The HD trend: flexibility. This Panasonic AG-HVX200 camcorder records in a variety of formats.
The buzz at NAB2005 involved two converging themes: IT and HD. The information technology revolution is gobbling up what is left of traditional video-centric products targeted at broadcasters and the “new media” professionals that now dominate NAB attendance. Driven by massive volumes and the reality that HD video is just another form of data to be processed, products based on IT technologies now dominate the show floor. Computers have had high-resolution progressive displays for years. Apple Cinema Displays are used routinely to create HD video programming using Apple's Final Cut Studio tools, which now include Final Cut Pro 5, Soundtrack Pro, Motion 2 and DVD Studio Pro 4. Apple boldly claims users can “edit anything,” and industry partners are stepping forward to put this claim to the test.
Coming into NAB, the HDV format was the big buzz, with Sony claiming to have shipped more than 30,000 of its three-chip 1080i HVR-Z1U camcorders. Apple announced support for long-GOP MPEG-2 editing in Final Cut Pro, the compression technology that allows HD images to be recorded at 25Mb/s onto standard DV tapes. But HDV appears to be more of a marketing term than a format, as a variety of incompatible products were announced that use long-GOP MPEG-2 to record a variety of HD formats at a variety of bit rates.
JVC introduced the GY-HD100U, an HD camcorder that uses three 1/3in progressive scan sensors to acquire images at 1280×720 at 24p. These images can be recorded on standard DV tape using long-GOP MPEG-2 compression. However, 1280×720 at 24p is not part of the original HDV specification created by JVC, Sony, Canon and Sharp. The new JVC camera is also capable of outputting 1280×720 at 60p, but this cannot be recorded using the internal DV tape drive. JVC also showed a prototype of a new HD ENG camera that will record long-GOP MPEG-2 at 25Mb/s to DV tape and at higher bits rates to a hard disk drive to support the demands of higher frame rates.
The HD camcorder creating the biggest buzz in affordable HD at NAB2005 does not use long-GOP MPEG-2 compression or tape. Panasonic showed a prototype of a P2 HD camcorder, which records a variety of HD and SD formats to solid state memory cards using the companies trio of DVCPRO intraframe codecs: DVCPRO 25 (SD 4:1:1), DVC-Pro 50 (SD 4:2:2) and DVCPRO HD (100Mb/s for multiple HD formats). The AG-HVX200 camcorder will feature three 1/3in progressive sensors. The actual sensor resolution has not been announced. Complementing Apple's edit anything theme, the AG-HVX200 supports the following formats: 1080/60i, 30p and 24p; 720/60p, 30p and 24p; and DVCPRO 50, DVCPRO or DV (480i); and 720p mode (in which it may also capture at variable frame rates like Panasonic's Varicam).
Broadcast Engineering will provide more detail on these and other HD camera/camcorder product introductions in our June NAB wrap-up issue.
Interlace survived the transition to HD because of the difficulty and cost associated with acquiring and displaying HD images with more than 1000 lines. When the Japanese developed the 1125/60 HD systems in the late '70s, virtually all displays were CRT-based, and the scan rates associated with progressively scanning 1000 lines at 60fps were difficult to support in both professional and consumer products.
NHK, which did most of the research behind the 1125/60 system, found that a progressively scanned system with fewer lines would provide the same benefits. However, it opted for 1125 interlaced lines for many of the same bandwidth conservation reasons that contributed to the choice of interlace for the television systems we have been using for nearly a century. Interlace is a crude compression scheme that trades off spatial resolution for temporal resolution. However, modern digital compression techniques actually work better with progressively scanned sources.
Many camcorders now support the new HDV format, including the HVR-Z1U from Sony.
The ability to display HD images at these high spatial and temporal resolutions does not necessarily mean that 1080/60p acquisition and production tools are imminent, or even necessary for most applications. In reality, 720p is more than adequate for most consumer displays. The additional samples are only necessary when the screen size is larger than 70in diagonally or when the viewer is sitting close to the screen, as is the case for high-resolution computer displays.
For applications where 1080/60p makes sense, upconversion from other HD formats produces excellent results. The goal is not to present more information per se, but to eliminate the perception of the raster when it is blown up to large sizes. The ability to de-interlace video formats of various resolutions for presentation on progressive displays is one of the most important developments in the digital television transition.
Most of us still watch programs that are delivered using interlaced SDTV formats. Thus, it is critical to de-interlace this content for presentation on the wide range of new display technologies that are replacing the venerable old CRT. In addition to de-interlacing, many of these image-processing chips also perform 3:2 pulldown removal for 24p sources and other forms of advanced image processing to improve the quality of displayed images in both SD and HD.
One company exemplifies the progress that has been made in this area over the past decade. Teranex, an image processing company spun out of Lockheed Martin in the late '90s, developed a variety of image processing algorithms to run on the specialized image processing chips Lockheed developed for military applications. As the HD era began, Teranex challenged video industry veterans, such as Snell & Wilcox, with platforms to handle de-interlacing and interformat conversions. For the past three years, Teranex has been working with Silicon Optix to develop a chip capable of performing 1 trillion operations per second for both professional and consumer applications. Silicon Optix acquired Teranex last year, and the companies introduced the Realta chip at CES. The chip is being designed into several upscale consumer products, offering the same capabilities to consumers that broadcasters paid six figures for at the turn of the century.
On a similar note: Faroudja, now a subsidiary of Genesis Microchip and Gennum, has also introduced powerful new image processing chips that are capable of converting virtually any video source to 1080/60p.
There has been much progress in the realm of high-resolution image acquisition and display as the IT revolution gobbles up the world of video as we know it.
Craig Birkmaier is a technology consultant at Pcube Labs, and he hosts and moderates the OpenDTV forum.
Faroudja DVP-1080 HD Digital Video Processor
Gennum GF9330 High Performance SDTV/HDTV Deinterlacer
Silicon Optix Realta chip with Teranex Hollywood Quality Video
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