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This section describes the recording format, heads configu-
ration and signal processing.
A-1. Outline
Sony DNWseries are 1/2-inch component digital VTRs
using a new "Betacam SX" format.
In the Betacam SX format, "MPEG2 4:2:2 Profile @Main
Level" is used as a compression system.
Interframe compression technology is first used as VTR
format. The data rate is compressed to approximately 1/10
by this technology. The compressed data is then recorded
(Note1
on tape
.
By compressing of the data rate, the S cassette makes
continuous recording of 62 minutes possible, and the L
cassette makes continuous recording of 194 minutes
possible.
Moreover, the data can be recorded on not only the cassette
for the Betacam SX but also the metal particle tape for the
conventional Betacam SP by Betacam SX format.
This unit enables the high-reliability playback without
using a high-precision tracking by the head configuration
based on Multiple Tracing technology.
In this unit, the analog tape (oxide and metal particle)
recorded based on the Betacam and Betacam SP formats
can also be played back. Therefore, current analog Beta-
cam recorded tapes can also be used directly.
Note 1: The audio data is recorded by non-compression.
Multiple Tracing Technology
In the Multiple Tracing technology, the non-tracking technol-
ogy used for a digital audio tape recorder is applied for VTR.
This technology requires no high-precision tracking during
recording as well as playback.
For the playback at variable speed, it was necessary changing
the drum rotation relative the tape speed or using the dynam-
ic tracking (DT) heads for precision tracking in the past.
DNW-A75/A75P
Appendix A
Outline of Format
In this multiple tracing technology, two playback heads are
provided for one recorded track. If one playback head
missed the recorded track, the another playback head
makes up the complete playback signal.
This technology enables the variable-speed (JOG) playback
(_1 to +2 times the normal speed) without using the
conventional dynamic tracking (DT) head.
A-2. Recording Format
Footprint
Fig. A-2-1 shows the footprint in the 525/60 system (the
top of figure) and the 625/50 system (the bottom of figure) .
This figure shows the tape pattern of a Betacam SX at
right, and the footprint of a Betacam SP at left, respective-
ly.
Footprint of Helical Track
In the Betacam SX format, two-frame (1 GOP*) video
data, system data and four-channel audio data is recorded
on ten (525/60 system) or twelve (625/50 system) helical
tracks.
*GOP: Group of Pictures
This unit records two helical tracks in pairs. Therefore, the
drum rotation is approximately 75 per second (common in
525/60 and 625/50 systems).
In the playback of the Betacam or Betacam SP format, the
number of drum rotations is approximately 30 per second
(525/60) or 25 per second (625/50)
Moreover, the tape speed of the Betacam SX format is
lower than that of the Betacam/Betacam SP format by
approximately half.
This unit detects whether the tape to be played back is
based on the Betacam SX format or Betacam/Betacam SP
format by the initial signal of playback, and as a result, the
tape is played back by the proper drum rotation and tape
speed.
Note 2 : When using Betacam and Betacam SP formats,
only simple viewing is possible for tapes recorded
in different system.
(Note2
.
A-1
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