Introduction to Video CODECs : MJPEG, MPEG-4, H.264

Author: John Honovich, Published on Jun 13, 2008

CODECs are a critical element of choosing, designing and using video surveillance systems. CODECs can lower the price of overall systems and increase the usability of systems. As such, having a basic understanding of what a CODEC is and why CODECs are used is important.

Fundamental Principle of CODECs

The most important factor to understand in video CODECs is that CODECs help balance off different costs.

For instance, let's say you want to go to the mall and to the supermarket. A few years ago, when gas was cheaper, you might have done this in 2 separate trips. Now that gas prices have increased dramatically, you might want to combine those trips. What's happening here is that as gas has become more expensive, you are willing to trade off lower convenience for savings in cash.

Likewise, using CODECs is a balance between the cost of storage, bandwidth and CPUs. Specifically:

CODECs reduce the amount of bandwidth and storage needed at the expense of using more CPU cycles.

As such, selecting a CODEC always requires you to understand the tradeoffs in cost between using less bandwidth and storage or using less CPU cycles. Generally CPU cycles are cheaper than bandwidth and storage so more advance CODECs save you money. Sometimes, CODECs can be too demanding, especially with megapixel cameras and can potentially cost you more in CPU than you save in bandwidth and storage.

Please read our basic bandwidth tutorial for a review of it's impact on video surveillance.

CODECs Overview

Video must be digitized for it to be used and viewed on a computer. CODECs are means or choices in how we make the video digital.

CODECs or compression / decompression technologies are used to modify the video that is being digitized. Similar to how you might ZIP files on your PC, the video is compressed on its way into the computer. And just like with opening a ZIP file, the video is decompressed before you use or view the video. Unlike ZIP files, the compression of video losses some of the information (engineers refer to this as lossy compression). However, with the appropriate settings, a user cannot tell the difference visually.

Get Video Surveillance News In Your Inbox
Get Video Surveillance News In Your Inbox

Just like in the movies or TV, video is a series of images that are displayed rapidly one after the other. In the US, TV consists of displaying a series of 30 images per second. When we view these 30 images per second, it's “video” and it looks smooth. The fact that video is made up of a stream of images is quite important for understanding CODECs.

When you use a CODEC, you can compress the video in two fundamental ways:

  • Compress the individual image by itself
  • Compress a series of images together

When you compress an individual image by itself, you simply take the image, run the compression and output the saved file (technically called intraframe compression). Just like when you use Microsoft Paint and save as a JPEG, video compression of individual images works quite similarly. The difference with video is that you need to do these for a continuous stream of images. As such, rather than simply being a JPEG, it is called Motion JPEG or MJPEG.

The benefit of MJPEG is that it requires very low CPU use. The downside is that storage and bandwidth use can be quite high.

When you only compress an individual image, you ignore what's going on between multiple images in a sequence and often send redundant information. If you are streaming video at multiple frames per second, you often are sending basically the same image over and over again. This can be quite wasteful. It's similar to someone calling you up every minute to tell you nothing changed. It would be far better for the person to only call you when news occurred. You can simply assume during the rest of the time that the status is the same.

When people talk about the benefits of MPEG-4 and H.264, not sending repetitive information is the core source of their strength. Evey so often these CODECs will send a whole image (often called an i frame). The rest of the times they only send updates describing what parts of the image have changed (technically called interframe compression). Since it is common that large parts of the image remains the same, this can result in very significant reductions in storage and bandwidth. For example, where MJPEG may send image after image at 100 KB, codecs like MPEG-4 or H.264 may send the first image at 100 KB but the next 3 or 4 images at only 10 KB each. This can approach can reduce bandwidth and storage use by 50 – 90%.

The downside with this approach is that it takes more work for the computer to do this. When you are simply compressing individual images, you do not need to worry about what happened before or what the next image will contain. You simply apply the compression rule and execute. With MPEG-4 or H.264 you need to examine groups of images and make complex calculations of what changed and what did not. You can imagine this can become very complicated and consume lots of CPU resources.

H.264 and MPEG-4 are similar in that they both reduce bandwidth and storage by examining groups of images when they compress video. A key difference with H.264 is that it uses much more complex and sophisticated rules to do the compression. Because H.264's rules are more sophisticated, they can reduce bandwidth and storage even more than MPEG-4. However, the trade-off is that it takes more CPU cycles to do it.

Looking at Current Video Surveillance Systems

The general trend in video surveillance has been a continuous movement to CODECs that save bandwidth and storage. Historically, you have seen products move from MJPEG to MPEG-4 to H.264. The reason why this has happened is because the cost of CPUs to compress the video has decreased faster than the cost of bandwidth and storage. Most experts expect this trend to continue.

Recently, the biggest challenge using CODECs in video surveillance systems has occurred with the rise in megapixel cameras. For years, the maximum resolution of security cameras was constant.However, with megapixel cameras, the resolution of security cameras has increased by 400% or more. The greater the resolution, the harder the CPU needs to work and the more cycles that need to be allocated.

The huge increase in resolution is similar to the jump in gas prices. It has changed the economics of CODECs. Whereas historically, for standard definition security cameras, CPU cycles were cheaper than bandwidth and storage. Now, since so much more CPU cycles are needed, it can cost way more in CPU than what you save in bandwidth and storage. As such, most commercial megapixel cameras use MJPEG, especially if they are multi-megapixel (more than 1.3 MP).

One of the most important elements in the next few years will be the development of new approaches and use of new CPUs to reduce the cost of using H.264 for megapixel cameras. Much like alternative energy development hopes to bring the cost of energy down, new approaches are being sought to reduce the use of CPU cycles in compressing megapixel camera feeds.

Conclusion

Understanding the basic choices in CODECs and rationale for choosing CODECs is a key element in video surveillance systems. Please share your questions or feedback below.

Related Reports

Last Chance - Winter 2019 IP Networking Course on Jan 10, 2019
Today is the last day to register for the Winter 2019 IP Networking course. This is the only networking course designed specifically for video...
Managed Video Services UL 827B Examined on Jan 09, 2019
Historically, UL listings for central stations have been important, with UL 827 having widespread support. However, few central stations have...
H.265 / HEVC Codec Tutorial on Jan 08, 2019
H.265 support improved significantly in 2018, with H.265 camera/VMS compatibility increased compared to only a year ago, and most manufacturers...
Surveillance Codec Guide on Jan 03, 2019
Codecs are core to surveillance, with names like H.264, H.265, and MJPEG commonly cited. How do they work? Why should you use them? What issues may...
Camera Course January 2019 on Jan 03, 2019
This is the only independent surveillance camera course, based on in-depth product and technology testing. Lots of manufacturer training exists...
The Battle For The VSaaS Market Begins 2019 - Alarm.com, Arcules, Eagle Eye, OpenEye, Qumulex, Verkada, More on Jan 02, 2019
2019 will be the year that VSaaS finally becomes a real factor for professional video surveillance. While Video Surveillance as a Service (VSaaS)...
8MP / 4K Fixed Lens Camera Shootout - Dahua, Hikvision, TVT, Uniview on Dec 17, 2018
8MP / 4K fixed lens models are now common in lower cost lines, with nearly every Chinese brand and their OEMs now offering multiple options. To...
Cisco Meraki New Cameras and AI Analytics on Dec 14, 2018
Meraki has released their second generation of video surveillance with 3 new cameras, AI-based video analytics, and 2 cloud-based storage...
Ubiquiti $79 Flex IP Camera Tested on Dec 07, 2018
U.S. Manufacturer Ubiquiti has released a 1080p, integrated IR IP camera, selling it directly for $79, making this one of the least expensive IP...
Hanwha L Series Lowest-Cost Camera Tested on Dec 04, 2018
Hanwha has released their lowest-priced IP camera line ever, the L series, that competes on price with low cost competitors Dahua and...

Most Recent Industry Reports

Access Control Cabling Tutorial on Jan 15, 2019
Access Control is only as reliable as its cables. While this aspect lacks the sexiness of other components, it remains a vital part of every...
Gorilla Technology AI Provider, Raises $15 Million, Profiled on Jan 15, 2019
Gorilla Technology is a Taiwanese video analytics manufacturer that recently announced a $15 million investment from SBI Group, saying this...
2019 IP Networking Book Released on Jan 14, 2019
The new IP Networking Book 2019 is a 285 page in-depth guide that teaches you how IT and telecom technologies impact modern security...
Arecont Costar Layoffs on Jan 14, 2019
Arecont Vision, a Costar Company, has laid off more than 10% of their workforce in a move the company described to IPVM as a result of "important...
The False SCMP Story on Hikvision NYC AI on Jan 14, 2019
In the past week, one of Asia's largest publications, the South China Morning Post (SCMP), posted an article about "Chinese [facial recognition]...
WDR Tutorial on Jan 11, 2019
Understanding wide dynamic range (WDR) is critical to capturing high quality images in demanding conditions. However, with no real standards, any...
Pelco Favorability Results 2019 on Jan 11, 2019
Pelco had a significant favorability problem amongst integrators in our previous study (see 2016 Pelco results). Now, in the first edition of our...
Bad: Dahua Villa Video Doorbell Tested on Jan 11, 2019
Doorbells are one of the hottest segments in the residential market but Dahua's Villa Video Doorbell is the worst we have tested.   We bought and...
Last Chance - Winter 2019 IP Networking Course on Jan 10, 2019
Today is the last day to register for the Winter 2019 IP Networking course. This is the only networking course designed specifically for video...

The world's leading video surveillance information source, IPVM provides the best reporting, testing and training for 10,000+ members globally. Dedicated to independent and objective information, we uniquely refuse any and all advertisements, sponsorship and consulting from manufacturers.

About | FAQ | Contact