Introduction
MiniDV is a digital video cassette format that utilizes the DV encoding standard. The first MiniDV camcorder was released in 1996 and was used in consumer, industrial, and educational sectors. MiniDV has the same tape width (1/4") and compression as standard DVC, however the tape is housed in a smaller cassette. MiniDV was more popular among consumers at the time and became the most widely used DV cassette format. Some MiniDV cassettes incorporated memory in cassette (MIC) technology to store additional data such as camera settings, dates and times of recordings and a list of contents.
Physical Characteristics
| Tape width | ¼ inch (6.35mm) |
|---|---|
| Tape composition | Metal evaporate (ME) |
| Cassette dimensions | 2 9/16" x 1 7/8" x 7/16" |
| Container dimensions | 2 7/8" x 2" x 5/8" |
| Identifying features | Sony MiniDV cassettes are usually labeled in the lower left hand corner Panasonic MiniDV cassettes are usually labeled with a sticker on the right side |
| Common manufacturers/brands | Sony, Panasonic, JVC |
| Playback |
|
Technical Characteristics
| Record time | Standard play: 60 - 80 minutes Long play: 90 - 120 minutes |
|---|---|
| Record/playback speed | Standard play mode: 18.81 mm/sec |
| Track pitch | Standard play: 10 microns Long play: 6.7 microns |
| Track width | Standard play: 10 microns Long play: 6.7 microns |
| Bitrate | 25 Mbit/s |
| Bit depth | 8 bit |
| Colour sampling | PAL: 4:2:0 NTSC: 4:1:1 |
| Resolution | PAL: 720x576 |
| Compression | 5:1 DVC-format DCT compression (intra-frame) |
Storage
| Storage environment: temperature | Ideal: 40–54°F (4.5–12°C) Acceptable: 55–60°F (13–15.5°C) |
|---|---|
| Storage environment: humidity | 30–50% RH |
| Container | MiniDV containers should pass the Photographic Activity Test (PAT) as specified ISO Standard 18916:2007
Containers are acceptable if they:
Unacceptable containers must be replaced with clean, inert containers. |
| Orientation of tape in storage | Vertical on its end (like books) |
Risk assessment
Digital video material stored on magnetic videotape is considered to be at high-risk of loss or degradation.
Polyester base film used in videotape is considered very stable.
Other components of the videotape, including the binder, are considerably less stable and are more likely to be the cause of degradation.
Format obsolesce, including lack of well-functioning playback equipment poses an equal or even greater risk than degradation, even with higher quality formats such as Digital Betacam
Digital video material stored on magnetic tape should be appraised or re-appraised to determine the nature and signficance of video elements contained on the tape and whether the video elements have sufficient archival value to justify reformatting and long-term preservation as digital video files.
Types of damage and deterioration
| Binder deterioration | |
|---|---|
| Description | Commonly known as "sticky shed syndrome." Affected records will have a visible gummy or powdery residue on the surface of the tape. This can damage both the recorded material and playback equipment. Back-coated tapes are most affected by this type of deterioration. |
| Cause | Polyester urethane is prone to moisture absorption which can cause the molecular structure of the binder to break down. This process is accelerated by high temperature and high humidity. |
| Remedy | Environmental conditioning: Moving the tape to a controlled storage environment (40°C / 20 to 25% Relative Humidity) may reverse the affects of hydrolysis over time. Baking: Holding the tape at an elevated temperature (45°C to 55°C) for a brief period of time (up to 36 hours) can temporarily remove moisture and allow normal playback for a period of one to two weeks. Tapes should not be rewound before baking. |
| Drop-out | |
| Description | A brief signal loss caused by a tape head clog, missing magnetic oxide particles, tape defect, or debris on the tape or machine. These factors can reduce head-to-tape spacing and result in the appearance of white spots or streaks on playback. Multiple drop-outs per frame will result in a snowy appearance. |
| Cause | Tapes kept in dusty conditions will accumulate particulate matter, increasing the risk of drop-out. |
| Remedy | Flaking/missing magnetic oxide particles are an indication of tape deterioration. This type of drop-out cannot be corrected physically. |
| Mould | |
| Description | Active mould is generally moist while dormant mould is dry and dusty. Mould growths may be white, black, brown or mustard-coloured and usually have a pattered, fuzzy, or thread-like appearance. Mould can cause permanent damage to tapes over time if not removed. Fungus and mould is also a significant health hazard and affected materials should be handled using gloves and masks. |
| Cause | Storing tapes at high temperature and relative humidity levels can facilitate the growth of mould. |
| Remedy | Mouldy tapes should be isolated from unaffected materials to prevent cross contamination. Store tapes at a temperature of 24°C in an environment with effective air circulation and less than 50% Relative Humidity. Loose mold can be vacuumed from the tape pack and then the tape should be treated with an appropriate fungicide. |
| Stretching and breaking | |
| Description | The elongation of parts of the tape, across the full width of the tape or -most likely- on one or the other side of the tape The separation of tape into two or more pieces. |
| Cause | usually results from either improper wind or from faulty equipment. May cause long-edge or curvature problems, and distort the signal, but the data can generally be retrieved from an analog tape, usually with a decrease in signal quality." Improper handling or use of playback equipment. |
| Remedy | |
| Accidental recording | |
| Description | Camera operators can accidentally record over pre-existing footage |
| Cause | Tape is set to "record mode" when it is inserted into camera or deck |
| Remedy | Ensure tape is set to "safe mode" before inserting into camera or deck |
Further Reading
Visit the /wiki/spaces/ALC/overview for further reading on /wiki/spaces/ALC/pages/1891631115.
Sources
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