Authors: Jed Deame, CEO, Nextera Video; Antoine Hermans, CTO, Adeas; Rob Green, Senior Manager Pro AV & Broadcast, Xilinx
The Growing Need for AV over IP
There is an ever-present demand for better quality and connectivity in AV. As camera and display technologies improve, the images they capture and present get ever closer to “real-life” viewing. Pro AV is spearheading much of this demand, as use cases dictate interaction with displays from short distances, such as collaboration screens in meeting rooms, or the magnification of video images provided by large format displays in digital signage and LED walls. As video frame sizes and frame rates increase from HD to 4K and 8K and from 60fps to 120fps, connectivity bandwidth between video sources and displays needs to keep up. For example, uncompressed 4Kp60 video over HDMI 2.0 uses an aggregate bitrate of up to 18Gbps, severely limiting cable distances.
In the past, and depending on the protocol used, supporting higher resolutions and frame rates would require either the use of compression, multiple video links, or a new standard and cabling specification altogether. However, AV over IP is emerging as the preferred way to support higher bandwidths, extend the reach of point-to-point connections, reduce cost of infrastructure and enable a more flexible and agile way of using equipment on the network.
AV over IP Technologies
As with any emerging technology, early adopter suppliers often aim to standardize what is essentially a proprietary technique and the industry ends up with limitations and compromises. This can be very successful when the technology “just works”, and interoperability is less of a concern, but professional AV systems really need something scalable, something that works independently of resolution and network speed, and isn’t tied to a single vendor’s product. For example, compare offerings in table 1 and it’s clear that only SMPTE ST 2110 is truly scalable and vendor-independent:
Table 1 – Examples of AV over IP Technologies for Pro AV
SMPTE ST 2110
The SMPTE ST 2110 suite of standards was developed by the best and brightest minds in the industry, ensuring that it would be a flexible and scalable system for many years to come. As a result, there are many sub-standards as part of ST 2110. They include the following:
Table 2 – SMPTE ST 2110 Suite of Standards
These sub-standards may be mixed and matched to meet a particular application or use case. For instance, while TV broadcasters are content with uncompressed video, many Pro AV users prefer compressed video (ST 2110-22), enabling cost effective interfaces such as 1Gbps CAT5 cable. In addition, multiple links may be aggregated using RP 2110-23.
Another important component is timing and latency. Synchronization of network nodes is necessary to realize low-latency. ST 2110-10 specifies that nodes need to be synchronized according to the ST 2059 standard which consists of two sub-standards:
Table 3 – SMPTE 2059 Standards
They specify the use of the PTP standard (IEEE 1588v2) and the generation of alignment pulses from the PTP time to align the media (e.g. video frames). Synchronization over Ethernet is completely different from synchronization via Genlock, although the end result is similar. This is because Ethernet is packet-based, and the time it takes for a packet to reach its destination over the network is not fixed. The PTP protocol solves this issue. For best timing results, the use of PTP aware switches (transparent clocks, boundary clocks) should be used, but smaller systems don’t necessarily need them. PTP synchronization not only guarantees perfect lip-sync, but also enables ultra-low latency, perfectly synchronized video displays/walls for live events, digital signage, etc.
AV over IP Control and Management
The Networked Media Open Specifications (NMOS) were developed by the Advanced Media Workflow Association (AMWA) for use in IP-based infrastructures to provide a control and management layer in addition to the transport layer provided by SMPTE ST2110.
The goal is to provide a means for straightforward interoperability between products from a wide range of manufacturers, enabling end users and service providers to build systems using best-of-breed components from multiple manufacturers. Furthermore, the NMOS specifications are mandated by the European Broadcasters Union (EBU) as part of their “Minimum User Requirements to build and manage an IP-based Media Facility.” There are several NMOS specifications available from AMWA, but the three key components are IS-04, IS-05, and IS-08.
IS-04, Discovery and Registration
IS-04 enables ST 2110 devices to be discovered and registered on the network and their abilities published. The Registration and Discovery Server (RDS) is found automatically via MDNS or DNS-SD for true “Plug & Play,” a feature highly desired by the Pro AV community.
IS-05, Connection Management
IS-05 enables ST 2110 devices to be configured and switched in a standard way by any broadcast controller. An example of a broadcast controller is an HDMI Router-like button panel, or soft control panel via a simple HTTP API. With NMOS, the days of complex vendor-specific control programming are over!
IS-08, Audio Channel Mapping
IS-08 introduces Audio Channel Mapping, a key feature enabling audio channels to be re-mapped at the transmitter or receiver. The IS-08 API allows the routing of multiple diverse audio streams to any receiver.
A major goal for the next stages of standardization are to make interoperability and usability even easier. IS-09 is currently in development to define a system-level API, which provides media nodes on the network with access to global system parameters when they first boot so that they start working immediately after (re)connection. JT-NM TR1001.1 has a goal to enable easier connection and configuration with minimum user interaction. Other developments in NMOS are focused on security and include the use of HTTPS (encrypted control) and access controls to ensure the AV system is not compromised by unauthorized users.
ST 2110 was designed from the ground up for seamless interoperability across multiple vendors. This is key to accelerating the adoption rate. End users do not want to be locked into a single vendor and are embracing this interoperability.
In order to facilitate interoperability testing, the EBU and IRT in conjunction with the Joint Taskforce on Networked Media (JT-NM) have begun a testing program called “JT-NM Tested”. Vendors of ST 2110 products from around the world are regularly invited to a huge plug-fest. The JT-NM administers compatibility testing for both the electrical transport of packets and the NMOS control system. They publish the detailed reports on JT-NM.org. These reports provide confidence that purchased systems will be truly interoperable.
Case Study – KVM over IP for the Pro AV Market
Although USB over IP for keyboard & mouse extension is not explicitly defined in the ST 2110 suite of standards, PESA Switching Systems contracted with Nextera Video to develop a KVM system building upon the principals of ST 2110 and NMOS Control. The resulting system enables computers in multiple locations to be attached to an IP network and controlled by users anywhere the IP network reaches.
Figure 2 – KVM over IP with NMOS control
The system supports up to 4Kp60 video over commodity 1G copper ethernet links to enable cost-effective scaling. Visually lossless compression and ultra-low latency provides users with the experience of sitting directly in front of the remote PC.
Adaptable Platforms for AV over IP
With emerging technologies such as AV over IP and ST 2110, it’s important to be adaptable to changes. While there are devices specifically designed for IP-based implementations, many equipment designers prefer to adopt programmable platforms such as standalone FPGAs or, more frequently, SoCs combining FPGA fabric with embedded ARM processors. This provides an ideal link between software and AV domains as well as Ethernet/IP traffic, combining interfaces with video, audio and software processing functions in the same device. The programmable nature of these devices means they are adaptable to new and changing video formats and codecs, with scalability and complete flexibility to support multichannel AV and the software stacks to enable reliable network transport. In addition, FPGA core suppliers such as Nextera Video and Adeas provide complete solutions to enable fast time to market for manufacturers.
Although ST 2110 was initially developed for the television broadcast space, it fits comfortably into Pro AV across many applications, from uncompressed 10/25G for the high-end market to compressed 1G for the commodity market. It is resolution and network speed agnostic, and a common standard (NMOS) control interface enables cost effective controllers. Finally, ST 2110/NMOS interoperability enables the end customer to use multi-vendor solutions seamlessly.