Part 1: Background and key benefits of SMPTE ST 2022-6 on AWS Elemental Live

This two-part blog is a look at the Society of Motion Picture and Television Engineers (SMPTE) ST 2022-6 standard. This first post explores some of the reasons customers are transitioning from Serial Digital Interface (SDI) infrastructure to IP. It also looks at the trade-offs to consider when making the switch, and best practices using AWS Elemental Live with SMPTE ST 2022-6 & SMPTE ST 2022-7.

Part 1: Background and key benefits of SMPTE ST 2022-6 on AWS Elemental Live (this post) 
Part 2: Working with SMPTE ST 2022-6 on AWS Elemental Live Appliances 

Background

In order to meet requirements for interoperability, latency, quality, and reliability, broadcast workflows transport uncompressed video between and among workflow components. The start of digital signaling for video and audio in the late 1980s led to the wide adoption of Serial Digital Interface (SDI) as the interconnect standard. SDI provides almost unlimited interoperability for video workflow components in addition to deployment flexibility. However, as a purpose-built standard, it can be costly to implement and requires specialized equipment and knowledge to support. Those disadvantages were outweighed by SDI’s performance, reliability, and compatibility. Until recently, there was simply no alternative available that met broadcasters’ workflow needs for intra-facility video transport. No other network technology provided the performance and interoperability required. (For example, when 270 Mbps SD SDI was standardized in 1989, office networks, if they existed at all, were based on at most 10 Mbps “10-base-2” daisy-chained coaxial cable.)

As Internet Protocol (IP) networking performance improved, along with advances in signal routing, it became clear that — at least in theory — high-performance IP-based networks could be deployed to support transport of uncompressed video in broadcast workflows. Early attempts at this were clever proofs-of-concept but could not offer the reliability, performance, and flexibility that broadcasters demanded. So, SDI remained the norm.

Efforts to find a way to leverage IP networking in a standardized, interoperable way resulted in two standards for carriage of uncompressed video/audio over IP. Both of these standards met the above-mentioned requirements for broadcasters. This paper is the first in a series describing one of these, Society of Motion Picture and Television Engineers (SMPTE) standard ST 2022-6. (The other, SMPTE standard ST 2110, is covered in a separate series of blog posts.)

Simply put, SMPTE ST 2022-6 defines a mechanism for encapsulating the data (component video, uncompressed audio, and ancillary information such as subtitles and timecode) currently carried in SDI, and transports it reliably and with low latency over a local IP network. Significantly, that network can be provisioned with standard cabling and switching gear, and doesn’t require specialized components other than those needed to handle network traffic at the speeds required for real-time transport of video. It is no longer necessary to use special 75-ohm coaxial cable, BNC connectors, and unidirectional point-to-point connections.

Diagram showing the parts of an SDI signal and it being packetized into 2022-6 

Now that we have defined SMPTE ST 2022-6, what does it do for broadcasters?

Key benefits

SMPTE ST 2022-6 was built for real-time transport of uncompressed video, audio, and data over IP networks. Its main applications are for primary distribution and contribution workloads. In simple terms, video products that support SMPTE ST 2022-6 can use off-the-shelf IT networking hardware to deliver uncompressed video over a network. This removes the need for expensive SDI infrastructure that doesn’t scale easily.

The benefits of employing an uncompressed video over IP standard, such as SMPTE ST 2022-6, can be summarized as: scalability, flexibility, and agility.

Scalability

The conversion of SDI signals into SMPTE ST 2022-6 encapsulated IP packets can be achieved at a relatively low cost with off-the-shelf networking hardware. The scaling limitations that hamper SDI solutions can be bypassed by moving to an IP-based video network. This allows broadcasters to scale the size of their production workflows by adding or removing network hardware, typically using a Spine-leaf network architecture.

Interoperability gains can be realized after upgrading a network. SDI devices do not need to know about SMPTE ST 2022-6, employing an encapsulator or de-encapsulator bridges SDI to IP workflows. Legacy devices can remain in place, with core devices upgraded as needed (or as the budget allows). Pre-existing Tricaster-like devices (video switcher or compositor) or caption encoder may still live in an SDI world. These devices would push SDI out to an IP encapsulator, then an encoder that supports SMPTE ST 2022-6 can consume the stream generated by that encapsulator.

Delivering video over IP can also impact the number of channels a hardware video encoder can support. If the encoder employs SDI inputs to ingest video, its channel count is likely limited to the number of SDI ports on that encoder. If the encoder supports SMPTE ST 2022-6 inputs, its channel count is not limited by the number of physical inputs. Its channel count limits are instead defined by the network bandwidth and the compute resource the encoder supports.

While these points highlight the scalability of video over IP networks, planning is still needed when building or expanding an IP video network. For example, if an IP video network uses 10G interfaces, it can support 3G-SDI workflows. However, if future workloads need to support 12G-SDI workflows the network needs 25G interfaces to support the extra bandwidth. A single 10G network interface cannot support a packetized 12G-SDI signal. Although video over IP networks deliver scalability benefits, it is not “one size fits all.” Each component of the IP video network needs to be considered for current and future workloads.

Flexibility

Adopting an uncompressed video over IP standard such as SMPTE ST 2022-6 adds flexibility to video workloads. This is because IP delivery is agnostic. Adopting a new standard in an IP-based video network may reduce the need to re-architect existing infrastructure. Adoption could be achieved with a software update on existing video or network hardware, so no physical infrastructure changes are required. Once uncompressed video is packetized for IP delivery it does not matter if the format is SD, HD, or UHD. The consideration of adopting new IP standards is only tempered by the amount of network bandwidth the video and network hardware can support.

Doubling down on flexibility, packetized data delivered over an IP network is bidirectional. This means the Ethernet cable delivering the source video to an encoder can also be used to deliver the processed video streams from the encoder to their destinations. This is in contrast to SDI infrastructure, which is unidirectional.

Agility

Choosing an uncompressed video over IP standard such as SMPTE ST 2022-6 increases a broadcaster’s agility to test new ideas and workflows.  This can usually happen without building additional infrastructure. The format agnostic advantages that IP brings enables service providers to deliver new formats that become available in the future. This agility can be a differentiator, allowing service providers to quickly take advantage of new opportunities as they arise.

An uncompressed video over IP network also opens up the opportunity to test with other standards such as SMPTE ST 2110. For example, the AWS Elemental Live L800 series of encoders, fitted with a 25 GbE NIC support SMPTE ST 2022-6 as an input format. These encoders also support SMPTE ST 2110 as inputs and outputs. The ability to switch between SMPTE ST 2022-6 and SMPTE ST 2110 workflows adds flexibility and agility to facilities that need to process uncompressed video in real time.

SMPTE ST 2022 breakdown

The SMPTE ST 2022 standard is broken down into a series of eight documents; each tackles one specific part of the standard. The complete standard describes how to send digital video over an IP network. This includes documents for delivery of compressed video (MPEG2) over IP; Forward Error Correction (FEC) for real time video over IP; the transport of High Bitrate Media Signals over IP (this blog post’s area of focus); and seamless protection switching of IP datagrams (SMPTE ST 2022-7).

Each document describes operational requirements specific to each individual topic. For instance, the SMPTE ST 2022-6 document stipulates that a system supporting this standard must always have enough bandwidth available on the network to meet or exceed the IP streams network bandwidth that is generated. It also highlights that network paths should be designed with adequate bandwidth and a low enough error rate for end equipment to successfully decode streams. The document also confirms that support of RCF 4566, the Session Description Protocol (SDP) is not required for equipment supporting SMPTE ST 2022-6.

For reference the SMPTE ST 2022 standard suite comprises of:
ST 2022-1:2007 – Forward Error Correction for Real-Time Video/Audio Transport Over IP Networks
ST 2022-2:2007 – Unidirectional Transport of Constant Bit Rate MPEG-2 Transport Streams on IP Networks
ST 2022-3:2010 – Unidirectional Transport of Variable Bit Rate MPEG-2 Transport Streams on IP Networks
ST 2022-4:2011 – Unidirectional Transport of Non-Piecewise Constant Variable Bit Rate MPEG-2 Streams on IP Networks
ST 2022-5:2013 – Forward Error Correction for Transport of High Bit Rate Media Signals over IP Networks (HBRMT)
ST 2022-6:2012 – Transport of High Bit Rate Media Signals over IP Networks (HBRMT)
ST 2022-7:2013 – Seamless Protection Switching of SMPTE ST 2022 IP Datagrams
ST 2022-8:2019 – SMPTE Standard – Professional Media Over Managed IP Networks: Timing of ST 2022-6 Streams in ST

Transitioning to IP with SMPTE ST 2022-6

Transitioning to a video over IP network is relatively inexpensive and uncomplicated due to the availability of off-the-shelf IT hardware. However, consideration must be taken with the network bandwidth limitations of new hardware used to build or expand the video network.

The transition to IP can happen incrementally, enabling both SDI and IP workflows to run at the same time. This reinforces SMPTE ST 2022-6 standing as the ‘on-ramp’ standard for broadcasters to adopt IP workflows. The complete SDI signal is packetized, with the video, audio and data synchronized, removing the need for the Precision Time Protocol (PTP). This is unlike SMPTE ST 2110, where PTP is a requirement, and the video, audio, and data components are separated into individual essences. Separating the components provides greater flexibility at the cost of a little more complexity. SMPTE ST 2110 is ideal for production or live sports production environments where individual essences may need to be processed separately. In contrast, SMPTE ST 2022-6 is a perfect fit for contribution and distribution workflows. More information about SMPTE ST 2110 can be found in this post, which discusses using SMPTE ST 2110 with AWS Elemental Live.

As mentioned earlier SMPTE ST 2022-6 can take advantage of Forward Error Correction under SMPTE ST 2022-5, and Seamless Protection Switching under SMPTE ST 2022-7. SMPTE ST 2022-7 defines the delivery of two streams of identical content over potentially diverse network paths. This enables the receiver to select packets from either of the two identical streams, protecting against dropped packets over the network. SMPTE ST 2022-7 can also help mitigate the loss of an entire diverse network path. When considering the transition to IP, it’s important to note the benefits of SMPTE ST 2022-7. However, consideration is needed on the potential impacts this has on the design and cost of the network.

The AWS Media Blog has recently published an article that details the process of designing resilient ground and cloud networks with SMPTE ST 2022-7.

Another point to consider when transitioning from SDI to IP is security. SDI is inherently secure, but the same can’t be said for IP networks. Care needs to be taken when architecting IP networks that carry video. This is particularly important on devices like encoders that may need to publish their encoded video streams over the Internet. Firewalls should always be deployed; AWS Elemental Live encoders should have the latest software installed and they should never be publicly accessible.

Summary

SMPTE ST 2022-6 is the packetization of the entire SDI signal, enabling uncompressed video over IP. It’s most suited to contribution and distribution workflows and is the ‘on-ramp’ standard for broadcasters adopting video over IP. SMPTE ST 2022-6 facilitates the modernization of video over IP networks, while allowing both SDI and IP workflows to work side by side. SMPTE ST 2022-6 brings the scalability, flexibility, and agility of IP networks to uncompressed video workflows.