Transition Strategies: SDI to IP

Broadcasters, and production facilities that have significant investments in large-scale SDI plants are going to face technical and budgetary challenges as they transition to newer IP-based topologies. The need to support current SDI workflows during the transition will be key to a successful conversion. One solution is to use an ‘island’ approach, which can lower the transition risk when moving to the world of uncompressed IP video, audio, data and timing.

The push to transition from SDI to uncompressed IP audio and video has triggered the development of several approaches. Standards-based methodologies are beginning to emerge, such as SMPTE 2022-6, TR-03 (SMPTE 2110 draft) and TR-04. There are also a few other offerings, such as ASPENAIMS and NDI.

SMPTE 2022-6 is currently a prominent IP format for uncompressed audio and video.  It was one of the first formats to address carriage of uncompressed video over IP. 2022. Click to enlarge.

SMPTE 2022-6 is currently a prominent IP format for uncompressed audio and video. It was one of the first formats to address carriage of uncompressed video over IP. 2022. Click to enlarge.

As the details of these IP solutions emerge, engineers must now consider how to best manage their facilities in a completely new environment. However, operator workflows will most likely remain the same, at least in the short to medium term. The question becomes how to navigate this new IP technology and implement IP inside current SDI plants.

Current SDI topologies

It’s a given that engineers with large SDI core routers will not get rid of them quickly. This means these SDI devices will remain as part of most transition plans. Because facilities may have routers, perhaps 1056 X 2112 or larger, these systems are not only extremely large but also represent an enormous challenge in terms of what signals need to be selected for IP conversion.

The mainstays of today’s video operations are SD-SDI (270Mb/s), HD-SDI (1.5Gb/s) and 3G-SDI (progressive formats at 3Gb/s). When converted to uncompressed IP, these signals fit nicely into the 10Gb/s routing lanes of current IT infrastructure switch ports. However, higher resolutions of UHD-1 (12 Gb/sec) and UHD-2 (24 Gb/sec) are becoming common with OB trucks and it remains unclear as to how to approach these larger signal payloads.

Most baseband equipment is supplied with SDI I/O’s. Few vendors supply equipment with native uncompressed IP I/O’s. For example, cameras are just now starting to have IP I/O’s. Currently multiple and potentially incompatible IP implementations have been created because the broadcast market has been unclear about the type of IP to incorporate in broadcast equipment.

The creation of various uncompressed IP formats such as 2022-6, TR-03, AVB, and others has led to indecision about IP and therefore some manufacturers have avoided placing IP I/O’s in their equipment. Given that some production and broadcast equipment has IP while other gear does not, engineers will need to consider this as part of the transition plan.

IP topology choices

SMPTE 2022-5/6/7

SMPTE 2022-6 is currently the most predominant IP format for uncompressed audio and video. When introduced, it was also one of the first formats to address carriage of uncompressed video over IP. 2022-1 addressed the need to convert compressed ASI MPEG-2 transport streams to IP. As time proceeded, amendments to the SMPTE 2022 specification were adopted to include uncompressed SDI formats.

At the August 2016 Video Services Forum (VSF) interoperability tests, most of the 35 companies that participated in the 2022-6 testing were able to successfully send and receive the IP signals from 2022-6 IP transmitters to 2022-6 IP receivers. Given that 2022-5 allows for using FEC, 2022-5/6 will make the decision an easy choice for operators carrying signals across long haul networks that require FEC as well as containing all the essential elements of Audio, Video, and Ancillary Data, that are all bound together in one unicast or multicast IP address. WAN providers that haul signals from one city to another are particularly fond of this IP choice because it fits their current business model of providing point-to-point video delivery.

The 2022-5/6 signal construct also takes into account all of the synchronization components of the SDI signal because of the fact that it preserves the SDI blanking interval along with the ancillary VANC data. Because 2022-5/6 is very close to our current SDI formats, it seems logical to many developers and operators that it should be utilized for intra-facility use. In other words, when program signals need to be carried long distance much like ASI whose audio and video are unlikely to be manipulated, then the 2022-5/6 is a good IP solution.

SMPTE 2022-7 permits redundant/backup seamless switching. For those who feel they need extra signal protection and redundancy, 2022-7 allows for switching between two identical IP streams with no interruption of video or audio when the switch occurs. This is similar to the concept of switching two identical ASI streams, except that the switch it is done at the IP level.

TR-03 (aka SMPTE 2110 Draft)

In November, 2015, The VSF’s Studio Video over IP committee published Technical Recommendation 3 (TR-03). The main thrust of this document was the culmination of the broadcast industry’s input for creating a standard that was based solely on IP. Furthermore the committee found that 2022-5/6/7 didn’t address the true need to readily separate video, audio, and data streams, aka multi-level breakaway.

TR-03 video will utilize the internet standard RFC 4175, which eliminates the need for VBI, as well as other historical and additional signals. Click to enlarge.

TR-03 video will utilize the internet standard RFC 4175, which eliminates the need for VBI, as well as other historical and additional signals. Click to enlarge.

Therefore the VSF committee set itself the task of defining an IP format that could manage breakaway. This is done by treating video, audio and data as separate IP streams using separate multicast addresses.

TR-03 video will utilize the internet standard RFC 4175. It eliminates the need for VBI and other historical encapsulations and signals. This recommendation also incorporates AES 67 for the carriage of uncompressed audio signals and allows this IP audio signal stream to be transported separately thereby eliminating the need to ‘unbind’ the audio from the video as it is in the 2022 IP format.

Timing and synchronization may be one of the more important aspects to the TR-03 IP topology and the TR-03 document points to the use of SMPTE 2059-1/2. This standard is not explained easily. Its roots come from the IEEE 1588 standard using the Precision Time Protocol (PTP) that emits very precise time packets in the IP stream much the way that Network Time Protocol (NTP) works - only with greater precision. SMPTE 2059 allows video and audio signals to be ‘stamped’ with this precise time. This time stamping is not possible in SDI, so a transition to IP brings an unexpected benefit beyond genlock video timing. Such timestamping will help broadcast engineers address lip synchronization issues. 

SMPTE 2059-1/2 is rooted in the IEEE 1588 standard, which provides PTP. Click to enlarge.

SMPTE 2059-1/2 is rooted in the IEEE 1588 standard, which provides PTP. Click to enlarge.

The Alliance for IP Media Solutions (AIMS), an alliance of more than 50 members, that includes manufacturers, operators, and integrators, supports TR-03, which will soon become the SMPTE 2110 standard. The AIMS mission statement and roadmap is to implement the TR-03 standard in an effort to promote one open IP standard for using studio video and audio over IP among the AIMS equipment manufacturers.

VSF TR-04

This standard is a derivation of 2022-6 and AES67 using SMPTE 2059-1/2 as the timing mechanism. This may be of particular interest to operators who like the simplicity of 2022-6 but need to provide separate AES 67 audio.

Other approaches

The Evertz ASPEN system has recently been the choice of some operators who are anxious to incorporate the newer IP technologies. Here, the signal type relies on the MPEG-2 transport stream methodology. RDD 37 was recently enacted by SMPTE as a choice for those who like the idea of using IP in this manner. Parts of the RDD 37 standard will be incorporated within the new SMPTE 2110 standard in an effort to allow those operators who began with ASPEN to migrate to the SMPTE 2110 standard.

NewTek’s NDI is a proprietary IP video and audio method and it is being promoted as a choice for production applications, especially in editing.

Think islands

If the transition from analog to digital and from SD to HD is any indicator, it is likely that the transition to IP will be done in ‘islands’ rather than full facility-wide conversions. Even greenfield opportunities will likely be a mix of both SDI and IP equipment. So the question is this: Where in current broadcast facilities will uncompressed IP be first utilized and how will it be used?

One logical area for operators to try the technology may be video and audio monitoring using uncompressed IP. There are two considerations that support this idea: Monitoring is low-risk, and conversion to monitoring over IP can reduce the number of SDI output ports used on the current SDI core router. 

One benefit from trying an IP solution is that fewer router outputs are needed. Click to enlarge.

One benefit from trying an IP solution is that fewer router outputs are needed. Click to enlarge.

Another area that operators may consider converting would be smaller live production environments, such as backup control studios. In this scenario, staff would have the ability to get used to the newer IP environments while preserving existing SDI operation rooms.

In any scenario, it’s a good bet that SDI and uncompressed IP will coexist as a hybrid environment and allow operators to experiment with IP as a new signal type. As time goes by, operators will get used to using uncompressed IP signals, and they may find that there are some advantages in their workflows that favor IP over SDI.

Conclusion

There are many strategies an operator might utilize to migrate a baseband signal plant to IP, but if history is any guide, the transition will follow the familiar island approach that was used during the conversions from analog to digital and from SD to HD. It’s clear that the transition to IP will not be undertaken in wholesale fashion. Rather, SDI and IP will coexist for years to come simply because operators will not completely abandon prior investments. The scenario in existing facilities will most likely be some mix of old SDI and new IP in some combination that makes technical and economic sense for the broadcast facility.

It’s also important to note that during these transitions, workflows change. And one of the chief arguments supporting the move to IP is the ability to manipulate and control the signal more effectively than ever before. While there is much debate across the industry as to the advantages and disadvantages of IP carriage of audio and video, most industry experts concede that the transition from baseband SDI to baseband IP is inevitable.

Scott Barella, Chief Technical Officer, Utah Scientific

Scott Barella, Chief Technical Officer, Utah Scientific

Editor’s note: Mr Barella presented an expanded version of this article at the 2016 SMPTE Annual Technical Conference and Exhibition. Contact the organization to obtain a copy.

Comments:

good informative article

February 15th 2017 @ 19:50 by Michael Lynch
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