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DV is a format for storing digital video. It was launched in 1995 with joint efforts of leading producers of video camera recorders. The original DV specification, known as ''Blue Book'', was standardized within the IEC 61834 family of standards. These standards define common features such as physical videocassettes, recording modulation method, magnetization, and basic system data in part 1. Part 2 describes the specifics of 525-60 and 625-50 systems.〔(Recording – Helical-scan digital videocassette recording system using 6,35 mm magnetic tape for consumer use )〕 The IEC standards are copyrighted publications available for purchase from IEC or ANSI. In 2005, DV was superseded by the successor format HDV, which used the same tape format with a different video codec. Some cameras at the time had the ability to switch between DV and HDV recording modes. == DV compression == DV uses lossy compression of video while audio is stored uncompressed. An intraframe video compression scheme is used to compress video on a frame-by-frame basis with the discrete cosine transform (DCT). Closely following ITU-R Rec. 601 standard, DV video employs interlaced scanning with the luminance sampling frequency of 13.5 MHz. This results in 480 scanlines per complete frame for the 60 Hz system, and 576 scanlines per complete frame for the 50 Hz system. In both systems the active area contains 720 pixels per scanline, with 704 pixels used for content and 16 pixels on the sides left for digital blanking. The same frame size is used for 4:3 and 16:9 frame aspect ratios, resulting in different pixel aspect ratios for ''fullscreen'' and ''widescreen'' video.〔(【引用サイトリンク】title=Digital Video and Field Order )〕 Prior to the DCT compression stage, chroma subsampling is applied to the source video in order to reduce the amount of data to be compressed. Baseline DV uses 4:1:1 subsampling in its 60 Hz variant and 4:2:0 subsampling in 50 Hz variant. Low chroma resolution of DV (compared to higher-end digital video formats) is a reason this format is sometimes avoided in chroma keying applications, though advances in chroma keying techniques and software made producing quality keys from DV material possible.〔(fxguide.com )〕〔(【引用サイトリンク】title=The DV, DVCAM, & DVCPRO Formats -- tech details, FAQ, andlinks. )〕 Audio can be stored in either of two forms: 16-bit Linear PCM stereo at 48 kHz sampling rate (768 kbit/s per channel, 1.5 Mbit/s stereo), or four nonlinear 12-bit PCM channels at 32 kHz sampling rate (384 kbit/s per channel, 1.5 MBit/s for four channels). In addition, the DV specification also supports 16-bit audio at 44.1 kHz (706 kbit/s per channel, 1.4 Mbit/s stereo), the same sampling rate used for CD audio. In practice, the 48 kHz stereo mode is used almost exclusively. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「DV」の詳細全文を読む スポンサード リンク
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