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Sat 23 Jan 2010 04:00 AM

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Graphically speaking

The cost and complexity of designing HD and SD graphics simultaneously has been reduced significantly thanks to open platforms. Chyron's Phil Carmichael explains.

Graphically speaking
Graphically speaking
With more programmes being broadcast in HD and SD simultaneously, programmers have to create graphics content for both standards and here, the challenge is aspect ratio.

The cost and complexity of designing HD and SD graphics simultaneously has been reduced significantly thanks to open platforms. Chyron's Phil Carmichael explains.

There are many benefits to installing a good on-air graphics system, such as speed and ease of operation as well as the ability to read different industry graphics formats from other platforms. But the bottom line is that it's never been more important than now for broadcasters to produce the highest quality graphics for both channel branding and programme information purposes.

When a broadcaster is shopping around for an on-air graphics system, integration with current and future on-air graphics requirements is a must. This, together with the ability to expand storage, the price of storage expansion and ease of media management and backup management satisfies the majority of requirements.

With the advent of High Definition, it's no surprise that many broadcasters are looking to incorporate HD graphics capabilities. The cost and complexity gap between HD and SD graphics has been narrowed to the point that it is no longer difficult to obtain a cost-effective system to produce both HD and SD graphics. That has been true for a while with routers, distribution and cameras. It now applies to graphics as well.

The key to this performance jump has been the transition, industry wide, to software-based character generators and graphics running on high-performance open platforms.

The benefits of an open platform are clear.

First, there is no longer the need for expensive custom hardware that was typical of the last generation of graphics products. This speeds the time to market and lowers the cost to the end-user.

The other major benefit is that the open platforms are growing in performance at a tremendous rate. The next generation of GPU, CPU, storage technology or data bus have improved system performance at a rate much faster than the broadcast industry has experienced in the past.

Remote production trucks are being built with HD-ready infrastructure, and in many cases, that now includes the graphics equipment. Much of the graphics produced today for HD sports production, for example, is still upconverted from SD, because older-generation HD graphics equipment had severe performance limitations in terms of animation and speed compared to SD.

Most broadcasters agree that degrading the resolution by upconverting was less objectionable than degrading the look of the graphics by attempting to render in HD. With today's new generation of equipment, that is no longer a problem.

Some broadcasters may use a character generator plug-in to carry out offline work using a nonlinear editor; character and graphics generation is performed by the software plug-in. Many of the NLEs in the market now use open PC platforms, so they too have made a fast transition to HD, and there are many powerful and inexpensive systems available.Having said that, it is important that the plug-in is resolution-independent so that it can operate over a wide range of HD and SD resolutions, and that it can work with many open image file formats.

With an increasing number of channels on cable and satellite platforms, channel branding has become an ever-more-important component of broadcasting. It has evolved from a simple stationary logo in the lower right corner of the screen to sophisticated animations, sometimes with sound, running under complex automation control.

Quality and high resolution is also important, so upconversion is usually not an option. One advantage here, though, is that branding bugs are usually small, much less than full screen. This simplifies the design and lowers the networking storage requirements considerably.

HD files are large, particularly video clips, which are often used as animated backgrounds. Full-resolution, uncompressed RGBA is 250Mbit/s or 0.9 Tbytes/h. This amount of storage is not trivial, even with today's large drive capacities. In rough figures, it takes three times real time to transfer a clip over Gigabit Ethernet, and users are often finding it faster to "sneaker-net" a firewire drive from one machine to another rather than transferring the files via network.

Most programmers these days will find themselves broadcasting in HD and SD simultaneously, which means that they have to create graphics content for both standards; and therefore generally try to avoid having to create every graphic twice. The biggest problem here is not the resolution, since most graphics applications are resolution-independent and can scale an image up or down easily. The real problem, regardless of whether upconverting or working in native HD, is the difference in aspect ratio.

The most popular solution to this problem is to create all the graphics templates in 16:9 with a 4:3 protect. All important information, images and text are kept in a 4:3 area in the centre. Backgrounds, lower-third banners and other similar graphic elements can be extended to the end of the 16:9 area. When displaying in 4:3, the graphics system is programmed to crop the unused side panel area. This matches the technique most commonly used for camera shots that need to be used in both standards.

Keep in mind that generating animated computer graphics is a good stress test for an upconverter. If an upconverter allows for adjustments, be sure to take the time to optimise it for your graphics, as the settings are often significantly different from a general-purpose scene.

Look for spatial and temporal filter artifacts: Up- and down-conversion require digital filtering in order to interpolate the missing data. Spatial filtering causes ringing that is most noticeable around character edges and uniformity of colour problems, which you may see on the character face. Temporal filtering, or motion compensation, can sometimes cause severe artifacts on rolls and crawls, visible as filtering or hanging dots.

The ability to produce and transmit programmes is now available to all types of facilities. Armed with the correct information, a broadcaster of any genre can produce outstanding graphics for its viewers.

Phil Carmichael is director of Product Marketing at Chyron.

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