ProHD: a systems approach to HDV

Post, June, 2005 by Tim Tokita

When the basic specifications for the HDV format were introduced to the world on July 4, 2003, the four companies involved (Canon, JVC, Sharp and Sony) knew that this new format would revolutionize high definition recording for the consumer. Just four months earlier, JVC introduced the very affordable GR-HD1 HDV consumer camcorder. A month later, the JY-HD10 prosumer HDV camcorder was shown at NAB 2003.

The introduction HDV format, along with the availablity of the HD10, and changed the way independent filmmakers and videographers looked at high definition. This community, which is always looking to improve its image acquisition quality, suddenly had a new option, one that for the first time put the terms "high definition" and "affordable" in the same sentence.

With the ability to record with inexpensive equipment on inexpensive DV tape and edit on inexpensive editing systems, high definition was no longer just for the rich and famous. Now almost everyone could consider high definition for their projects.

At JVC, we received a great deal of feedback on the HD10 and the HDV format--what shooters wanted and what editors needed in the post environment. We began the task of professionalizing products that record in the HDV format, addressing the limitations of HDV while conforming to the spirit of HDV. We realized that if done properly, HDV could benefit the professional community the same way that professionalized DV formats have.

The result of this undertaking is ProHD--a systems approach to HDV. With ProHD, JVC follows the specifications originally released for HDV in 2003, introducing models with the features and capabilities that professionals have requested.

WHAT IS HDV?

It's important to recognize that the HDV format isn't a "tape format" in the traditional sense of the term. HDV was designed to leverage the popularity of DV and is simply a method of recording data onto a DV tape.

It is also important to realize that there are two versions of HDV: HDV1, the progressive scan version; and HDV2, the interlace scan version. These versions have three major differences: luminance sampling frequency, bit rate after compression, and MPEG-2 stream type.

For HDV1/720p, the luminance sampling frequency is 74.25MHz, while the HDV2/1080i luminance sampling frequency is only 55.7MHz. After compression, the HDV1/720p bit rate is approximately 19Mbps, while the HDV2/1080i bit rate is approximately 25Mbps. Finally, HDV1/720p uses transport stream data for recording, while HDV/1080i uses packetized elementary streams for recording. These differences will be key to professionalizing the HDV format.

REAL-WORLD USE

The biggest shortcoming of HDV products prior to the introduction of ProHD for digital cinematographers has been the lack of true 24-frame progressive high definition HD recording and interchangeable lenses. The GY-HD 100U ProHD camcorder provides for interchangeable lenses, and uses the HDV1/720p format and offers true 24p recording at 720 lines, using an MPEG-2 GoP of six frames, eliminating the need for longer GoP MPEG editors.

As videographers, cinematographers, editors and producers know, nothing really compares to the 24-frame progressive look of film except something shot, recorded, and played back in true 24-frame progressive mode.

Other ProHD enhancements include timecode with user bits, the ability to record on hard disk (with the Focus Enhancements DR-HD100), and the ability with future products to record on optical media and flash memory cards. This allows for the editing process to begin sooner without having to digitize into an NLE as the hard disk is mounted directly to on the NLE. Recording to hard disk and tape simultaneously provides producers with a take-away tape copy while providing editors with the ability to begin editing immediately.

While post production for HDV took some time to ramp up to speed, all of the editing system providers that support HDV will be including support for ProHD's 720/24p capability.

PROHD'S ROOTS

The ProHD moniker was first used in early 2003 as a way to affordably master and distribute professional high definition recordings and digital dailies. Based on JVC's D-VHS format, the professional system is built around an HD MPEG-2 encoder, recording VCR and playbck VCR.

By TIM TOKITA National Product Marketing Manager JVC Professional Products Company www.jvc.com/prof