiency at very low frame-rates or extremely high scene activity.
3. Can be liable to “blurring” on freeze frame or very high motion.
H.264 CCTV video compression
H.264 is the latest MPEG standard for video encoding that is geared to take video beyond the realms of DVD quality by supporting Hi Definition CCTV video. H.264 can also reduce the size of digital video by more than 80% compared with M-JPEG and as much as 50% with MPEG-4, all without compromising image quality. This means that much less network bandwidth and storage space are required. Since the typical storage costs for surveillance projects represent between 20 and 30 percent of the project cost significant savings can be made.
Like many sectors of our industry, the devil is in the detail and system integrators and end-users who wish to see the benefits of an IP-based solution should look to someone who really knows the technology and can give an impartial view. It is common sense that manufacturers will only support their own hardware and will promise the earth for it, whereas a distributor will have evaluated a number of solutions from different vendors and be able to say that product A is the best for solution B because of XYZ whereas product Y is the best for solution C because of etc etc.
Advantage
1. H.264 cameras is that they reduce the amount of bandwidth needed.if your megapixel camera needed 10 Mb/s before (with MJPEG), it might now need only 1.5 Mb/s. So for each camera, you will save a lot of bandwidth.
2. Eliminates barriers: Enables many more networks to support megapixel cameras.
3. The bitstream is fully compatible with existing decoders with no error/drift.
Disadvantages
1. Using analytics with these cameras reduces the H.264 benefit.
2. Costs few hundred dollars more per camera.