Axis Q1942-E Bedienungsanleitung Seite 18

AXIS Q1942-E Thermal Network Camera
Video and Audio
• Palette. The image can be colored by applying a palette. Colors in the image indicate temperature differences and can be
used to improve visibility of fine details. The palette selected here is used as the default palette, other palettes can be
selected on the Live View page.
• Maximum frame rate. To avoid bandwidth problems, the frame rate allowed to each viewer can be Limited to a fixed
amount. Alternatively, the frame rate can be set as Unlimited, which means the Axis product always delivers the highest
frame rate possible under the current conditions.
• 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 & Audio > 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):
The bit rate can be set as Variable bit rate (VBR) or Constant bit rate (CBR). 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
Constant bit rate (CBR). 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. CBR allows you to set a target bit rate that
limits the bandwidth consumption.
The CBR 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 CBR 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
• Highest Zipstream strength. High bandwidth reduction. Visible quality degradation in not prioritized areas in many scenes
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