Is DV Dead?

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Table 1:ATSC Table 3, defining HD standards
Table 2:Number of CCD elements required for an HDimage

JVC has announced the JY-HD10, the pro version of the consumerGR-HD1, which will be available in May and cost less than $4,000.

Is DV dead? That's the question being asked on video-orientedlistservs since JVC demonstrated its GR-HD1 consumer HD camcorder atthe Combined Exhibition of Advanced Technology (CEATEC) show inOctober. JVC's professional products division has announced theJY-HD10, its version of the consumer GR-HD1. The JY-HD10 includes adual XLR adapter (integrated into the handle) with a mount for ashotgun mic. It will sell for less than $4,000 and be available inMay.

The approximately 3lb. camcorder has a high-quality, all glass, 10X(f = 5.2mm-52mm) zoom lens with an optical image stabilizer. Whenshooting HD, the effective 35mm range is 40.3mm to 403mm. (GL-V07520.7X and GL-V1452 1.4X lens adapters are available.) The f1.8 to f1.9lens has a 52mm filter mount. The JY-HD10 employs a single 1/3in.,1.18-megapixel CCD capable of generating both interlace and progressiveimages.

The JY-HD10 supports three recording modes: 4:3/true-16:9 NTSC DV;16:9 SDTV (480p60) MPEG-2; and 16:9 HDTV (720p30) MPEG-2. When in DVmode, both 32kHz 12-bit and 48kHz 16-bit PCM recording are used. In theMPEG-2 modes, stereo audio is recorded at a data rate of 384kbps usingMPEG-1, Layer-2, 48kHz, with 16-bit sampling. Audio levels are visibleon the LCD monitor. In all modes, the signal is recorded to standardminiDV tape.

The 0.44in. color LCD viewfinder has 113,300 pixels, while theflip-out 3.5in. polycrystalline silicon LCD has 200,000 pixels. Thecamera's grip rotates 90 degrees for low-angle shooting. JVC claims abattery life of slightly more than one hour when shooting HD.

JPEG compressed still pictures can be recorded to an SD memory card.Four image capture resolutions are supported: 620×480,848×480, 1280×720, and 1280×960. Up to 23 pictures at1280x960 can be recorded to an 8MB card.

A YPbPr cable supplies analog component output for all recordingformats. You can choose to output 480i/480p/720p (720p29.97 isupconverted to 720p59.94); 480p59.94 and 720p29.97 upconverted to1080i; or downconvert all to 480i. Downconverted video is output on thecamcorder's composite and S-Video jacks, and downconverted video can beletterboxed for display on 4:3 monitors.

An i.LINK connector inputs and outputs either DV25 or MPEG-2-TS(transport stream) data. Unlike when using analog component output,720p is output as 720p29.97 video. A headphone jack and a microphonejack (not XLR) are available on the camcorder.

The camcorder has an “AV/S” connector (composite video,S-Video input/output, stereo audio input/output, and edit control) plusconnectors for external DC power and USB. Also included with thecamcorder: a CD-ROM with application software, shoulder strap, lenscap, editing cable, USB cable, a YPbPr component analog output cable,and an A/V cable. Neither SD nor HD can be recorded from an analogsource.

Although the camcorder has a built-in edit controller, it functionsonly for DV recordings. Thus, it will not be possible to assemble-editfrom the JY-HD10 to a JVC D-VHS deck. However, you can clone MPEG-2-TSsegments to and from D-VHS.

Of course, while JVC is the first to announce a consumer HDcamcorder, I'm certain we'll see announcements from other manufacturersduring the year. This story is about more than a single product. JVC'sannouncement has raised important questions for those buying DVequipment. Few of us can forget how quickly the DV format, withFireWire, penetrated the intended prosumer market, as well as theindustrial/broadcast market.

I've seen the same four questions repeatedly asked on the Internet:Can a camcorder that uses miniDV tape record “true” HD? Cana single-chip camcorder provide quality high enough to justify HDrecording? How is it possible that an HD camcorder can be sold forapproximately the price of a DV camcorder? How can an MPEG-2 recordingbe edited?

Since the first question must be answered before the other threehave any relevance, let's start there. To answer it, let's look at aportion of the ATSC table that defines what's HDTV in the UnitedStates.

Above, text in green provides information about the two HDTVstandards used for broadcasting. The critical parameters defining thesestandards are their aspect ratios (16:9) and their resolutions —720 lines and 1080 lines. If a signal has these parameters and has aframe-rate of 24fps, 30fps, or 60fps, it is HDTV. And clearly, the720p30 signal recorded by the JVC camcorder (indicated in blue) meetsthe ATSC requirements for HDTV.

The 720p30 temporal rate is half that of 720p60. While many willreject video with such low temporal resolution, others will embrace itas providing an inherent film look. JVC has not announced a Europeanversion that offers 720p25.

The FCC limits DTV (8VSB) bandwidth to 6MHz, which allows a maximumdata rate of 19.4Mbps. Prior to broadcast, 1080i video undergoes abit-rate reduction of 70:1 to about 18Mbps. Bit-rate reduction isprimarily accomplished by MPEG-2 compression. The 720p60 image datarate is slightly less, at 16Mbps. To these image data rates, the AC-3(Dolby Digital) data rate of 384kbps is added to generate the“program” data rate.

Note that compression ratios can be increased or decreased basedupon application requirements. For example, 720p60 broadcast programdata rates can range from 18Mbps (equal to 1080i) to 15Mbps (allowingthe multicast of a 3Mbps SDTV subchannel). Pre-recorded D-VHS-HDD-Theater tapes from movie studios have a data rate of up to 28.2Mbps.They reportedly offer picture quality nearly equal that of uncompressedD-5 HD recordings of feature films.

All these data rates are easily recorded to miniDV tape. Such lowdata rates are possible because DV uses intra-frame compression, whileMPEG-2 employs inter-frame compression.

Inter-frame compression is efficient because of its use of P and Bframes in addition to I frames. P frames are based upon the previous Iframe or P frame, while B frames are based on the previous andfollowing P or I frame. As I frames are spaced farther apart and Bframes — and to a lesser extent P frames — are placedbetween I frames, image quality remains nearly constant while the datarate is reduced. Typically, I frames occur every 15 frames, as shown inthis sequence: IBBPBBPBBPBBPBB. The number of frames until the next Iframe is the GOP (group of pictures) length.

To facilitate the editing process, a short, “closed” GOPstructure can be employed. For the JY-HD10, JVC chose to use asix-frame GOP — IBBPBB. With a 15-frame GOP, there are two largeI frames for every second of video. But with a six-frame GOP, there arefive large I frames per second. A short GOP, plus the use of CBR ratherthan VBR encoding, requires a significant increase in the data rate tomaintain image quality.

The table to the left shows the number of CCD elements required for720-line and 1080-line HD for both 16:9 and 4:3 aspect ratio CCDs.

With a 16:9 chip, a DV recording is obtained by switching betweentwo windows: a 480×720, 4:3 window and a 480×720, 16:9window. Each window is centered vertically and horizontally on the CCD.The entire chip is used to obtain a 720p or 1080i image. Using a 4:3chip requires switching amongst three windows. A 4:3, 480×720window and a 16:9, 480×720 window are used for DV recording. Thesewindows are centered vertically and horizontally on the CCD. A third16:9 window is used to obtain either a 720p or a 1080i image. Unlikewith a 16:9 chip, while this window uses the entire chip's width, itdoes not fill the height of the CCD.

Because 4:3 chips are in mass production, they are the naturalchoice from a cost basis. The lowest-resolution CCD that can provide a4:3/16:9 NTSC DV image, a 16:9 SDTV image, and a 16:9 HDTV image is a1.23 megapixel chip. This resolution is easily available today.

Sony's DCR-IP220 MicroMV camcorder has a 2.1-megapixel CCD, whileJVC's GR-DV3000U DV camcorder uses a 1.33-megapixel CCD. The JY-HD10employs a 1.18-megapixel CCD (effective 1.14 megapixels) that provides840,000 pixels, rather than the 921,600-pixel image normally used for720p. Thus, a CCD row has only about 1,166 elements, which isreasonable given that the necessary (for a single-CCD camera) opticaland electrical antialiasing filters limit effective horizontalresolution.

While pro videographers may find the use of a single CCD worrisome,those who own a digital camera have few such concerns because we knowthey deliver excellent color quality. Nevertheless, it is true thatwhile a single CCD delivers two luminance samples for each cluster offour filtered CCD elements, the chip is able to provide only a singlered, green, and blue sample from the cluster. The JVC CCD is a newdesign that uses white, green, cyan, and yellow filters to delivermaximum effective vertical resolution.

The 2:1 ratio of luma samples to chroma samples is not thatsignificant because both DV and MPEG-2 compression use colorsubsampling that reduces chroma resolution even further. NTSC DVcompression uses 4:1:1 sampling, while HD MPEG-2 compression uses 4:2:0sampling.

The bulk of any camcorder includes the CCD(s), zoom lens, the cameracontrol microprocessor, analog I/O circuitry, i.LINK interface,microphone, audio DSP, and the recording mechanism. The significant newcomponents for an HD camcorder include: a better lens, opticalstabilization (necessary to avoid the even higher resolution CCD thatwould be needed for electronic stabilization); a high-resolutionviewfinder; and an MPEG-2 codec.

The image DSP must, of course, be enhanced to deal with agreater-than-NTSC frame rate (480p60 mode) and a much larger image(720p30 mode). And here, I believe, lies one reason for limiting theJY-HD10's frame rate to 30fps. An NTSC DSP chip must handle 10.4megapixels per second, while a DSP chip for 720p60 must process 55.3megapixels per second. By limiting the HD frame rate to 30fps, only27.7 megapixels per second must be processed. Thus, the JY-HD10's10-bit video DSP is not too costly for a consumer camcorder.

Lowering the frame rate to 30fps reduces the data rate flowing intothe MPEG-2 encoder by 50%, which could allow an image-recording datarate of only 8Mbps. However, because of the use of a six-frame GOP, JVCset the image data rate to 18.6Mbps to provide maximum image quality.Therefore, the total program data rate recorded to tape is 19Mbps.

MPEG-2 has a reputation as a very difficult format to edit. JVC'ssolution is state of the art. The JY-HD10 sends an MPEG-2-TS bitstreamdirectly to a computer's i.LINK connector. JVC supplies four Windows XPapplications:

1. The i.LINK I/O utility writes MPEG-2-TS data to disk files. It canalso be used to write MPEG-2-TS productions to a JY-HD10 or any JVCD-VHS deck. Supported decks include the HM-DH30000 deck and also thenew SR-VD400US. Both D-VHS and JY-HD10 tapes are structured asMPEG-2-TS data.

2. The audio utility converts Windows audio formats to and from MPEG-1Audio Layer-2 audio files so that background music and sound effectscan be added to videos.

3. MPEG Edit Studio Pro 1.0 LE was developed by the R&D labs ofKDDI in Japan. The software provides frame-accurate nonlinear editingof SD and HD MPEG-2 files. Edit Studio can import captured MPEG-2-TSfiles and MPEG-1 Audio Layer-2 audio files. Both titles and simpleeffects can be added. According to JVC, video inserts and audio insertscan also be performed. Edit Studio Pro generates MPEG-2-TS files thatcan be opened by the i.LINK I/O utility.

   Edit Studio also generates MPEG-2-PS (program stream) files for useby Image Mixer DVD. Edit Studio Pro requires a 1.3GHz Pentium 4 (2GHzor greater recommended). No Mac version of this software isplanned.

4. Image Mixer DVD creates productions and burns them to DVDs. TheseDVDs can be played in any DVD player, but the intention is that theywill be played on a DVD player with progressive output and displayed ona 16:9 progressive presentation device. Obviously, the creation of HDDVDs is not yet possible. When HD-DVD burners become available in thefuture, they will open the doors to low-cost HD production.

Of course, more professional production alternatives will bedeveloped by third parties. Windows XP has an i.LINK DirectX driver forthe HM-DH30000 D-VHS deck. Also, public domain software exists thatwill input and output an MPEG-2-TS bitstream via an i.LINK port.There's no reason to believe the JY-HD10 will not get similar softwaresupport, including applications for OS X.

If an MPEG-2-TS decoder and an MPEG-2 encoder were included on a PCIcapture board with i.LINK input, it would be possible torealtime-convert source tapes to I-frame MPEG-2 during capture. Thesecomponents could be supplied in a box with i.LINK in and out ports.Both options would merge perfectly with Apple's work with Panasonic tosupport DVCPRO 50 and DVCPRO HD (I frame, MPEG-2) in Final Cut Pro.

Those of us who worked with fragile Hi8 tapes often bumped ouracquisition format to an editing format. The same can be done withprosumer HD. A converter, such as AJA Video's HD10A, would transcodethe 720p60 or 1080i analog component signal output by the JY-HD10 touncompressed HD SDI. Even better would be a transcoder that inputs720p30 MPEG-2-TS via i.LINK, and then uncompresses and outputs thevideo as 720p60 or 1080i via HD SDI. In either case, the HD SDI signalcan be recorded by a D-5, HDCAM, or DVCPRO HD deck — or captureddirectly into a computer.

So is 25Mbps DV dead? Personally, the answer is yes. Like others nowused to watching primetime TV, movies, and sports in HD, I've foundNTSC simply doesn't have the resolution necessary for viewing on alarge screen. I'm looking forward to shooting widescreen in a formatthat will look great on a big screen. Clearly, JVC is betting that I'mnot the only one who feels this way.

By supplying HD acquisition, editing, distribution, and presentationproducts, JVC is also positioned to provide a low-cost HD solution tomarkets such as medical education, marketing, museums, and aquariums.And I expect that prosumer HD will be adopted by the indie filmcommunity. I see the next digital revolution coming — fast.

Steve Mullen is owner of Digital Video Consulting, which providesconsulting and seminars on digital video technology. His website can befound at www.mindspring.com/~d-v-c.

To comment on this article, email the Video Systemseditorial staff at vsfeedback@primediabusiness.com.

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