Axis 214 PTZ User Manual

Also see for AXIS 214 PTZ: Specifications Product guide Operating instructions Installation guide Specifications

Contents

16 AXIS 214 PTZ - Video and Audio StreamsAudio Stream TypesThe audio stream types for audio are:• G.711 - International standard for encoding wired-telephone audio. Uses PCM samplesto compress audio where higher signal values are compressed more than lower values.In Axis products, this sets the coding type to μ-law 64 kbit/s.• G.726 - Uses PCM samples to code the difference between samples (ADPCM). Reducesbandwidth without losing too much useful audio. In Axis products, this sets the codedbit rate to 24 or 32 kbit/s.All stream types are ITU-T standards and operate on frequencies of up to 4 kHz.MPEG-4 protocols and communication methodsTo deliver live streaming video over IP networks, various combinations of transportprotocols and broadcast methods are employed.• RTP (Realtime Transport Protocol) is a protocol that allows programs to manage thereal-time transmission of multimedia data, via unicast or multicast.• RTSP (Real Time Streaming Protocol) serves as a control protocol, to negotiate whichtransport protocol to use for the stream. RTSP is thus used by a viewing client to start aunicast session, see below.• UDP (User Datagram Protocol) is a communications protocol that offers limited servicefor exchanging data in a network that uses the Internet Protocol (IP). UDP is an alterna-tive to the Transmission Control Protocol (TCP). The advantage of UDP is that it is notrequired to deliver all data and may drop network packets when there is e.g. networkcongestion. This is suitable for live video, as there is no point in re-transmitting oldinformation that will not be displayed anyway.• Unicasting is communication between a single sender and a single receiver over a net-work. This means that the video stream goes independently to each user, and each usergets their own stream. A benefit of unicasting is that if one stream fails, it only affectsone user.• Multicast is bandwidth-conserving technology that reduces bandwidth usage by simul-taneously delivering a single stream of information to multiple network users. Thistechnology is used primarily on delimited networks (intranets), as each user needs anuninterrupted data flow and should not rely on network routers.