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'Digital-8 (or D8)' is a consumer digital videotape format developed by Sony, and introduced in 1999.
The Digital8 format is the combination of the venerable Hi8 tape transport with the DV codec. Digital8 equipment uses the same videocassette-media as analog Hi8 equipment, but differs in that the audio/video signal is encoded digitally (using the industry-standard DV codec.) Since Digital8 uses the DV codec, it has identical audio and video specifications.
To facilitate digital-recording on existing 8 mm videocassettes, the tape-media is moved linearly past the recording-heads at higher speed, while the video head-drum spins 2.5x faster. For both NTSC and PAL Digital8 equipment, a standard-length cassette will store 60 minutes (at Standard Play.) Current Digital8 equipment can also record in Long Play (LP) mode, which increases recording-time from 60minutes to 90minutes. A few vendors sell long-duration tapes, with an SP recording-time of 90 minutes (or 125 minutes in LP.)
Digital8 (SP) recordings can be made on standard-grade Video8 cassettes, but this practice is discouraged. Hi8 metal-particle cassettes are the recommended type for Digital8 recording.
MiniDV/DVC vs. Digital8
Contrary to popular perception, the Digital8 format is not technically inferior to miniDV -- both are identical at the bitstream-level. From a user standpoint, Digital8 is DV (or rather, equivalent to and compatible with consumer miniDV.) At an application level (for example, in a 1394/Firewire link), a Digital8 camcorder appears and behaves exactly like a DV camcorder.
Digital8 and miniDV use different, non-interchangeable cassette media, with Digital8 cassettes being the physically larger of the two. The two formats may also use different media-formulations: Digital8 can use metal-particle or metal-evaporated media, while miniDV is based solely on metal-evaporated media. The standard (SP) recording-time for both formats, on standard length media, is 60 minutes. Special high-capacity cassettes are also available for both formats which can extend these figures, and both offer Long Play modes which extend recording times by 50% (not 100% as for video8 Long Play).
Market segment
While analog Hi8 video enjoyed widespread use by amateur home-video, current affairs TV programs, and some professional news organizations, Digital8 seems to remain strictly a consumer (amateur) product. This is likely a reflection of Sony's design and market objectives for Digital8 format: to serve as a low-cost upgrade path for current customers (from analog 8 mm), by leveraging existing manufacturing infrastructure of 8 mm video equipment. Furthermore, Digital8 was released some time after miniDV, giving the rival DV-format a lead in the professional market. (Little or no equipment has been produced for the professional market, although there are no technical barriers opposing its development.)
In the early years after Digital8's introduction, Sony sold a product-line with coverage from entry-level to high-end consumer. The best of the consumer Digital8 product-line was a small number of megapixel camcorders, sold during the years 2001-2003. The Sony DCR-TRV730/828/830 (and the later DCR-TRV740/840), were the only Digital8 camcorders to be built with a high-quality "megapixel" CCD. All megapixel camcorders featured a CCD sensor with an active pixel-count of ~670K, ranking them competitive with similarly equipped single-CCD miniDV camcorders.
But since that time, Sony has withdrawn this capability from its Digital8 product-line, preferring to promote high-density imagers in its miniDV and DVD camcorders. Furthermore, the number of models in Sony's Digital8 product-line has shrunk, raising questions about the format's future.
As of 2005, Digital8 product-line caters purely to the entry-level consumer. This is most likely because the larger, bulkier Digital8 cassette is perceived as an inferior technology, even though the Digital8 and DV formats offer indistinguishable A/V performance. Sony, the format's original backer, is the only company still producing Digital8 equipment. Hitachi marketed a few Digital8 camcorders for a while but no longer does so.
Analog recordings
Digital8 equipment cannot record in analog Video8/Hi8 format, but some equipment offers playback-compatibility with 8 mm analog-recordings. Even so, there are limitations: audio-playback is limited to the analog soundtrack -- if present, digital (PCM) sound is inaccessible. Most Digital8 camcorders with analog-playback also simultaneously digitize the analog-footage into the DV format, sending the converted material through the camcorder's FireWire interface. This facilitates easy, one-step uploading of analog 8 mm recordings to a Firewire-equipped PC/Mac. As Digital8 offers audio/video performance equal to DV, little if any of the original recording's fidelity is lost due to the conversion process (although some purists contend high-end Hi8-playback equipment looped through a DV-encoder produces better results.)
When Sony introduced Digital8 in the late 1990s, it was positioned as a direct-upgrade for the 8 mm video-market. Consequently, analog 8 mm-playback was a mandatory feature for its intended market, and available on all introductory Digital8 camcorders. In later years, as market evolution relegated Digital8 to the low-end camcorder market, such a feature was no longer crucial. Hence, analog-playback is now limited to select Digital8 models.
See also
"Digital8"