HDV (video format)
HDV is a video format for high definition video and is a trademark of Sony and JVC .
Details
"HDV" is a video format for high amateur and corporate demands, which is increasingly finding its way into the professional broadcast segment due to cost considerations, just as it was the case with DV at the time. The technical quality is, however, inferior to professional HD broadcast formats such as DVCPRO-HD or HDCAM , whose data rates are four or six times as high and work with higher color sampling. Such a development is XDCAM HD of Sony that in three different data rates of 18, 25, 35 Mbit / s and 50 Mbit / s (XDCAM HD 422) is working and also on a MPEG-2 - Codec based. In 2011, HDV was largely superseded by AVCHD .
The DV standard and the HDV format have considerable fundamental differences and are therefore only comparable to a limited extent. While video formats according to the DV standard are based on the standard definition formats of the PAL and NTSC norms, HDV is based on the newly defined high definition standards 720p and 1080i in the 16: 9 image format .
The HDV video format was developed by Sony and JVC and is now supported by almost all video manufacturers and software providers. The recording takes place in defined formats:
- HDV1 720p: 1280 × 720 pixels with frame rates 25p or 50p in PAL countries (30p or 60p in NTSC countries) and optionally 24p
- HDV2 1080i: 1440 × 1080 pixels with frame rates 25p (sf) or 25i in PAL countries (or 30p (sf) or 30i in NTSC countries)
HDV1 uses the progressive format (“p” for short) in which a real full image is obtained at once by progressive scanning of the image sensor from top to bottom. When interlaced (English interlaced , or "i") of the HDV2 there is a "full screen" in reality consists of two half images, which are sequentially scanned and then odd the even lines of the image sensor and displayed first. The indolence of the human eye and the afterglow effects of picture tubes give the impression of a continuous image.
In the higher-resolution 1080i format, the individual pixels are not square, but anamorphic, i.e. horizontally stretched in a ratio of 1: 1.33, so that here, too, there is an image format in 16: 9.
The video data is recorded in compressed MPEG-2 format with a data rate of around 19 Mbps at 720p and around 25 Mbps at 1080i on conventional DV or HDV tapes, less often on hard disk drives (HDD) or on memory cards .
With the market launch of HDV, new tape technologies have been developed for the previous DV cassettes, which are said to have a lower error rate. This was considered necessary because a dropout on the tape would affect the subsequent images due to the MPEG-2 storage of the individual images in an interframe-based GOP structure (which could result in up to 14 images being error-prone) during storage In an intraframe-based format (e.g. DV , Digital Betacam , Digital-S, DVCPRO and DVCPRO HD) only one image or frame is affected. In practice, however, it has been found that this effect occurs much less frequently than initially feared. The actual advantage of the (considerably more expensive) special HDV compared to conventional DV cassettes is partly controversial.
The progressive recording and playback corresponds to the cinematic functionality, while interlacing corresponds to the physical conditions on picture tube televisions. The storage itself takes place here, so to speak , using the interlacing method , with the full image being stored on the tape as two (identical) easily reproduced fields (AA-BB) one after the other.
All modern "pointing devices" (ie LCD / TFT plasma monitors and projectors, "beamers") always work with full images, which makes the complex and sometimes lossy conversion of signals with half images necessary. Modern pointing devices have almost all built-in “deinterlacers”, but these often do not work optimally, especially in the consumer area (fraying effect). In order to maintain the quality, it is therefore absolutely advisable, especially with HDV, to feed full-screen signals to the pointing devices. For this reason, even modern players (e.g. DVD, Blu-ray, HDD recorder) preferably output full-screen signals.
Another improvement is the expanded “ xvColour ” color space , which allows more and “stronger” colors to be displayed using suitable displays. This virtual extension of the color space can obviously be recorded without changing the HDV format (and MPEG2 compliant).
literature
- W. Wunderlich: Digital television HDTV, HDV, AVCHD for beginners and those switching . 1st edition, Auberge-tv Verlag, Hohen Neuendorf 2007, ISBN 978-3-00-023484-2 .
- Ulrich Stöckle: HD ready or what? Tips for switching to HDTV . bhv PRAXIS, 2006, ISBN 978-3-8266-7437-2 .
Web links
- HDV Format Web Site - Official Website
Individual evidence
- ↑ HDV Format Web Site ( Memento of the original from September 23, 2004 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. - Official website (English); As of June 2, 2010
