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AXIS Q6128-E PTZ Network Camera
Video
About 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 bitrates.
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.
About GOP length
A Group of Pictures (GOP) contains one I-frame followed by a number of P-frames. The GOP length is the number of frames
between two I-frames.
Equal values for GOP length and frame rate result in one GOP per second. A higher GOP length value results in more small-sized
P-frames and less big-sized I-frames while keeping the same frame rate. In other words, a high GOP-length value saves bandwidth,
but the video quality may decrease. A low GOP-length value increases the video quality but requires more bandwidth.
About H.264 profiles
The Axis product supports the following H.264 profile(s):
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Baseline: Use the Baseline profile if the client does not support CABAC entropy coding.
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Main: The Main profile uses CABAC and provides a better compression with maintained video quality. It requires a larger
amount of processing power to decode than the Baseline profile.
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High: The High profile provides a higher compression than both Main and Baseline profiles, but requires more processing
power to decode. High profile supports 8x8 blocks, which reduces the bitrate further compared to the Main profile.
About bitrate control
Bitrate control is useful to make sure the video streaming does not take up too much bandwidth.
About variable bitrate
Variable bitrate (VBR) adjusts the bitrate according to the image complexity. When the activity in the scene increases, VBR adjusts
the bitrate according to the complexity, using up more bandwidth for increased activity in the scene, and less for lower scene activity.
Variable bitrate is suitable if there is a surplus in bandwidth, where the increased bitrate may not be an issue.
About maximum bitrate
If you have limited bandwidth, we recommend Maximum bit rate (MBR). MBR allows you to set a target bitrate to control the
bandwidth consumption. The target value limits the bitrate, but it maintains a flexibility to be able to prioritize a continuous video
stream. Consequently, the frame rate might need to go down and the image quality might decrease. To partly compensate for this,
you can select which variable shall be prioritized. Not setting a priority means that frame rate and image quality are equally affected.
How to set an H.264 profile
1. To change the settings for all H.264 streams that do not use a stream profile, go to Video > Video Stream > H.264.
2. To increase or decrease the number of frames per GOP, set the GOP length.
3. Select one of the H.264 profiles.
4. Select one of the following:
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Variable bit rate
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Maximum bit rate
5. If you select Maximum bit rate, select which variable to prioritize in the Priority drop-down list.
6. Click Save.
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