SCREEN AFRICA EXCLUSIVE:
Written by Mike Allan, Chief Technology Officer at Exterity
The AV industry is moving away from legacy analogue technologies and towards a future where IP networks dominate the delivery of video, audio and digital signage.
Yet IP-based AV technologies are not all the same and the terms ‘IPTV’ and ‘AV over IP’ (AVoIP) have increasingly been used in an interchangeable way and that has led to some confusion in the marketplace at a technical and application level.
The last decade has seen the rise of IPTV to replace older analogue technologies based on RF and less flexible matrix switches. The biggest benefits include the simplicity and flexibility of using a single shared structured cable network and relatively low-cost IP switches for internet connectivity, application data and AV. As, per port, Ethernet switching costs have declined while speeds have increased, today more than 95% of video and digital signage installations use some version of IPTV.
IP-based video solutions, including IPTV and AVoIP, work in a very similar way. Initially, content is ingested from a source. This could be a pre-compressed source such as broadcast TV, satellite, cable or DTV, or a Video on Demand server. Alternatively, this ingested content may be a baseband video source such as HDMI or SDI that is then compressed to reduce the amount of bandwidth.
This digital compressed video content is then turned into packets that are transmitted across an IP network in chunks. This transmission is normally multicast (one-to-many) or unicast (one-to-one), with packets flowing across the IP network through switches and along ethernet cables or Wi-Fi networks to reach a destination. At the destination device, the packets are received, assembled back into video, decompressed and displayed on a device such as a TV screen, video wall, projector or even smartphone.
Each of these steps adds a time delay, or latency, between transmission from the source to being displayed at the destination. In addition, each time the source video is compressed and decompressed, there is a degradation in visual quality, which is a trade-off for the video content being mathematically altered to use less bandwidth. Although a very simplistic description, this concept is broadly the same for IPTV, AVoIP, Software Defined Video Over Ethernet (SDVoE) and several other specialist IP-based AV technologies. The major differences between the technologies is the degree of compression, the resulting latency and the network needed to carry the content.
Benefits and Compromises
In very simplistic terms, IPTV uses the most compression and introduces the greatest latency while using the most common type of networks. SDVoE has the least compression and latency while requiring the most performant network – with AVoIP balanced somewhere between the two. However, for most HD/4K content for hotel infotainment, conference centres, stadiums and corporate offices, the visual difference and latency trade-off are imperceptible to most end user scenarios.
The primary strength of IPTV technology is its maturity and flexibility, which has led to a high level of adoption within the market and the widest ecosystem of technologies supporting IPTV, including set-top boxes and Smart TVs, as well as tablets and smartphones, which can all display IPTV streams via a wide array of apps.
AVoIP, including SDVoE at the top end, has emerged predominately as a technology that serves use cases that require higher visual quality and lower latency. Although AVoIP is functionally like IPTV, its ability to deliver lightly-compressed video at the typical 1GB Ethernet network level is its most compelling advantage.
However, for any endpoint with a consumer-grade 55” LED display, this advantage does not translate into a tangible visual benefit for the end viewer when looking at content such as TV, movies, sport or digital signage, as the screen is not big enough to reflect the improvement in quality through less aggressive compression. However, where detail such as smaller text or precision diagrams is important, the higher visual quality can be of benefit. That means that AVoIP is most beneficial – even necessary – for use cases such as medical procedures using cameras or where video is being displayed on very large 3×3 or 9×9 video walls and native 8K video, where compression artefacts are more noticeable.
The Need for a Network Upgrade
The biggest compromise inherent in AVoIP, and more so with SDVoE, is the requirement for a more advanced network to deliver uncompressed video. This means that customers who need to carry multiple streams must invest significantly in a move to 10GB ethernet network and potentially upgrade not just switches, but structured cabling across an entire facility.
At present, many of the AVoIP solutions are still relatively immature, which makes the number of suppliers and alternatives rather limited. This means a higher cost price for solution elements and almost certainly an expensive network upgrade. For most system integrators, choosing which IP technology to use will depend on the application and – as always – it’s a case of horses for courses.