Long after the majority of TV viewers are watching in HD, most broadcasters will still be working in a hybrid SD/HD environment. For the foreseeable future, TV content will exist in many different forms, including vast archives of SD video material, film-based material with 2:2 or 2:3 cadences, graphics, captions and titles, animation with different frame rate sequences, and mixtures of all of the above.
Making all of this look good within the HD environment will be a challenge, and it's important for broadcasters to address this issue now, as purchases of HD displays move beyond the early adopter phase and begin to penetrate the wider market.
Thinking outside the box
When Snell & Wilcox developed the Quasar Ph.C HD upconverter, the company's objective was to improve performance by devising a system-level solution that could also handle embedded and AES audio and closed captions, and provide noise reduction, preprocessing, video enhancement, legalizer and clipper tools. The result is a system that provides clean and sharp high-resolution upconverted images from sources without introducing deinterlacing or conversion artifacts.
On the inside
Several different technologies make up the upconverter, with the most critical being a motion-compensated deinterlacer using Ph.C motion estimation technology.
Ph.C is a frequency domain technique, and as such, it is capable of zeroing in on details while ignoring factors, such as luminance levels and noise and grain, within the picture.
The estimating technology provides a correlation surface for the image, which communicates the motion and content on a pixel-by-pixel basis. So no matter what the motion speed or the content type, the correct processing is performed on each pixel. The result is a robust and reliable deinterlacing process.
Using this analysis, the upconverter can perform a fully motion-compensated deinterlace. If the input is 525 (480i) NTSC, the system converts this internally to 525 (480p), or twice the resolution of the original input. This deinterlaced image is then scaled to create the 720p or 1080i output. The meticulous deinterlacing process eliminates errors that would be magnified by scaling. By using a deinterlaced image for scaling, it allows users to sample points closer to the desired output pixel and thus maximize the resolution of the video output.
In addition to newly developed algorithms for upconversion and motion estimation, the upconverter combines several other technologies, including Prefix compression preprocessing technology, DEFT 2:3 cadence detection technology and CleanCuts, which prevents bleeding across cuts.
Additional functionality includes an enhancer, taken from the company's Archangel image restoration solution. The enhancer enables the system to handle low-resolution or poor-quality sources.
The system's gamut legalizer ensures that signals are legal and maintains the optimum look for the picture when transmitted, encoded and displayed. The upconverter's integrated color space converter addresses the differences between color space in SD and HD content. Built-in aspect ratio conversion handles typical conversions as well as user-configured conversions that can be controlled by wide-screen signals.
The Quasar Ph.C integrates easily into a variety of facilities and applications, providing broadcasters with a fast fix for delivery of HD content in a world where most sources are still SD. It is a valuable tool for future expansion of HD operations.
Ian Ellis is the product manager, conversion, for Snell & Wilcox.