Audio Visual Design Guidelines

Define the Requirements

49 views November 19, 2019 November 19, 2019 aetm 0

Requirements Gathering

AV Over IP is suitable for consideration anywhere video signals need to get from a presentation source to a display device or system output. AV Over IP can be used to many varying degrees, and each have their place and suitability, depending on your institution technology requirements in the short and long-term.

Whether it’s getting a signal from A to B or completely replacing your existing AV transport approach, AV over IP can often be a cost effective solution that allows adherence and alignment with the standards already employed by the network and ICT teams. 

Below is a list of common scenarios where the use of AV over IP may be applicable over traditional video transport approaches:

  • AV signal routing and distribution solution must be scalable for future expansion, at a room, building or campus level
  • Encoding every presentation source input and decoding content at all display devices and system outputs, allowing a ‘virtual’ AV matrix, completely replacing traditional AV transport methods
  • Augmenting traditional video matrix/switching technologies to expand system functionality with other examples found in this list
  • Content can be duplicated from a single presentation source to any number of displays or system outputs
  • Route content to/from AV systems across multiple rooms, buildings or campuses
  • Refurbishing spaces with existing network cabling and difficult or cost prohibitive building works requirements for direct point-to-point cabling solution.
  • Enhance remote monitoring, support and management workflow capabilities by employing network-connected transport solutions with signal health feedback.
  • AV solutions are required to comply with enterprise network standards and separate AV cabling is not allowed or preferred to be avoided
  • Opportunities to reduce hardware footprint in rack space and cost in traditional, large video matrix deployments
  • Content from multiple presentation sources may be presented simultaneously to a single display (Picture-in-Picture) or for Video Wall image processing
  • Live-streaming to displays, or computer devices on campus via the local network
  • Computers may connect to USB devices via the network, including the read/write of USB storage devices via the network

 

Technical Requirements

The table below describes common technical requirements and the associated design responses when deploying AV over IP:

 

Technical Requirement Design Response
Current network architecture not suitable for AV over IP
The network may not be designed to transmit AV over IP data streams satisfactorily, or with the appropriate bandwidth for the desired application
  • Deploy a dedicated network switch with appropriate network features for the AV over IP system
  • Ensure cabling and patching infrastructure meets specifications for AV over IP solution
A point to point AV over IP solution is required

An AV Over IP solution may be leveraged to connect two endpoints together that are on disparate network segments, or physically distant locations.

  • Multicast addressing may not be required, depending on hardware selection
  • Unicast video traffic must be supported between encoder and decoder
  • Uplink bandwidth between source and receiver must still be considered
AV over IP network must be isolated from other subnets
ICT security policy may request AV over IP network traffic not negatively impact other network traffic.
  • Deploy a dedicated, air-gapped network switch for the AV over IP system
  • IGMP not required
  • Multicast address not usednot 
  • Unicast or broadcast messaging
AV over IP codecs connected to different subnets, but must be able to stream across subnets

ICT security policy may require different device types be placed on different subnets

  • Network traffic must be routed between subnets
  • IP address ranges or domain names must be specified for AV over IP codecs
Proprietary codecs must not be used
Users or institutional standards may require the  use of various software and/or hardware devices to encode or decode video streams
  • Avoid proprietary codecs
  • Encoders and decoders to support open standard codecs (e.g. H.264, H.265, or Motion JPEG 2000)
Low end-to-end latency

The input lag from presentation source to display must be as close to real-time as possible

  • Deploy lossless codec hardware/software with low latency as a primary specification
  • (maybe define some recommendations on latency thresholds ie. <40ms end to end etc?)
  • Codec must be “uncompressed” or “lossless”
  • Avoid  H.264, H.265 codecs as compression/decompression typically induces too much latency for the use of HID devices
Video must be highest possible quality

Video quality must not be compressed by the codec

  • Deploy a network switch with 10G Ethernet or SFP+ interfaces
  • Codecs must be “uncompressed”
Video must be high quality and network is 1Gbps

Video quality is high priority, but the network bandwidth throughput is limited to 1Gbps

  • Deploy a network switch with 1G Ethernet interfaces
  • Codecs must be “lossless”

 

Network IP Video Bandwidth Considerations

The first three columns of this table (Chapter XXX) provide the uncompressed video bandwidth of a signal, depending on resolution, refresh rate and colour depth. This information is provided to aid in understanding the various compression schema that are employed by AV over IP solutions.

 

‘Lossless’ Video Compression (Up to 1Gbps)

Consider the following when planning the deployment of codecs rated as lossless:

  • ‘Lossless’ products are often proprietary and encoder/decoder combinations must be of the same manufacturer and product range
  • Encoders and decoders based on the Motion JPEG 2000 video protocol fit within this category, however have the potential added benefit of interoperability between vendors . At present, due to vendor implementation of the standard and compression settings employed, encoders and decoders based on MJPEG2000 are often required to match manufacturer and product range, also. Check with manufacturers for interoperability between vendors and perform your own testing
  • Low end-to-end latency, often equal to or less than 50ms, suitable for lip-sync applications
  • Compression schema employed should be visually undetectable, producing a high image and audio quality.
  • Switch backplane, network topology, including uplink bandwidth capacity and rendezvous point location must be considered and discussed with network design/operations teams, as these solutions can place a significant amount of bandwidth on the data network, depending on network typology and configuration.
  • Always refer to  the vendor-specific white paper or design guide for a list of required protocols when considering the deployment of this option

 

‘Lossy’ Video Compression (Up to 25Mbps)

Consider the following when planning the deployment of codecs rated as lossy:

  • Lossy codecs typically use open standard codecs such as:
    • H.264
    • H.265
    • MJPEG2000 at high compression ratios
  • Highest end-to-end latency due to encoding process time + network transit time + decoding process time
  • Tolerance for image and audio quality degradation required. Testing for specific applications, using the required content source and test display is recommended 
  • May be suitable for deployment on networks with low bandwidth

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