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The Ins and Outs of H.264

Orginal article by Steve Carney on Tue, Sep 18, 2012 @ 02:15 PM. New developments in technology often present related challenges that need to be overcome, all part of the give and take environment of progress. The rapidly evolving IP cameraarena is not immune to this, and one challenge that has emerged is the complexities of the H.264 compression standard. As the pixel count in IP cameras grows, so does the need to tap into the variety of techniques H.264 offers.

Rather than relying on the vague low, medium and high settings associated with MPEG-4 and MJPEG, H.264 offers techniques that far exceed previous compression models but, in turn, requires more knowledge of what they are and how they work.

One of the first things to consider in selecting an HD or megapixel camera is the H.264 profile used by the device, and weighing that feature with how the camera will ultimately be used. Is the goal to provide a crisp and clear image of a bank or pharmacy robber? Or is the goal to tap into the benefits of reduced bandwidth consumption?

If the purpose is a lower-cost installation where performance isn’t the primary consideration, it’s possible to get by with a base profile, which was developed for low-complexity applications and lacks the flexibility of motion prediction models.

If the goal is to meet the needs of standard resolution transmission, than using H.264 main profile is a viable option. It offers a motion prediction model that speeds encoding within the camera, and is also more effective in compressing interlaced images.

But if the focus is on HD and megapixel applications, than the clear choice is a camera using the H.264 high profile. This profile was designed for HD video encoding and decoding, and can process more bits as well as add the color depth associated with Blu-ray-quality video. It is also commonly used in streaming video for YouTube and the iTunes store, for example.

Another factor to consider in the IP camera scenario as it relates to H.264 is the bit rate setting. Again, there are three options: variable bit rate (VBR), constant bit rate (CBR) and constrained variable bit rate (CVBR).

VBR offers the least precise option for CCTV professionals because of its inherent vagueness among the five settings and the quantization parameter, or QP value, tied to each of them. As a result, many camera makers are moving away from this option and going with CBR as their main or only option.

CBR allows users to set a specific bit rate as a maximum. And even though the camera may not produce to that level, it won’t ever exceed it. The downside here is that it can lead to the purchase of more storage than necessary.

CBVR, which allows a user to set a maximum data rate and the minimum a camera could produce, is currently the least used option among the three, but offers the most control and ability to predict storage needs.

The market will continue to migrate towards IP cameras and, as a security professional, it’s important to know your performance goals and cost parameters. With this information in hand, you will be able to identify and dictate the correct H.264 profile and bit rate for your security video installation.

Interested in more details on deploying H.264? Click here to download an informational white paper on utilizing the H.264 compression standard.

  • by tansal
  • posted at 1:06 pm
  • February 17, 2013

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