DTV answer book: We've got answers!

Does IP networking have a role in today’s broadcast plant?

By Carsten Baumann

Ever since new network technologies have been introduced broadcasters have been investigating and exploring the possibilities for using them in their operations. Several years ago ATM appeared to be the future standard, not only for WAN connectivity, but also to be used for in-house distribution.

The traditional X-Y crosspoint switch seemed to become obsolete as it was envisioned that each device, such as VTRs, cameras, monitors and even microphones would have a built-in ATM network interface connector, and all equipment would be simply plugged into a large enough switch. A central network management system could have been used to control all signal flows and ensure smooth operation.

Well, today we realize that this was a good idea that hasn’t been realized, as it is simply cost prohibitive. Hence ATM, with the exception of a few installations in the audio domain, was never successfully implemented in the local broadcast environment. However, it has been well adopted in the WAN market.

Ethernet (IEEE 802.3) and packet switching have long been the underlying technology for computer networks and the Internet. They are starting now to be used for voice and video communications as new and improved network technologies, such as DiffServ, MPLS and VPNs, become widely available.

Utilizing these new technologies, the former unreliable and unpredictable nature of IP networks will now offer highest quality of service. These new services, in combination with highly developed IP gateway technology allow for the exchange of high-quality real-time and latency sensitive applications over IP networks as an alternative to existing distribution methods, such as satellite, leased lines and ATM. From a business perspective, IP networks are becoming economically more attractive to distribute high-quality video and audio content.

The integration of those SDI/IP gateways is as simple as the implementation of ATM gateways. Having used the word simple may create confusion, as it doesn’t appear to be simple. Current installations demonstrate that the classic broadcast engineer needs to develop an understanding of designing a network architecture — its limits and benefits, and its performance characteristics. At the same time, traditional network designers need to develop an understanding of the gigantic amount of data that broadcasters will routinely move through these networks. If we talk about SDI we are moving 270 Mbits/s in real time. Every bit needs to be delivered with minimal latency on time. No packets dropped, no packets repeated.

The real benefit is that IP networks offer the greatest flexibility and can be scaled dynamically. Systems can be designed starting from a small installation and can scale dynamically without introducing difficult complexity. With gigabit Ethernet there is currently sufficient bandwidth available to actually accommodate up to three SDI signals (3 x 270 Mbits/s = 810 Mbits/s) via a single switched IP network path.

IEEE 1394

IEEE 1394, also known as FireWire, was originally designed as an inexpensive consumer interface to connect cameras with computers for editing, and to replace the cumbersome SCSI interface for storage devices. It appears to be attractive for certain broadcast applications and has been adopted by a few manufactures. 1394 currently provides bandwidth of approximately 400 Mbits/s, but 1394b supports up to 800 Mbits/s, and future upgrades will allow up to 3.2 Gbits/s via fiber interconnects. In order to provide equivalent networking capabilities to Ethernet, FireWire switches have become available to companies relying on this technology to build larger networks. It is questionable if these networks are cost competitive to Ethernet, as the majority of network communication architectures are based upon Ethernet. Most likely IEEE 1394 will find its niche, but may be less widely adopted in broadcast applications.

As cost is one of the most critical factors determining whether a technology will be successful or not, Ethernet has the potential to become the most dominant network architecture within the broadcast community. I believe that in the not too far future we will see a wide range of applications running on Ethernet vs. traditional X-Y crosspoint switches.

Carsten Baumann is director of product management for Leitch.

By Stan Moote

In today’s broadcast facilities, Ethernet is typically been used to control and monitor various vendors’ equipment. Having a simple and low-cost common physical and data link layer allows for easy integration, and flexible and dynamic scalability. As Ethernet is the backbone of the Internet it allows for global access. This can make broadcast engineers’ job easier as it requires almost no local presence. Remote diagnostic, control and monitoring are the key installations using Ethernet.

Using IP over Ethernet for real-time long-haul data distribution is becoming attractive as well. IP over Ethernet provides an alternative to existing distribution methods, such as satellite, leased lines and ATM. Thus connecting geographically distributed local broadcast stations using Ethernet becomes a key method for centralcasting.

Furthermore, scalability and dynamic bandwidth allocation make IP over Ethernet a powerful tool in today’s fast-changing broadcast environment. Ethernet already provides the sole dominant network architecture when video and audio servers exchange information using the File Transfer Protocol (FTP). This non-real-time application is already used in WAN, MAN and LANs. Security issues arise, but can be solved by using encryption or conditional access methods.

For in-house, real-time critical data distribution over Ethernet, from a commercial perspective Ethernet seems to be a little bit far out. In order to use Ethernet to distribute SDI signals, it first of all needs to provide the bandwidth. Gigabit Ethernet will accommodate this bandwidth requirement as even multiple 270 Mbits/s SDI signals fit nicely into gigabit Ethernet. It also needs to provide reliable QoS. Already today, we can see that these QoS mechanisms are coming into maturity.

But the distribution of SDI signals over IP networks inside the broadcast facilities still seems to be cost prohibitive. Considering that most traditional broadcast products don’t provide Ethernet NICs, an external video and audio-to-Gigabit Ethernet gateway is required. In recent studies we found that the cost of gigabit Ethernet Layer 2 switches will be approximately 20 percent of the solution cost. The remaining 80 percent accounts for the actual IP gateways.

Currently the break-even point is somewhere around a 128x128 matrix, considering one layer of SDI, a dual layer for stereo audio and half a layer of control. But we can see that more and more equipment vendors are implementing Ethernet NICs in their equipment for signal connectivity. Have a look at this year’s NAB and you will be surprised how fast Ethernet is being adopted. Providing these Ethernet NICs inside the equipment will allow for a more cost-effective solution, and the idea of using a switched packet network approach to the design of broadcast facilities will become more feasible. In my opinion we are currently at the same stage as when SDI was introduced several years ago. At the beginning only a few equipment vendors provided SDI I/O ports and external conversion equipment was required to take advantage of the digital signal enhancements. Nowadays most equipment provides SDI I/Os. I believe it is fair to assume that this will happen with Ethernet and with gigabit Ethernet as well.

Stan Moote is chief technology officer for Leitch.

What are the benefits of 24p, and for what applications should it be considered?

By Michael Brinkman

The two factors driving the spread of 24 fps video acquisition into areas traditionally reserved for film origination are the same ones that first brought 24p to theatrical production: cost savings and convenience. In the hands of skilled practitioners, film remains a truly magnificent medium for capturing images. But the realities of today’s less-time/less-money production world make it increasingly difficult to find budget for the high costs of film stock, processing, printing and telecine sessions needed to move pictures captured on film into the broadcast world. For a growing list of producers, the image quality of high-definition video coupled with the immediacy and convenience of videotape makes a compelling argument for switching to electronic origination. As an example, the producers of a 22-episode television series, which is entering its second season, recently reported that switching to HD will save them $750,000 in production costs this year.

Of course, the basic arguments about cost savings and convenience apply to HD in general and not specifically to the 24 fps versions of HD that most closely mimic film. Unless you have been living in a cave for the past couple of years, you know the debate over frame rate(s) has reached a near religious fervor, with some declaring that even 60 “frames” per second is “too slow,” while others hold to the belief that something magical resides in the 24fps cadence, which enhances storytelling.

The first, and most obvious reason to acquire video at 24 fps is to facilitate distribution of the final product on film. After all, a one-to-one relationship of video frames to film frames greatly simplifies much of the post-production process. The lower the budget for any given project, the greater the impact of the up-front savings over shooting film. Those dollars formerly dedicated to film stock, processing and printing charges can be redirected in ways that may substantially improve the final product. And, because videotape is reasonably inexpensive and reusable, the director and actors may now have the luxury of shooting multiple takes or employing creative techniques like improvisation that simply can’t be done when burning budget-limited film stock. There is little question that shooting 24 fps HD can have a very positive impact on a lower budget feature.

The choice of frame rate is not always so obvious if the final distribution will be via a broadcast television signal. 24 fps video is a good choice if the project calls for shooting both film and video, particularly if 24 fps film makes up a sizeable portion of the overall footage. And, an argument can be made that 24 fps origination and mastering makes it easier for many post facilities to perform a conversion to 25 fps, 625-line (PAL) if overseas distribution is anticipated. Thus, 24 fps HD is becoming an alternative to shooting film for some episodic programs, particularly dramas that are most likely to see foreign distribution.

But what about more transitory, general-purpose programming that will not be syndicated or high motion/action programming like sports? In the case of the later, 60 fps HD is a far better choice than 24 fps. With 2.5 times more frames per second, 60 fps brings a certain fluidity and grace to moving objects that few have experienced before. (This applies equally to either a moving object in front of the camera or the camera itself if it is moving.) Sure, several notable examples — like ShowScan — exist of shooting 60 fps film and playing back at 60 fps, but the cost of such production remains prohibitive in all but the most specialized applications. We should also remember that 30 fps high-definition (1080i/60 format) remains the most affordable way to shoot and post HD. If production budgets remain depressed, there is a real possibility that 30 fps HD will be rediscovered as an affordable compromise between the drama-enhancing “look” of 24 fps and the motion-handling elegance of 60 fps.

So, while there is no doubt that the use of 24 fps HD will continue to expand as the tools become easier to use, there is equal reason to believe that creative cinematographers will discover the advantages offered by affordable, higher frame rates. Look for developments in both directions.

Michael Brinkman is vice president of strategic relations for Panasonic.