The MultiSource unit is a fully featured video and audio codec system with extra capabilities (e.g. video brightness control) that make it more suitable for some applications. There is a data sheet that we send out to our customers. The MultiSource when combined with the companion MultiView unit provide TV quality performance.
The MultiSource has six analogue video input sockets which may be configured as:
This is particularly useful for applications where a large number of cameras are required. Examples would be in certain security applications or when arranging a transmission from a large seminar room. Please note that multiple video inputs which are being concurrently digitised must be gen-locked in order that the MultiSource maintains maximum frame rate. Note also that the audio and video inputs on the MultiSource system are all RCA/Phono connectors. We have a special VideoBOX Synchronizer product which permits to use standards video products.
The MultiSource unit is able to digitise a full frame rate interlaced video stream (compared with the former AVA-200 which can only handle digitisation of a single field). This can be necessary, especially for NTSC signals, if extremely high quality video reproduction is required.
The MultiSource provides a radical departure from conventional real-time video transmission systems. The MultiSource does not transmit the digital video in scanline format. Instead a frame is broken down into a set of tiles, each tile consisting of 8 x 8 pixels. Tiles are encoded on to the ATM network encapsulated in AAL5 frames for transmission to the ATM network. The number of tiles that are packed into a single AAL5 PDU is fully configurable. The selection of this value, the pack factor, is a trade-off between most computer end points wishing to receive large PDUs for efficient processing and the amount of data that is lost when a packet is corrupted. The set of digital video formats supported comprises:
The MultiSource has three stereo audio inputs all utilising standard 3.5mm stereo audio jacks. All channels are capable of supporting either 8 bit or 16 bit operation and a variety of sampling rates including both CD (44khz) and DAT (48Khz) frequencies. There is a single audio output that is used for local diagnostic loopback.
Please note that the MultiSource has a single audio encoder unit on board and as such it is only possible to digitise one input at a particulat time (it does not make sense to multiplex the audio hardware in the way it was possible with video). Of course it is possible to dynamically change input channels when sourcing a digital audio stream.
A variety of sampling modes are supported:
A variety of sampling rates are supported:
In addition to the above the user is able to remoteley control the gain and input level (microphone or line) of an input. The audio format also borrows the concept of a sample packing factor from the video format. This should be set high enough so that workstations and PCs do not receive a large number of small packets and low enough such that the AAL5 checksum requirement at the receiver does not introduce unacceptable delay.
In addition to the array of controls that the MultiSource provides for altering the characteristics of the source digital video stream the MultiSource provides some additional capabilities:
The MultiSource has to operate over a range of ATM transmission interface speeds. An on board cell shaper enables the MultiSource controller to tune the output of the device in order to meet stringent ATM UNI 3.0/3.1 Quality of Service traffic contracts. For example, the MultiSource traffic shaper for a SONET/SDH interface operates from 28Kbps to over 100 Mbps in order to satisfy a wide range of transmission requirements. In particular the system has been engineered so that very good quality results may be achieved over the WAN interface. Please note that the cell shaping function is not applied to the audio stream since this is already at constant bit rate (cells are sent as soon as they are full of audio samples).
Check our white-paper which explains the different technical features available for our products.
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