Tag Archives: digital video

Media Recognition: DV part 3

DVCAM (encoding)

Type:
Digital videotape cassette encoding
Introduced:
1996
Active:
Yes, but few new camcorders are being produced.
Cessation:
Capacity:
184 minutes (large), 40 minutes (MiniDV).
Compatibility:
DVCAM is an enhancement of the widely adopted DV format, and uses the same encoding.
Cassettes recorded in DVCAM format can be played back in DVCAM VTRs (Video Tape Recorders), newer DV VTRs (made after the introduction of DVCAM), and DVCPRO VTRs, as long as the correct settings are specified (this resamples the signal to 4:1:1). DVCAM can also be played back in compatible HDV players.
Users:
Professional / Industrial.
File Systems:
Common Manufacturers:
Sony, Ikegami.
DVCAM is Sony’s enhancement of the DV format for the professional market. DVCAM uses the same encoding as DV, although it records ‘locked’ rather than ‘unlocked’ audio. It also differs from DV as it has a track width of 15 microns and a tape speed of 28.215 mm/sec to make it more robust. Any DV cassette can contain DVCAM format video, but some are sold with DVCAM branding on them.
Recognition
DVCAM labelled cassettes come in large (125.1 x 78 x 14.6 mm) or MiniDV (66 x 48 x 12.2mm) sizes. Tape width is ¼”. Large cassettes are used in editing and recording decks, while the smaller cassettes are used in camcorders. They are marked with the DVCAM logo, usually in the upper-right hand corner.

HDV (encoding)

Type:
Digital videotape cassette encoding
Introduced:
2003
Active:
Yes, although industry experts do not expect many new HDV products.
Cessation:
Capacity:
1 hour (MiniDV), up to 4.5 hours (large)
Compatibility:
Video is recorded in the popular MPEG-2 video format. Files can be transferred to computers without loss of quality using an IEEE 1394 connection.
There are two types of HDV, HDV 720p and HDV 1080, which are not cross-compatible.
HDV can be played back in HDV VTRs. These are often able to support other formats such as DV and DVCAM.
Users:
Amateur/Professional
File Systems:
Common Manufacturers:
Format developed by JVC, Sony, Canon and Sharp.
Unlike the other DV enhancements, HDV uses MPEG-2 compression rather than DV encoding. Any DV cassette can contain HDV format video, but some are sold with HDV branding on them.
There are two different types of HDV: HDV 720p (HD1, made by JVC) and HDV 1080 (HD2, made by Sony and Canon). HDV 1080 devices are not generally compatible with HDV 720p devices. The type of HDV used is not always identified on the cassette itself, as it depends on the camcorder used rather than the cassette.
Recognition
HDV is a tape only format which can be recorded on normal DV cassettes. Some MiniDV cassettes with lower dropout rates are indicated as being for HDV, either with text or the HDV logo. These are not essential for recording HDV video.

 

-Rebecca Nielsen

Media Recognition: DV part 2

DV (encoding)

Type:
Digital videotape cassette encoding
Introduced:
1995
Active:
Yes, but tapeless formats such as MPEG-1, MPEG-2 and MPEG-4 are becoming more popular.
Cessation:
Capacity:
MiniDV cassettes can hold up to 80/120 minutes SP/LP. Medium cassette size can hold up to 3.0/4.6 hrs SP/LP. Files sizes can be up to 1GB per 4 minutes of recording.
Compatibility:
DV format is widely adopted.
Cassettes recorded in the DV format can be played back on DVCAM, DVCPRO and HDV replay devices. However, LP recordings cannot be played back in these machines.
Users:
DV is aimed at a consumer market – may also be used by ‘prosumer’ film makers.
File Systems:
Common Manufacturers:
A consortium of over 60 manufacturers including Sony, Panasonic, JVC, Canon, and Sharp.
DV has a track width of 10 microns and a tape speed of 18.81mm/sec. It can be found on any type of DV cassette, regardless of branding, although most commonly it is the format used on MiniDV cassettes.
Recognition
DV cassettes are usually found in the small size, known as MiniDV. Medium size (97.5 × 64.5 × 14.6 mm) DV cassettes are also available, although these are not as popular as MiniDV. DV cassettes are labelled with the DV logo.
DVCPRO (encoding)
Type:
Digital videotape cassette encoding
Introduced:
1995 (DVCPRO), 1997 (DVCPRO 50), 2000 (DVCPRO HD)
Active:
Yes, but few new camcorders are being produced.
Cessation:
Capacity:
126 minutes (large), 66 minutes (medium).
Compatibility:
DVCPRO is an enhancement of the widely adopted DV format, and uses the same encoding.
Cassettes recorded in DVCPRO format can be played back only in DVCPRO Video Tape Recorders (VTRs) and some DVCAM VTRs.
Users:
Professional / Industrial; designed for electronic news gathering
File Systems:
Common Manufacturers:
Panasonic, also Philips, Ikegami and Hitachi.
DVCPRO is Panasonic’s enhancement of the DV format, which is aimed at a professional market. DVCPRO uses the same encoding as DV, but it features ‘locked’ audio, and uses 4:1:1 sampling instead of 4:2:0. It has an 18 micron track width, and a tape speed of 33.82 mm/sec which makes it more robust. DVCPRO uses Metal Particle (MP) tape rather than Metal Evaporate( ME) to improve durability.

DVCPRO 50 and DVCPRO HD are further developments of DVCPRO, which use the equivalent of 2 or 4 DV codecs in parallel to increase the video data rate.

Any DV cassette can contain DVCPRO format video, but some are sold with DVCPRO branding on them.

Recognition
DVCPRO branded cassettes come in medium (97.5 × 64.5 × 14.6mm) or large (125 × 78 × 14.6mm) cassette sizes. The medium size is for use in camcorders, and the large size in editing and recording decks. DVCPRO 50 and DVCPRO HD branded cassettes are extra-large cassettes (172 x 102 x 14.6mm). Tape width is ¼”.

DVCPRO labelled cassettes have different coloured tape doors depending on their type; DVCPRO has a yellow tape door, DVCPRO50 has a blue tape door, and DVCPRO HD has a red tape door.

Images of DVCPRO cassettes are available at the Panasonic website.

-Rebecca Nielsen

Media Recognition: DV part 1

DV can be used to refer to both a digital tape format, and a codec for digital video. DV tape usually carries video encoded with the DV codec, although it can hold any type of data. The DV format was developed in the mid 1990s by a consortium of video manufacturers, including Sony, JVC and Panasonic, and quickly became the de facto standard for home video production after introduction in 1995. Videos are recorded in .dv or .dif formats, or wrapped in an AVI, QuickTime or MXF container. These can be easily transferred to a computer with no loss of data over an IEEE 1394 (Fire Wire) connection.

DV tape is ¼ inch (6.35mm) wide. DV cassettes come in four different sizes: Small, also known as MiniDV (66 x 48 x 12.2 mm), medium (97.5 × 64.5 × 14.6 mm), large (125.1 x 78 x 14.6 mm), and extra-large (172 x 102 x 14.6 mm). MiniDV is the most popular cassette size.

DV cassettes can be encoded with one of four formats; DV, DVCAM, DVCPRO, or HDV. DV is the original encoding, and is used in consumer devices. DVCPRO and DVCAM were developed by Panasonic and Sony respectively as an enhancement of DV, and are aimed at a professional market. The basic encoding algorithm is the same as with DV, but a higher track width (18 and 15 microns versus DV’s 10 micron track width) and faster tape speed means that these formats are more robust and better suited to professional users. HDV is a high-definition variant, aimed at professionals and consumers, which uses MPEG-2 compression rather than the DV format.

Depending on the recording device, any of the four DV encodings can be recorded on any size DV cassette. However, due to different recording speeds, the formats are not always backwards compatible. A cassette recorded in an enhanced format, such as HDV, DVCAM or DVCPRO, will not play back on a standard DV player. Also, as they are supported by different companies, there are some issues with playing back a DVCPRO cassette on DVCAM equipment, and vice versa.

Although all DV cassette sizes can record any format of DV, some are marketed specifically as being of a certain type; e.g. DVCAM. The guide below looks at some of the most common varieties of DV cassette that might be encountered, and the encodings that may be used with them. It is important to remember that any type of encoding may be found on any kind of cassette, depending on what system the video was recorded on.

MiniDV (cassette)

Type:
Digital videotape cassette
Introduced:
1995
Active:
Yes, but is being replaced in popularity by hard disk and flash memory recording. At the International Consumer Electronics Show 2011 no camcorders were presented which record on tape.
Cessation:
Capacity:
Up to 80 minutes SP / 120 minutes LP, depending on the tape used; 60/90 minutes SP/LP is standard. This can also depend on the encoding used (see further entries). Files sizes can be up to 1GB per 4 minutes of recording.
Compatibility:
DV file format is widely adopted. Requires Fire Wire (IEEE 1394) port for best transfer.
Users:
Consumer and ‘Prosumer’ film makers, some professionals.
File Systems:
Common Manufacturers:
A consortium of over 60 manufacturers including Sony, Panasonic, JVC, Canon, and Sharp

MiniDV refers to the size of the cassette; as noted above, it can come with any encoding. As a consumer format they generally use DV encoding. DVCAM and HDV cassettes also come in MiniDV size.

MiniDV is the most popular DV cassette, and is used for consumer and semi-professional (‘prosumer’) recordings due to its high quality.

Recognition

These cassettes are the small cassette size, measuring 66 x 48 x 12.2mm. Tape width is ¼”. They carry the MiniDV logo, as seen below:

-Rebecca Nielsen

Preserving born-digital video – what are good practices?

http://www.flickr.com/photos/fensterbme/1990023423/

Interesting to see Killian Escobedo’s post on digital video preservation over at the Smithsonian Archives’ visual archives blog. Our trainee, Emma, is working on questions of these sort at the moment as we start to develop strategies for preserving the vast amount of born-digital video being deposited in our archive collections. While there’s quite a lot of material out there on digitising analogue video, we’ve found a real shortage of guidance on the management of born-digital video collections. With that in mind I’d be really interested in hearing how other folks are dealing with this kind of material. Can you give us any pointers? At the moment we’re particularly interested in learning more about existing practices, good tools, realistic workflows, and preservation-grade standards (for metadata and content – which ones and why?).

So, what kind of digital video do we have? It’s a good question, and one I can’t answer fully for the moment. What I can say is that our collections include digital video deposited on CDs, DVDs, Bluray discs, miniDV and mediumDV cassettes, and hard disks. Much of this material has yet to be captured from its original media so we don’t have that inventory of codecs, wrapper formats, frame rates, metadata, etc. that Killian talks about. This kind of detailed survey work is a next step for us, but one that will have to wait until we have developed a workflow for initial capture (bit-level preservation comes first). I wonder if we’ll see the same diversity of technical characteristics present in the Smithsonian’s materials. It seems likely.

-Susan Thomas