The evolution of TV video quality and the rapid rise in video bandwidth requirements over the past few years has been nothing short of remarkable. While 480i analog systems required only a 6 MHz bandwidth, today's 1080p-compliant systems deliver a 1920H x 1080V image, which requires data delivered at 148.5 MegaPixels/second (MPPS). This has contributed to much more realistic images; progressive scanning (as opposed to interlaced) doubles the data rate, but results in much smoother motion with far fewer artifacts.
A similar evolution has occurred in color depth. Most currently available HDTVs offer 8-bit color (meaning 219 levels of brightness for each of the three colors making up a picture element, or pixel). Emerging new "deep color" standards for video increase this resolution to 3504 levels per color (using 12-bit color). Moving to a new color space, called xvYCC, raises this to a full 4096 levels per color and delivers the most realistic images consumers have ever seen. Of course, this also increases the amount of data that needs to be moved around the home by a factor of more than 18. The problem ATV designers must address is how to deliver these vivid high quality images at a price point the average consumer can afford.
To manage this explosion in data rates, the ATV industry has turned to video compression technology. While there is a growing variety of video compression COder DECoders (CODECs) available, they are generally based on the Discrete Cosine Transform (DCT) with inter-frame motion estimation to achieve very high levels of compression. These CODECs (such as MPEG-2, MPEG-4, H.264, AVC, and others) are very efficient, but they are extremely computation-intensive on the compression side. Efficiency comes at a cost. This cost is entirely appropriate for the distribution of television programming and films over the air, satellite, cable, or DVDs, where the available bandwidth is severely constrained and the application is "compress once, decompress many."
In the home entertainment system of the future, however, a different environment exists. With modern RF, coaxial, network, and powerline transports, far more bandwidth is available; signals exceeding 100 Mbps are commonly distributed. At the same time, there are numerous applications were it is necessary to compress an HD source in the home, in real time, at low cost. DCT-based inter-frame compression is ill-suited to this task.
Analog Devices has been a pioneer in an entirely new class of compression algorithms based on wavelet mathematics. ADI started work in 1993; this approach was standardized by the JPEG committee at the end of the decade and named JPEG2000. Now internationally recognized, JPEG2000 technology applies two-dimensional filtering and sub-sampling in hierarchical and multi-step combinations. This offers a number of advantages, including scalability of the image when decompressed without further processing, robustness and immunity to transmission errors, very low compression and decompression latency, and low-cost compression hardware.
Analog Devices introduced its first wavelet-based video compression IC in 1996. Since then the company has been a leading developer of JPEG2000 compression components through its Wavescale™ compression technology and now supplies the digital compression technology used by Hollywood studios for the Digital Cinema Initiative (DCI), a move to distribute feature films worldwide electronically and eliminate the production and shipping of reels of film. Recently, Analog Devices began applying that same digital compression technology to HDMI™ (High-Definition Multimedia Interface™) systems, enabling wireless transmission of HD quality video within the home. In the near future, ADI's Wavescale compression technology will allow users to enjoy the same HD image quality anywhere in their homes without the cost or complexity of running cables to every room.
A second challenge ATV designers face in the video realm is establishing compatibility across a wide variety of legacy signal types still supported in today's HD systems. Many consumers, for example, want to replay old movies, VHS tapes or use older DVD players with their new HDTVs. But many legacy standard-definition video sources are of marginal quality; what looked okay on a 27" standard definition display may look terrible on a 50" HDTV. High-performance analog signal processing based on high-resolution data conversion and advances in video filtering play a key role in bridging the gap between these technologies and letting users enjoy content from a variety of sources on an HDTV system while minimizing disturbing artifacts.
To address this problem, Analog Devices has developed an unmatched catalog of video components as part of its Advantiv solutions portfolio. The company offers an extensive line of video encoder and decoder ICs that automatically digitize and convert SDTV, EDTV, HDTV and PC-RGB signals for use in digital displays and meet all the standards for video transmission, re-distribution, editing and storage in professional and industrial applications. ADI's video CODECs offer designers both the performance and the flexibility to support the many analog formats that conform to international SDTV and HDTV standards.