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AVx VideoLink

Tracking, Fusion & Distribution

AVx VideoLink is a client-server software application that manages the distribution of network camera video across unreliable, or variable bandwidth, data links. In such situations, occasional loss of data packets from the video stream can have an exaggerated effect on the continuity of a video stream, with loss of picture quality within a frame and over time.

AVx VideoLink is an adaptive real-time encoding process that automatically adjusts the encoding parameters of the video distribution to adapt to varying network loads, latency, and loss of packets. It provides significantly improved image quality when the underlying network is unreliable through packet loss or variable bandwidth, as is often the case with wide area networks, for example.

Use of standard video compression technologies and network protocols is fine for local area networks, where the network is generally reliable and packet loss is low.  However, for wide-area networks, composed of several layers of varying reliability, packet loss may become a significant issue.  Reliable network protocols, such as TCP/IP, can provide a mechanism for guaranteeing packet delivery but the latency that they introduce makes them unsuitable to real-time systems.  A more intelligent solution is needed: AVx VideoLink.

AVx VideoLink is a solution to the problem of unreliable networks. It implements a special encoding scheme that uses feedback from the receiving client to guide the encoding process, allowing the encode quality to be adjusted dynamically, making best use of the available network capacity.  AVx VideoLink comprises two distinct parts:

  • a server process to manage receipt of camera video and onward network distribution
  • a relay process to monitor network performance and provide the client interface

The server and relay processes reside at either end of the unreliable link.  Display clients can connect to the AVx VideoLink relay application using standard RTSP or ONVIF protocols, providing an effectively transparent end-to-end link from camera to display.

AVx VideoLink can be used in conjunction with other Cambridge Pixel products. For example, the RadarWatch application provides a field-proven and operator-friendly combined display of radar and multiple camera video streams. The RDR data recording and replay application can record radar video and camera video together with other data streams. RDR can be deployed near the sensors, co-located with the AVx VideoLink server, to record ‘original quality’ camera video that can then be replayed, at the same time as live video, across a WAN or point-to-point link for display.

Network Protocols

Camera video encoded by standard compression methods such as H.264 can be distributed using protocols such as RTSP or ONVIF. For reliable local area networks, this approach works well and no special precautions are required. Using standard, connectionless network protocols such as UDP/IP, there is no guarantee that packets will be delivered in sequence, or even at all, but in practical network configurations with simple network topologies the reliability is sufficient to maintain a real-time data stream.

In wide area networks, for example those relying on low bandwidth data links, the packet loss arising from UDP distribution may become significant. Depending on which part of the compressed video stream is lost, the effect may be to lose a portion of an image or even a whole sequence of images, potentially lasting many hundreds of milliseconds. A connection-oriented protocol, such as TCP/IP, provides a mechanism for guaranteeing delivery of data by verifying receipt and resending when necessary. However, for real-time distribution, delayed delivery of network data will result in increased latencies in the display and the additional overhead of multiple retries will soon overload the network.

AVx VideoLink Encoding

The special AVx VideoLink encoding provides the perfect balance between low overhead/latency and high reliability. A limited number of retries are permitted to maintain the consistency of the data stream, but the encoder can also abort the retries if the latency becomes too large. This allows the encoding process to accommodate some packet loss with significantly improved resilience over normal UDP-based delivery methods.

A maximum per-channel bitrate can be specified, allowing only a portion of the available link bandwidth to be used so that other applications can share the link. If latency or packet loss worsen at any given time, the bitrate is automatically reduced from the configured maximum.

AVx VideoLink can use a combination of hardware-based and software-based H.264 encoding in the server application, allowing optimum use of the resources available. As well as encoding camera video at an adaptive rate to meet the preconfigured or real-time bitrate requirements, the server application can optionally modify the frame rate to meet the constraints of the link bandwidth.

  • Windows 10 compatible
  • Accepts RTSP or ONVIF camera video inputs
  • Re-encodes video for network distribution
  • Automatic adaption of encoding quality
  • Resilient video distribution
  • Channel priority support
  • Supports wide-area networks and point-to-point links
  • Client application recovers original RTSP or ONVIF data streams
  • Multi-channel, multi-client:
    • up to 8 cameras
    • up to 8 clients
Cambridge Pixel Sensor Acquisition and Tracking Product
AVx VideoLink Datasheet

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