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

Video Surveillance Hard Drive Size Statistics 2018 on Nov 08, 2018
What is the most common hard drive size for video surveillance? 150+ integrators answered: What size hard drive do you most commonly use? What...
Kogniz Silicon Valley AI Startup Profile on Nov 07, 2018
Kogniz is a Silicon Valley company that aims to bring AI analytics to security and surveillance, centering on their own smart cameras: We spoke...
Dahua Dual Imager Dome Camera Tested (HDBW4231FN-E2-M) on Nov 07, 2018
Dahua has introduced a dual-imager dome model, the HDBW4231FN-E2-M, with two independently positionable sensors including integrated IR, not found...
Favorite Video Surveillance Hard Drive Manufacturer 2018 on Nov 06, 2018
Who is the favorite hard drive for video surveillance use? 150+ integrators answered: What is your preferred brand/model of hard drive for...
Winter 2019 IP Networking Course on Nov 05, 2018
This is the only networking course designed specifically for video surveillance professionals.  Lots of network training exists but none of it...
Video Surveillance Hard Drive Failure Statistics 2018 on Nov 02, 2018
Hard drive failures can be significant service problems but how common of an issue are they in video surveillance? How long do drives last when...
Building Occupancy Codes and Access Control Tutorial on Nov 01, 2018
A building or room's classification can greatly impact which building codes must be followed. In terms of access control, these 'occupancy codes'...
Cloud Video Storage Usage 2018 on Oct 31, 2018
Storing email and documents in the cloud have long been common, with on-site email or file servers increasingly eliminated. However, what about...
Video Quality / Compression Tutorial on Oct 17, 2018
While CODECs, like H.264, H.265, and MJPEG, get a lot of attention, a camera's 'quality' or compression setting has a big impact on overall...
IACP 2018 Police Show Final Report on Oct 08, 2018
IPVM went to Orlando to cover the 2018 IACP conference, the country's largest police show (about as big as ASIS), examining the 700+...

Most Recent Industry Reports

'Sticker' Surveillance Camera Developed (CSEM Witness) on Nov 16, 2018
The Swiss Center for Electronics and Microtechnology (CSEM) has announced what it calls the: world’s first fully autonomous camera that can be...
ISC East 2018 Mini-Show Final Report on Nov 16, 2018
This is our second (updated) and final show report from ISC East. ISC East, by its own admission, is not a national or international show, billed...
Facial Detection Tested on Nov 16, 2018
Facial detection and recognition are increasingly offered by video surveillance manufacturers. Facial detection detects faces in an image/video...
Throughtek P2P/Cloud Solution Profile on Nov 15, 2018
Many IoT manufacturers either do not have the capabilities or the interest to develop their own cloud management software for their devices....
ASIS Offering Custom Research For Manufacturers on Nov 15, 2018
Manufacturers often want to know what industry people think about trends and, in particular, the segments and product they offer.  ASIS and its...
Hikvision Silent on "Bad Architectural Practices" Cybersecurity Report on Nov 14, 2018
A 'significant vulnerability was found in Hikvision cameras' by VDOO, a startup cybersecurity specialist. Hikvision has fixed the specific...
French Government Threatens School with $1.7M Fine For “Excessive Video Surveillance” on Nov 14, 2018
The French government has notified a high-profile Paris coding academy that it risks a fine of up to 1.5 million euros (about $1.7m) if it...
Integrator Credit Card Alternative Divvy on Nov 13, 2018
Most security integrators are small businesses but large enough that they have various employees that need to be able to expense various charges as...
Directory of Video Intercoms on Nov 13, 2018
Video Intercoms, also known as Video Door-Phones or Video Entry Systems, have been growing in the past decade as more and more IP camera...
Beware Amazon Go Store Hype (Tested) on Nov 13, 2018
IPVM's trip to and testing of Amazon Go's San Francisco store shows a number of significant operational and economic issues that undermine the...

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