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MillimeterJVC GZ-HD7: World’s First 1920x1080 MPEG-2 Camcorder, Part 1
Sep 7, 2007 12:00 PM, By Steve Mullen
My JVC GZ-S3 Staticon camera and GZ-C3 VHS-C VTR circa 1983
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When I tested JVC’s DR-HD100 60GB hard-disk recorder for a review published in Broadcast Engineering (November 2006), I had the opportunity to experience both the advantages and disadvantages of hard-disk video recording. My conclusion was that the HD100 was a compromised by the need to carry it along with the camcorder. While I was happy with this kind of rig in 1983—it is not what I want today. The obvious solution is to eliminate a camcorder’s tape transport and replace it with a hard drive.
The JVC GZ-HD7 (MSRP of $1,799.95) features a three CCD imaging system.
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Imaging Technology
Each of the JVC GZ-HD7's 1/5in., 16:9 CCD has 570,000 elements that are progressively scanned every 1/60 second. Analog RGB signals from the CCDs are converted to digital data using 14-bit A/Ds. The Blue and Red CCDs are offset by one-half pixel from the Green CCD along both horizontal and vertical axes. Therefore, JVC uses the same resolution CCDs and employs similar pixel-shift technology as does Panasonic for its four-times-more-expensive AG-HVX200 P2 camcorder (click here for Barry Braverman's review of the HVX200). (The HD7’s resolution is approximately equal to the Panasonic HVX200.)
The GZ-HD7 supports three MPEG-2 encoding modes: FullHD mode records five hours of 1920x1080i VBR at up to 30Mbps (26.6Mbps average); the “HDV equivalent” mode records five hours of 1440x1080 CBR at 27Mbps (the limit of D-VHS); and the SP mode records seven hours of 1440x1080i VBR at up to 22Mbps. For the latter two modes, each line is downscaled to 1440-pixels before encoding. For more, click here.
Stereo audio is encoded as MPEG-1 Layer 2 (MP2) at 384kbps. The video and audio elementary streams are multiplexed into a Transport Stream where each Data Packet has 192 bytes rather than the 188 bytes found in M2T files. This type of stream is called M2TS and the files are given a .TOD extension. A shock-resistant 1.8in. 60GB hard disk records the data stream.
Up to 25 minutes of SP can be recorded to a 4GB SDHC card so the GZ-HD7 is able to also perform as a sold-state HD camcorder. This opens the option to record video in physically demanding situations such as skydiving.
