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The quality of videotape formats is usually measured in
lines of "horizontal resolution." Horizontal resolution is a
term measuring the clarity in a single scan line of a
television image. The higher the number, the better the
quality and detail.
However, "horizontal resolution" is a misleading term. The
lines that run horizontally across an NTSC television screen
are set, fixed, at a solid 525 lines. The lines that run
vertically up and down a NTSC screen are relative. But, the
vertical-running lines are creating a pattern across the
horizontal plane of the screen, so they are called "horizontal
lines" even though they run vertically. This makes it very
confusing to explain vertical and horizontal resolution.
The vertical line resolution stays
fixed all the time. The
newest JVC to the oldest Sanyo all had the same 525 lines.
But, the horizontal resolution can increase a great deal as TV
technology improves. Standard analog broadcast television in
the United States has about 330 lines of horizontal
resolution. In comparison, a DVD has about 480 lines of
horizontal resolution. DV, DVCPRO, DVCAM (1996 - 1998)
DV is a format
backed by manufacturers such as
Sony, Philips, Hitachi, Matsushita
(Panasonic) and others.
As the first
digital video recording system for consumers, Mini DV
represents a significant advance in video quality over
conventional analog recording, with an unprecedented 500-line
horizontal resolution-100 lines greater than Hi8 or S-VHS
recording. The DV
format has two cassette sizes: Standard/
Full Size (125mm by 78mm by 14.6mm) and
Mini DV (66mm by 48mm by 12.2mm). The new DV
VCRs will accept both, but the current crop of camcorders
accept only the Mini DV.
DVCPRO
is a professional variant of DV by Panasonic. The only
major difference is doubled tape speed, which is needed for
better drop-out tolerance and general recording robustness. It
is also capable of 4x normal speed playback. This doesn't mean
ordinary Fast Forward with picture, but rather, accelerated
transfer of all of the information, for example, into a
non-linear editing system.
DVCam is Sony's variation of the theme, sitting
somewhere between DV and DVCPRO. Tape speed and track width
have been increased, but not as much as for DVCPRO. Furthermore, it uses the same metal evaporated tape as DV,
while DVCPRO uses metal particle tape.
DVCam
DVCAM is the exact same size as
DV and is backwards compatible with DV. The format has the
exact same resolution as DV, however, the "track pitch" is
wider on DVCAM. This means that the tape physically spins
around the spools a bit faster than a DV tape and therefore
the video information is recorded over a longer span of tape.
Being more broadly recorded onto the tape means the image is
less prone to dropouts or loss in quality. To be more
specific, DV uses 10 micron tracks in SP recording mode and
DVCAM uses 15 microns.
DV and DVCAM tapes and VTRs are widely compatible. For
example, it is possible to record professional DVCAM signals
onto consumer DV tape. It is also possible to play back a DV
recording on a professional DVCAM machine. In a pinch, it is
possible to use consumer media in professional DVCAM hardware.
DIGITAL FORMAT
COMPARISON TABLE
|
Format |
BIT
RATE |
SIGNAL
SAMPLING |
COMPRESSION RATIO |
TAPE
WIDTH |
| DVCPRO |
25
Mb/sec |
4:1:1 |
5:1 |
1/4" |
| DVCPRO
50 |
50
Mb/sec |
4:2:2 |
3.3:1 |
1/4" |
| DV
& Mini DV |
25
Mb/sec |
4:1:1 |
5:1 |
1/4" |
| DVCAM |
25
Mb/sec |
4:1:1 |
5:1 |
1/4" |
| DIGITAL-S |
50
Mb/sec |
4:2:2 |
3.3:1 |
1/2" |
| BETACAM
SX |
18
Mb/sec |
MPEG-2 Inter-Frame |
10:1 |
1/2" |
| DIGITAL
BETACAM |
90
Mb/sec |
4:2:2 |
2:1 |
1/2" |
FORMAT
COMPATIBILITY TABLE
|
Format |
Format
Compatibility |
| DVCPRO |
Record DVCPRO, Playback of DV and
DVCAM |
| DV
& Mini DV |
Record DV, Can Be Played Back on DV, DVCAM &
DVCPRO |
| DVCAM |
Record DVCAM, Playback of DV, Played Back on
DVCPRO |
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