5
Adaptive Rate Control (ARC)
ARC is a feature that adjusts the compression bit rate and
the frame rate of MPEG-4 data in order to meet changing
traffic conditions over a network. Round Trip Time (RTT)
and actual IP packet loss are both monitored to determine
traffic conditions, and the bit rate and frame rate are
adjusted automatically. “Drop Outs” (a breakup in
transmitted images) can be avoided when a system is
equipped with the ARC feature. The following is a
graphical representation of how ARC works:
Without an ARC feature, as the available network
bandwidth is reduced due to high-traffic conditions, "Drop
Outs" occur.
With ARC, as the available network bandwidth is reduced
due to high-traffic conditions, the MPEG-4 data bit rate is
reduced. This lowers image resolution slightly, but smooth
moving images are still transferred.
If network traffic conditions continue to increase, then the
ARC feature lowers the frame rate of the data so that
dropouts do not occur and a continuous image stream is
transferred. This method still provides smooth moving
images at a lower frame rate.
Network Technologies
Drop Out
0 fps
30 fps
30 fps
Without
ARC
GOV
Available Network Bandwidth
15 fps
30 fps
30 fps
With ARC
(frame rate
reduction)
Available Network Bandwidth
30 fps
30 fps
30 fps
With ARC
(bit rate
reduction)
Available Network Bandwidth
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