AXIS 231D+/232D+ Network Dome Camera User's Manual

12 AXIS 231D+/232D+ - Video StreamsWhen using MPEG-4 it is also possible to control the bit rate, which in turn allows controlof bandwidth usage. CBR (constant bit rate) is used to achieve a specific bit rate by varyingthe quality of the MPEG-4 stream. When using VBR (variable bit rate), the quality of thevideo stream is kept as constant as possible, at the cost of a varying bit rate.How to stream MPEG-4Deciding the combination of protocols and methods to use depends on your viewingrequirements, and on the properties of your network. The available options in AMC are:Unicast RTPRTP over RTSPRTP over RTSP over HTTPThis unicast method (RTP over UDP) should be your firstconsideration for live unicast video, especially when itis important to always have an up-to-date videostream, even if some images are dropped.This unicast method (RTP tunneled over RTSP) is usefulas it is relatively simple to configure firewalls to allowRTSP traffic.This unicast method can be used to traverse firewalls.Firewalls are commonly configured to allow the HTTPprotocol, thus allowing RTP to be tunneled.Unicasting is used for video streaming,so that there is no video traffic on thenetwork until a client connects andrequests the stream.Note that there are a maximum of 20simultaneous unicast connections.Multicast RTPThis method (RTP over UDP) should be used for live multicast video. The video stream is alwaysup-to-date, even if some images are dropped.Multicasting provides the most efficient usage of bandwidth when there are large numbers of clientsviewing simultaneously. A multicast broadcast cannot however, pass a network router unlessthe router is configured to allow this. It is not possible to multicast over the Internet, for example.Note also that all multicast viewers count as one unicast viewer in the maximum total of 10simultaneous connections.AMC negotiates with the camera to determine the transport protocol to use in the orderlisted above. This order can be changed and the options disabled, to suit specificrequirements.