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What is HDV?

What is HDV?

Hi-Def has become the big catch phrase of the year, but many people don't understand just what the format is and why it will be so important to our TV viewing future.

In the first television revolution since the 1950s, 2006 will mark the year when America goes digital. In that year, by government mandate, digital television (DTV) and HDTV (high definition) will be a reality. Of course, many Americans will upgrade to widescreen high definition TVs over the next few years as the prices come down.

Once HD is firmly implanted in America's living rooms, there will be a demand for content. Once the djinn is out of the bottle, there's no going back: Television just won't look the same. In fact, there is a demand for HD today, from major networks and even local PBS affiliates. However, professional HD production equipment is priced at many thousands of dollars, far out of reach of most American videographers.

In September of 2003, Canon, Sharp, Sony and JVC announced they would work together on a home High Definition Video (HDV) standard. HDV allows high definition video to be stored on an ordinary DV or Mini DV tape. JVC has already come out with two cameras, Sony's announced a third and various editing solutions are already on the market, all within the price range of prosumer videographers.

How does it work?

HDV stores 16:9 high definition video on DV tapes, supporting both 720p and 1080i (NTSC and PAL), using MPEG-2 compression for data rates of 19Mbps and 25Mbps respectively, comparable to the bitrates of ordinary DV (25Mbps). Audio is compressed by 75% using MPEG-1 Layer 3.

Too good to be true?

Is this too good to be true? Well, sort of: There is a catch. The video streams over FireWire using an MPEG-2-TS (or "Transport Stream") format. This is a compressed format, which is incompatible with most DV editing software. MPEG compresses clusters of video frames (GOP or group of pictures) together into one stream for delivery. By taking advantage of the similarities between frames (after all, if the sky is blue in frame 1, what color is it likely to be in frame 2?) and compressing them together, MPEG is able to provide significant space saving. This also means that frame-accurate editing is difficult, to say the least. The computer must decompress each group of frames and then the whole thing re-compressed, even for simple timeline previews. MPEG, remember, is also a loss-y compression algorithm, so you can't just keep compressing and decompressing it. Multiple rendering and re-rendering of the video will produce compression legacies that get worse and worse. MPEG also bundles (i.e. muxes) the audio into the compression stream. All this means is it's difficult to edit with traditional editing tools.

Digital TV Formats, a Primer

The resolution of a TV image directly affects how sharp it looks. Higher resolutions provide more detail. An SD (standard definition) NTSC television frame (such as the one you watch every night) is made up of 525 horizontal lines broken up into two fields. The first field is made up of the odd lines and the second field is made up of the even lines. This is what we call interlaced video.

Of these 525 lines, only about 480 actually make it onto a normal television screen (the other lines are used for synchronization, closed captioning information and some are just plain masked). The horizontal resolution is how many dots each of those 525 lines can have going across. The resolution of a TV image is determined by the "circle rule" or the number of dots across the largest circle which can be displayed on the television. On a standard 4:3 TV, a circle will fill about 75% of the display. On a 16:9 formatted HDTV, the circle will fill about half the screen. According to the circle rule calculation, NTSC video has a resolution of about 330. A VHS tape has about 240 lines of resolution. DVDs have about 480 lines of resolution, which is the highest resolution a standard TV can display. High Definition televisions on the other hand, can display 1080 lines of vertical resolution, twice that of an ordinary TV and three times as much as broadcast television.

More on Interlacing

Technology has improved drastically since the creation of the 50-year-old NTSC standard used in television today. It's now possible to show all the information in a video frame at once, instead of only half a frame at a time (interlaced). This is progressive scan and provides a sharper image than interlaced scans.

Interlaced and progressive are represented by a lowercase "i" or "p". So, when you see a format described as 720p it means "720 lines of resolution in a progressive scan."

HD formats are broken down into five categories:

  • 480i: The digital version of a standard definition TV image. 704X480 resolution at 30 fps, 60 fields per second, interlaced.
  • 480p: A progressive scan version of the standard TV image.
  • 720p: Widescreen progressive scan with 720 lines of resolution. 1280X720 at 30 or 60 fps.
  • 1080i: Widescreen interlaced. 1920x1080 resolution 30fps, 60 fields per second.
  • 1080p: The Holy Grail of High Definition: 1920x1080 resolution at 30 or 24 (film) fps, progressive scan, rarely seen off the computer desktop where it is currently supported by Windows Media Player 9.

What Exists now?

A great idea is only as good as what's shipping. Here's a quick look at cameras, editing, and playback technology you can buy today.

Cameras

In September 2003, Canon, Sony, Sharp and JVC all announced their support for the HDV format. JVC was the first out of the gate with a pair of cameras, the professional class JY-HD10U and the consumer grade GR-HD1.

Sony is also in the mix with the HDR-FX1, which is a 3-CCD prosumer model priced at about $3,700. With three cameras on the market, it looks like the camcorder industry is serious about backing this format.

Editing

There are several editing systems for the HDV format. On the Mac, Final Cut Pro HD is not an HDV compatible version editing software. Out of the box FCP HD can capture, edit and output DVCPro HD, DV and SD, but not HDV. Look for more third-party solutions in the immediate future.

For Windows, CineForm has a trio of HDV editing tools, Prospect, Aspect, and Connect. All are centered around a codec which converts HDV MPEG into Windows AVI encoded video, which many programs can edit. After passing through the CineForm codec, the video bloats to four times its original size, but this allows users to utilize software they're already familiar with. CineForm also has a custom rendering engine plug-in that works with specific applications (e.g. Premiere) to provide realtime software previews.

Ulead has a $299 plugin for MediaStudio Pro 7 that allows the importing of HDV. Instead of converting the video to a new format, the way the CineForm software does, Ulead keeps the video in the MPEG format. This is good, in that you don't need to perform a conversion, but it also means that it is more difficult for the computer to edit the video.

Turnkey HD Systems

There are a number of turnkey vendors who are also offering HD solutions. DV411 (www.dv411.com) is offering a complete HDV turnkey system including camera, editing station, and burner for about $7,000. The bundle includes a ProEdit eX P4 Workstation, a JVC JY-HD10U Camera, Ulead's Studio Quartet software bundle with the HD Plugin and an HDV training DVD. Boxx Technologies (www.boxxtech.com) offers a variety of turnkey systems made up of its own computer, JVC Camera, Adobe Premiere and the CineForm software. We expect most turnkey vendors to offer similar packages as user demand increases.

How Do I Get HDV to Play on My HDTV?

You've got an HDV camera and an HDV editing computer, so you make the most marvelous HDV movies. How do you play them back on your HDTV? You can play them back directly from the camera (you already knew that) or you can play them back from a D-VHS (Digital VHS) deck (from JVC, of course). You can also playback HDV on a desktop or laptop computer and if you have a high quality projector, you can show your HDV on a wall or movie screen. One of the most popular solutions will be to create DVDs, but, as you now know from our discussion of resolution, DVD is not HD, so you will sacrifice some quality and image size.

Conclusion

HDV has proven that it is functional, that it looks great during production, editing and when played back. What it has yet to prove is longevity. In the race for standards, there are often competing formats and while there currently seems to be no viable competition for the market HDV is trying to reach, it's still early in the game.

Kyle Cassidy is a video artist and freelance writer who lives in Philadelphia with his cats Milla and Tatiana.

Tags:  December 2004
Kyle
Cassidy
Wed, 12/01/2004 - 12:00am