|HDV is not a new tape size or camera design. It is a recording format that can accommodate many different types of high-definition image acquisition. The excitement surrounding HDV comes initially from the fact that the cameras are small and inexpensive.
Currently, both Sony and JVC have HDV camcorders on the market that sell in the $5,000 price range. Other companies, such as Canon, have announced they are already following suit, although at a slightly higher price.
Are these mighty-mite cameras as good as the pricier high-definition cameras such as Sony’s CineAlta line of HDCAM camcorders or Panasonic’s VariCam? You may find the answer surprising. Naturally, the $70,000 to $100,000 cameras like the ones George Lucas used to shoot the Star Wars prequels boast more robust electronic features; the lenses alone cost more than a single HDV camera. On the other hand, the little HDV camcorders can go places their big brothers can’t by squeezing into nooks and crannies, and utilizing considerably smaller cranes, dollies, and body mounts. They also offer the cost-savings of shooting to tape cassettes at one-tenth the price of HDCAM loads.
But, the question remains: How good are the high-definition images they record? Rental facilities can’t keep HDV cameras in stock, and many prime-time TV shows are using them for second-unit work. Several network specials have already aired that intercut HDV recordings with HDCAM, and the list of independent feature films shot in HDV continues to grow.
Sony, being the first to market with an HDV camcorder, uses interlaced video-the same recording technique found in its consumer DV cameras. The Sony HVR-Z1U professional camcorder, for example, shoots high-definition 1080i pictures at 30fps and comes equipped with a Carl Zeiss Vario-Sonnar T 12X zoom lens.
JVC calls its approach ProHD, and the company’s GY-HD100 camcorder records a progressive version of HDV or 720p running at 24fps. This camera can be mounted with interchangeable lenses, a feature that has garnered a lot of attention from image-conscious videographers.
But under the hood, things are actually a bit different. Although Sony’s HDV camcorder can produce true 1920x1080 interlaced images, it is actually recording at only 1440x1080 on each interlaced field, and the progressive pictures from JVC are actually only 1280x720 resolution. So even though the output from those cameras matches the full-pixel count expected from 1080i or 720p high definition, there is some digital scaling going on to accomplish that resolution.
Sony’s Hugo Gaggioni, CTO of the Broadcast and Production Systems Group, says demand will continue to drive technology at Sony. “Our family of HDV products are based on 1080i/60 but we will be expanding that in the future. We feel 1080i based on the 1920x1080 pixel array produces the highest temporal resolution.”
Conversely, Dave Walton, JVC’s general manager of marketing communications, says its 720p/24 approach is designed to appeal to digital cinematographers. “Since the GY-HD100 records a 24p progressive signal, this gives you the ability to have much more solid still frames without interlace jitter, while giving you a more film-like look to the high-definition recordings. You can view this progressive recording on any high-definition display, or the camcorder’s composite video output will provide a 30fps standard-definition signal for viewing on conventional NTSC monitors.”
The trick, of course, is squeezing the high-definition signal onto that tiny 6mm mini DV tape. After all, uncompressed 720p and 1080i high-definition clocks in at about 1.5Gb/sec, yet the 30fps Sony version of HDV runs at around 25Mb/sec. JVC’s 24fps variety uses only a 19Mb/sec data stream. The magic lies in what the HDV consortium did with the structure of MPEG-2 compression. Instead of each video frame having its own identity, it spreads the information over an MPEG-2 Group of Pictures, or GOP, that can be up to 15 frames long. And the reality is that some of those frames don’t really exist outside of the GOP itself. There are “I” frames, which “initiate” the GOP, “P” frames that “predict” what is to come, and “B” frames that look “bi-directionally” to increase the encoding efficiency.
|The new Avid Express Pro 5.2 is now part of the native HDV editing wave, allowing users to mix different high-definition formats with HDV on the same timeline.
HDV is easy to record, but how do you take something that may not “actually” be there into postproduction? The easiest way is to convert it into something that any conventional HD system can handle. During the last two years several companies have made video boards available that can use HD-SDI to crank up the scrawny HDV signal into full-bandwidth high definition that could be imported into many HD graphics and editing systems. New developments emerged at IBC2005 this past September that offer many new options. For example, AJA Video introduced its Kona LH board that lets you convert from HDV into Sony’s HDCAM or Panasonic’s DVCPRO HD format directly on a single PCI card.
There have been several editing systems, such as Adobe’s Premiere Pro, Canopus’s EDIUS, Sony’s Vegas, and Leitch’s VelocityHD, that provide the option of transcoding HDV into proprietary file formats for easier editing. While these file formats often have the advantage of increasing the amount of available chrominance information in the signal for tighter compositing, they also require far more storage space because they sacrifice HDV’s inherently efficient datastream.
To keep things simple and maintain HDV’s cost-efficient potential, you can manipulate HDV without conversion by staying “native.” Many of the major editing system manufacturers have been chasing themselves in an effort to provide solutions for cutting the long GOP format without conversion. Pinnacle Systems was the first to demonstrate native HDV editing with its Liquid Edition nonlinear editing software during NAB2004. Using a combination of a DirectX 9 GPU and the workstation’s own CPU, the system could handle up to four layers of HDV in real time.
A year later, Apple wowed the crowds at NAB2005 with Final Cut Pro 5 software, invoking the new architecture of QuickTime 7 to decompress and reconstruct the long GOP cadence at the cut point. The Final Cut Studio software suite even included DVD Studio Pro 4, which could output an edited HDV program to disk for playback on a Macintosh G5 workstation.
Avid Technologies recently released Version 2.2 of its Avid Media Composer Adrenaline HD and Version 5.2 of its Avid Xpress Pro systems, allowing users to leverage its DNxHD codec to mix different HD formats with HDV on the same timeline. The codec also gives you the flexibility to distribute mastering-quality HD over a network designed for SD video throughput.
Still, the bottleneck to mainstreaming HDV production remains. What do you do with that trickle of a datastream once you have finished posting it? Bumping back up to broadband HD would defeat the purpose, yet consumer-level playback devices have not been available-except for the aforementioned Macintosh G5 disk option. That is, until now.
JVC has released its new SRDVD-100U ProHD disk player priced at just $400. Now you can save your HDV projects on an inexpensive recordable DVD disk with any standard DVD burner and get up to 30 minutes of full HD playback on a 4.7gb single-layer disk or 60 minutes on dual-layer DVDs.
And, increasingly, you can find HDV aficionados streaming their clips over the Web. There are several codecs that can facilitate this, but one of the best is free-the VLC Media Player, which is available for almost any operating system from the VideoLAN Web site at www.videolan.org.
So now if you decide to catch a ride on the HDV wave, you can shoot affordably with the new HDV camcorders, post in a native format, and distribute your HDV productions to anywhere in the world. It’s a wave that is bringing high-definition production capabilities to everyone.
Jay Ankeney is a freelance writer, editor, and postproduction consultant living outside of Los Angeles.