Sustainability of Digital Formats: Planning for Library of Congress Collections
Sustainability of Digital Formats: Planning for Library of Congress Collections |
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | DV, DVCAM, DVCPRO (family of related formats) |
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| Description |
For the purposes of this Web site, this family of related formats is described together, emphasizing the underlying encoding as it may be stored in media-independent files. The DV video format, however, was developed in the early 1990s as a media-dependent videocassette format. DV video signals are compressed using discrete cosine transforms (DCT) within each frame, like the the approach used with JPEG_DCT. DV does not use frame-to-frame temporal encoding like that employed by MPEG-2 and other MPEG formats. In the years after its introduction, similar but higher quality elaborations were offered by SONY (DVCAM) and Panasonic (DVCPRO, DVCPRO-50, DVCPRO HD), and these have found their place in professional television production. DV signals are formatted for transfer between devices in 80-byte blocks referred to as DV-DIF data (DV Digital Interface Format), and these DV-DIF blocks can be stored as files in raw form (.dv or .dif extension) or wrapped in such file formats as AVI, QuickTime, and MXF. Comments on this format description are welcome. |
| Production phase | Generally a initial-state or middle-state format. |
| Relationship to other formats | |
| Contains | DV-DIF, Digital Video Digital Interface Format |
| LC experience or existing holdings | Experience and holdings of DV in file form not investigated at this time. Videocassettes of DV, DVCAM, and DVCPRO formats are represented in the collections of the Motion Picture, Broadcasting and Recorded Sound Division. |
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| LC preference | None established |
| Disclosure |
Open standards. Initial specification developed by a consortium of ten companies and standardized by the International Electrotechnical Commission (IEC); elaborations developed by SONY and Panasonic and standardized by the Society of Motion Picture and Television Engineers (SMPTE). |
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| Documentation |
Using shorthand borrowed from SMPTE specification 383M (Material Exchange Format (MXF) -- Mapping DV-DIF Data to the MXF Generic Container, p.2), the documentation for the three compression specifications is as follows. Full citations are provided in Format specifications below. Comments on this information are welcome.
Additional specifications that pertain to the broad class of DV formats are listed in Format specifications below. |
| Adoption | For videocassettes, DV, DVCAM, and DVCPRO are widely adopted. DV incorporated in files is also widely adopted. Public television station WGBH (Boston) reports that DVCPRO-50 files are regularly used for program masters. Apple ships the DVCPRO-50 and -100 codecs with their Final Cut Pro editing product. Filmmakers who shoot their productions on DV often use DV-25 wrapped in MOV as a de facto preservation format. Using DV in this way has the virtue of relatively small file size which is beneficial to the low- to no-budget filmmaker. The extent of file-based adoption of DVCAM is not known to the compiler of this page; comments are welcome. |
| Licensing and patents | None identified. |
| Transparency | Depends upon algorithms and tools to read; will require sophistication to build tools. |
| Self-documentation | Generally pertains to the file format that wraps DV-DIF. However, embedded metadata may be present; see Digital Tape Preservation Strategy: Preserving Data or Video?: "DV attaches metadata to every recorded frame that can tie that frame to its place in the production chain." |
| External dependencies | None for files; many DV, DVCAM, and DVCPRO content items are recorded on videocassettes specified for those formats |
| Technical protection considerations | Pertains to the file format that wraps DV-DIF. |
| Moving Image | |
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| Normal rendering | Good support. |
| Clarity (high image resolution) |
According to the article Why Video Bit Depth Matters DVCPRO-50 and DVCPRO HD both carry 8 bits for luma and chroma channels. |
| Functionality beyond normal rendering | Not investigated at this time. |
| Sound | |
| Normal rendering | Not investigated at this time. Adam Wilt discusses the impact of locked and unlocked audio on the synchronization of picture and sound. Locked audio is preferred and offered by DVCAM and DVCPRO. |
| Fidelity (high audio resolution) | Good to excellent. PCM audio with sampling up to 48 kHz and word length up to 20 bits. |
| Functionality beyond normal rendering | Not investigated at this time. |
| Tag | Value | Note |
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| Filename extension | See related format. | See DV-DIF |
| Internet Media Type | See related format. | See DV-DIF |
| General | |
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| History |
Adam Wilt's DV, DVCAM, DVCPRO Formats-FAQ-technical (http://www.adamwilt.com/DV-FAQ-tech.html) and Internet Request for Comment (RFC) 3189, RTP Payload Format for DV (IEC 61834) Video, are the sources for much of the following: There are two kinds of DV, one for consumer use and the other for professional. In 1992, AVC-Matsushita (now Panasonic) disseminated a Blue Book pertaining to the format. In 1995, SONY introduced the DV camcorder. In 1998, the original "DV" specification (based on the Blue Book), oriented toward consumer-use digital VCRs, was published as IEC 61834; part 2 specifies the video coding as well as many other elements. The specifications for professional DV were published as SMPTE 306M (1998) and 314M (1999); these two encoding formats are based on consumer DV and used in SMPTE D-7 and D-9 video systems. By and large, the preceding developments were framed in terms of videocassette media. The RTP payload format specified in RFC 3189 (2002) supports IEC 61834 consumer DV and professional SMPTE 306M and 314M (DV-Based) formats. For several years, many DV devices have provided interfaces such as IEEE 1394 (Firewire) in order to facilitate the movement of video streams into computer files. Increasing interest in media-less handing of the bitstream has led to developments like Panasonic's P2 solid state memory format cards, featured at the National Association of Broadcasters (NAB) trade show in 2005. |
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