Axis P1244 User Manual page 17

AXIS P1244 Network Camera
Video
• Overlay settings. See About overlay text on page 20.
Click Save to apply the new settings.
H.264
H.264, also known as MPEG-4 Part 10/AVC, is a video compression standard that provides high quality video streams at low bit rates.
An H.264 video stream consists of different types of frames such as I-frames and P-frames. An I-frame is a complete image whereas
P-frames only contain the differences from previous frames.
The H.264 stream settings can be configured from the Video > Video Stream page. Select the H.264 tab. The settings defined in this
page will apply to all H.264 streams that do not use a stream profile.
The GOP length is the number of frames between two consecutive I-frames. Increasing the GOP length may save considerably on
bandwidth requirements in some cases, but may also have an adverse affect on image quality.
The Axis product supports the following H.264 profile(s):
• Baseline. The Baseline profile is recommended for clients that don't support CABAC entropy coding.
• Main. The Main profile provides higher compression with maintained video quality compared to the Baseline profile but
requires more processing power to decode.
• High. The High profile provides reduced bit rate and higher compression with maintained video quality compared to the
Main profile but requires more processing power to decode.
The bit rate can be set as Variable bit rate (VBR) or Maximum bit rate (MBR). VBR adjusts the bit rate according to the image
complexity, using up more bandwidth for increased activity in the image, and less for lower image activity. When the activity in
the scene increases, the bit rate would usually increase as well. If there is a surplus in bandwidth, this may not be an issue and
selecting Variable bit rate (VBR) will be sufficient. But if bandwidth is limited, it is recommended to control the bit rate by selecting
Maximum bit rate (MBR). When the activity in the scene increases, VBR adjusts the bit rate according to the complexity, using up
more bandwidth for increased activity in the scene, and less for lower scene activity. MBR allows you to set a target bit rate that
limits the bandwidth consumption.
The MBR target bit rate works like the ceiling of a tent. It limits the bit rate, while maintaining some flexibility. The bit rate
may bounce up and down within the set target but when it nears the set target value, the limitation kicks in. However, because
MBR will always prioritize a continuous video stream, it allows temporary overshoots from the target bit rate. Because setting a
target value prevents the bit rate from increasing, frame rate and image quality are affected negatively. To partly compensate for
this, select which variable shall be prioritized, frame rate or image quality. Not setting a priority means that frame rate and
image quality are equally affected.
The current bit rate can be set to appear as text overlay. Under Overlay Settings, select Include text and enter the modifier
#b in the field.
To apply the settings, click Save.
Axis' Zipstream Technology
Zipstream is a bit rate-reduction technology optimized for video surveillance. Zipstream reduces the average bit rate in the H.264
stream by removing unnecessary data and makes it possible to allow higher resolutions, reduce storage cost or to keep recordings for
a longer time. To reduce the bit rate, Zipstream reduces the number of bits in the areas of the image that are less interesting from a
video surveillance perspective, for example the background. Image details that are important for forensic video analysis, for example
faces and license plates, are preserved with enough number of bits.
These Zipstream strength options are available:
• Off. Zipstream disabled.
• Lowest Zipstream strength. Low bandwidth reduction. No visible quality degradation in most scenes
• Medium Zipstream strength. Medium bandwidth reduction. Limited visual quality degradation in not prioritized areas in
some scenes
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