Axis P1357-E User Manual page 20

AXIS P1357-E Network Camera
Video and Audio
• Resolution. Select the default resolution.
• Compression. The compression level affects the image quality, bandwidth and file size of saved images; the lower the
compression, the higher the image quality with higher bandwidth requirements and larger file sizes.
• Mirror image. If required, the image can be mirrored.
• Rotate image. If required, the image can be rotated.
• 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 25.
Click Save to apply the new settings.
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):
• Baseline: Use the Baseline profile if the client does not support CABAC entropy coding.
• 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.
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.
20