DV

DV is a video format launched in 1996, which encodes video onto tape in digital format with intraframe compression, making it straightforward to transfer the video onto computer for editing. DV tapes come in two formats: MiniDV and DV. They record digital video compressed by a DCT method at 25 Megabit per second. As a computer file, this works out to roughly 3.5 MB per second. In terms of video quality, it is a step up from consumer analog formats, such as 8mm, VHS-C and Hi-8.

Table of contents
1 Color Sampling
2 Physical format
3 Panasonic and Sony Variants
4 Other variants

Color Sampling

Because DV uses 4:1:1 sampling for NTSC (or 4:2:0 for PAL), this reduces the amount of color resolution stored. Therefore, not all analog formats are outperformed by DV. The Betacam SP format, for example, can still be desirable because it has similar color fidelity, no digital artifacts and good low-light performance.

The lower sampling of the color space is also a reason why DV is sometimes avoided in applications where chroma-key will be used. However, a large contingent feel the benefits -- no generation loss, small format, digital audio -- is an acceptable tradeoff given the compromise in color sampling rate.

Physical format

The DV format uses "L-size" cassettes, while MiniDV cassettes are called "S-size". The larger L-size cassettes can record up to two hours. Both MiniDV and DV tapes can come with a chip to store still photos; the chip can be used only if the camera in which it is placed supports the feature.

The DVC Pro format also supports a "M-size" cassette, approximately the size of a man's palm, which holds up to 66 minutes of video at the 25 Mbit/s data rate. These cassettes may also be used in DVC Pro 50 format equipment. Regardless of size, DVC Pro cassettes are marked with two numbers, such as "66/33", to indicate the reduction in recording time when used in DVC Pro 50 gear.

Panasonic has developed the "XL-size" cassette, larger than the "L-size", for use with DVC Pro HD VTRs.

MiniDV format

MiniDV tapes are 6.5 x 4.8 x 1.2 cm and hold either an hour or an hour and a half of video depending on whether the video is recorded at Standard Play (SP) or Extended Play (EP). The tapes sold for less than USD 5 a piece as of 2003.

Software is currently available for ordinary home computers which allows users to record any sort of computer data on MiniDV cassettes using common DV decks or camcorders. A 60-minute MiniDV tape will hold approximately 10 Gigabytes of data in this form of usage.

Panasonic and Sony Variants

The DV codec is also used in videotape formats intended for more advanced and entry-level professional use. Sony devised the DVCAM format, and Panasonic devised the DVC Pro format. These two formats differ from the DV format in terms of track width and tape type. As noted before, DVC Pro also has a "M-size" cassette, holding enough tape for 66 minutes of video at the 25 MBit/s data rate, and is used primarily in broadcast news operations.

DVC Pro videotape machines can play DVCAM, DV tapes, and mini-DV tapes, with MiniDV tapes requiring an adapter. Until recently, Sony DVCAM videotape machines could play DVCAM and MiniDV tapes, but not DVC Pro. This has changed in recent years, with Sony producing decks that read all formats.

Panasonic has further scaled up the DV codec to cover HDTV applications with their DVC Pro 50 (1998) and DVC Pro HD (2000) formats. DVC Pro 50 doubles DVC Pro's tape recording speed, and hooks two DV codecs in parallel to record digital video at 50 Megabit per second. DVC Pro HD increases the tape speed further, and uses four DV codecs in parallel to achieve 100 Mbit/s.

Other variants

The Digital 8 standard uses the DV codec, but uses older Hi-8 tapes for storage. This was developed by Sony to help transition users of 8mm formats to digital.


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