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HDV@Work

Oct 21, 1997 4:16 PM

JVC's approach to 24p
By Steve Mullen

Support of 24p from the JVC GY-HD100 provides a perfect example of how a company's intellectual investment affects the support of a new camcorder. When the HD100 began shipping, some companies did not support its 24p mode. Suddenly explanations for why support was not available appeared on web sites. One reason advanced was that the support of 24p was very "difficult" and so it would take a long time before the JVC would be supported. Another post put the blame on JVC for “violating” the HDV specification. This claim was based upon there being no "24p specification" in the joint Sony/JVC document published in 2003. (See my article on "The ProHD Approach" in the May issue of Video Systems for more on that. Also, see the last edition of HDV@Work for an examination of Canon's approach to 24p.)

These explanations ignore the fact that HDV is built upon the MPEG-2 specification, which has always supported 24p. In fact, when we watch a movie on a DVD, the DVD player is using MPEG's ability to carry 24p video. JVC simply used a standard MPEG-2 mechanism—the Repeat Flag—to implement 24p. (Repeat Flags occupy only a few bytes in the MPEG-2 data stream. They are one of many types of “flags” used by MPEG-2.)

Incoming 24p video is processed in groups of six frames (A, B, C, D, E, and F—as shown in the Table). Each group of six video frames is encoded into a MPEG-2 GOP (IBBPBB). The encoder inserts one or two Repeat Flags (RF) between each encoded frame. Though this process, 6 frames are converted to 15 frames—6 frames of which are encoded frames and 9 of which are Repeat Flags. The pattern by which the frames are generated is a familiar one—2:3:2:3:2:3, or simply 2:3 pulldown.

A

B

C

D

E

F

A

B

C

D

E

F

I

RF

B

RF

RF

B

RF

P

RF

RF

B

RF

B

RF

RF

Record/Playback

I

RF

B

RF

RF

B

RF

P

RF

RF

B

RF

B

RF

RF

A

B

C

D

E

F

For each second of video, this process is repeated 4 times. Thereby, 24 frames are converted to 60 “frames.” Thus, the recorded MPEG-2 timebase is 720p60, although only 24 video frames are recorded to tape - with the 36 Repeat Flags. During tape playback, each of the 24 frames is decoded. When a Repeat Flag is encountered, the last frame is output again - 1/60th second after it was first output. If a second Repeat Frame is encountered, the last video frame is output again - 1/30th second after it was first output.

Through this process, 720p60 is output carrying 24p video. Because JVC uses a standard MPEG-2 feature, some hardware and software were able to support the HD100 immediately. For example, some HDTVs equipped with i.LINK/IEEE 1394 were able to correctly present 24p played back from the HD100 camcorder. Moreover, some software handled 24p without problems: CineForm's AspectHD and Sony Vegas 6, for example. Thus, it is clear that if an NLE company had fully implemented MPEG-2 when it introduced HDV support, JVC's 24p would be automatically supported.

JVC's 24p also is able to be edited as one would film. By dropping the 36 Repeat Flags within each second of HDV and transferring only the 24 remaining frames of 720p HDV video to disk, one has the video equivalent of film.

After editing 24fps, you have two options. If you want an immediate transfer to film, you can send your production directly to a film lab on a hard disk.

Alternately, you can apply reverse 2:3:2:3 pulldown to create 60Hz SD or HD video. For example, 720p60 can be recorded to DVCPRO HD via either HD-SDI or FireWire. There will, of course, be a slight loss in horizontal resolution going to DVCPRO HD.

Were the Repeat Flags not dropped, a correctly designed MPEG-2 NLE would write files of 720p60 video to disk that have a 2:3:2:3 "film transferred to video look." This video could be edited as 720p60 video.

We have clearly entered another phase of "low-cost" HD production. Now the focus has turned to creating film productions using HDV camcorders.

Focus Enhancements announces availability of HDV FireStore hard disk recorders

Focus Enhancements, Inc., a worldwide leader in video production and conversion technology, today announced that its highly anticipated FireStore FS-4 HD and FS-4Pro HD Portable Direct To Edit (DTE) disk recorders are available, through Focus Enhancements' distribution network. The new DTE video recorders are designed for HDV videographers involved in wedding and events, independent film, HD television production, corporate video, government, and education.

Focus Enhancements' groundbreaking FireStore FS-4 HD line of Portable DTE recorders is the latest extension to its industry-leading FireStore family of DTE studio rackmount, shoulder mount, and SD handheld recorders. The FS-4 HD delivers HD and DV acquisition solutions from the field to the editing room, enabling videographers to record HDV or DV streams directly to disk from leading HD video camcorders and decks including Sony's HVR-Z1U HDV camcorder and JVC's GY-HD100U ProHD camcorder via FireWire. FireStore then connects directly to Mac/Windows-based editing systems, allowing video professionals to edit content directly from the FS-4 HD. Users can choose from the most popular NLE file formats including standard-definition Avid OMF, Canopus AVI, Matrox AVI, and more, as well as high-definition 720p or 1080i MPEG-2 transport streams (.m2t).

"With the enormous success of HDV camcorder shipments, combined with the strong growth in the amount of HD footage shot and broadcast, HD is quickly emerging as the standard of choice for many different applications," said Matt McEwen, product manager for Focus Enhancements. "FS-4 HD's powerful DTE technology, rugged enclosure, and compact size make it the most complete digital recording solution for HDV and DV applications -- further extending our leadership in the disk-based acquisition market."

The new FS-4 HD DTE recorders feature a 40GB (3-hour) internal disk drive, and the FS-4Pro HD recorders offer an optional 80GB (6-hour) internal disk drive, all in a small, shockproof chassis. FS-4 HD recorders are lightweight, weighing about 1lb. including the battery, and are only 1.5-in. thick.

Videographers can easily mount the unit to their camcorder using the optional hot-shoe clip-on adapter or attach it directly to their belt. The FS-4 HD features a removable Li-Ion battery pack, 16 front panel buttons with VTR-like controls, a backlit status LCD display, multiple control modes, a six-second retro cache, user-definable function keys, extensive playback features, and support for HDV- and DV25-based DTE.

The FS-4Pro HD offers the same feature set as FS-4 HD, but also includes up to 10 seconds of retro cache, retro disk, loop record, user-definable folders for scene marking, and support for additional DV25 DTE technology file formats including Avid DV-OMF and Pinnacle AVI.

FireStore FS-4 HD, FS-4Pro HD 40GB, and FS-4Pro HD 80GB recorders are available through the worldwide Focus Enhancements dealer and distributor networks for a US MSRP of $999, $1,395, and $1,795, respectively. FireStore FS-4 SD models are upgradeable to HD in the field by purchasing a simple download for a US MSRP of $299.

For more information on Focus Enhancements and its products, please visit www.focusinfo.com.

QZEO announces new reseller agreement with JVC

QZEO, the pro broadcast reseller division of Computer Modules, Inc., announced that it has entered into an audio-video reseller agreement with JVC Professional Products Company. JVC Professional Products Company is a leading manufacturer of professional broadcast equipment.

QZEO is a leading distributor of digital video processing and capture solutions, with over 23 years of experience in providing products and audio video systems integration to broadcasters, content creators, and other industrial users. QZEO makes it easier for video professionals to combine video and computer technologies, with products that create digital video for the Internet or for professional broadcasts. QZEO's numerous digital video products are used for shooting video, editing, encoding and decoding, recording/playback, video streaming , and video storage.

Adding to its extensive product lineup, QZEO is now selling audio, professional and broadcast video, and presentation products from JVC Professional Products Company -- DV and HDV video cameras, video recorder/players and video monitors, projectors, and plasma displays.

"We're proud to sell JVC Professional Products," said Scott Grizzle, QZEO's sales engineer. "The response from our customers has been outstanding. Our many customers in San Diego and Southern California are especially impressed with the excellent production quality generated by JVC products. Our customers expect the best and most innovative video equipment available, and JVC products have a well-deserved reputation for outstanding reliability."

JVC products being offered by QZEO include the JVC GY-HD100U, a compact, full-resolution HD progressive camcorder that received an NAB Award for Innovation in Media (AIM) at NAB2005, and the BR-HD50U ProHD recorder/player -- the companion model to the GY-HD100 -- designed to transfer video and audio data to a nonlinear editing system. The BR-HD50U VTR features switchable HDV and DV modes and analog outputs.

"We're excited to be working with QZEO," stated Phil Burns, district sales manager for JVC Professional Products Company. "With QZEO's strong expertise in digital video technology and their many long-term customers, we know they'll be very successful."

Visit CMI's website at www.compumodules.com, or call (858) 613-1818. For more on JVC, visit www.jvc.com/pro.

© 2008 Penton Media, Inc.