CBR vs VBR: Surveillance Streaming

by John Honovich, IPVM posted on Jan 17, 2012 About John Contact John

How you stream video has a major impact on quality and bandwidth. Typically, when people think streaming or encoding, CODECs such as H.264, MPEG-4, etc come to mind. However, regardless of the CODEC, one still needs to choose how the video stream handles changes in scene complexity. This is where streaming modes such as CBR and VBR come into play. They have a major impact on quality and bandwidth consumption. In this report, we provide a tutorial and recommendation on how to optimially choose and use streaming modes.
CBR vs VBR
Choosing between CBR and VBR modes is typically overlooked:

• CBR stands for constant bit rate and like the term implies aims for a constant or unvarying bandwidth level
• VBR stands for variable bit rate and like that term implies allows the bit rate to vary

You need to determine whether and how much you will allow the bit rate levels to vary.
Why the Difference
What you are filming can vary dramatically in complexity:

• If you have a camera zoomed in on a white wall during the day, that is a very simple scene. For a 'good' quality level, a 720p HD / 30fps stream might need 200 Kb/s for this. 
• By contrast, if you have a camera aimed at a busy intersection, this is a very complex scene. At the same exact settings as the first scene, you might need 20x the amount of bandwidth, or 4,000 Kb/s to maintain the 'good' quality level.

The more complex the scene, the more bits (i.e., bandwidth) you need to maintain the same quality level. It does not matter how 'good' or 'advanced' your codec is, this will always be the case.


--출처 : http://ipvm.com/report/vbr_vs_cbr_surveillance_streaming