New Technique; Laservision With Digital Sound Disc (Ldd) - Pioneer tuning fork Service Manual

LaserVision with Digital Sound Disc (LDD)

As discussed on the page 74, Vol. 7, NTSC L D D discs have
digital sound information in addition to the conventional
analog picture and sound information.
The NTSC L D D system allocates a frequency space to
digital sound signal which has a frequency band of 0-2MHz
as seen in Fig. l a and 2a.
The level of the digital sound signal is a little higher than
the analog sound carriers. If the level is too high, the digital
signal will interfere video signal, and if it is t o o low, bit
error rate will increase and random noise will be generated.
NTSC LaserVision standard
dB
A i A 2
a. NTSC
Fig. 1 Frequency Spectra of NTSC and PAL LaserVision Signal
Audio signals
Digital
Analog
dB
a. NTSC

New Technique

Sync
freq. MHz
Video signals
freq. MHz
Fig. 2 Inserting Digital Signal into LaserVision Signal
Unfortunately, in the frequency spectrum of P A L LV sys­
tem, there is no r o o m for the digital sound because the
range of 0-2MHz has already been occupied by two audio
carriers of 684kHz and 1,066kHz as seen in Fig. l b . It is
necessary to remove the two analog sound carriers and the
second lower sideband of the video carrier to insert the dig­
ital sound signal in the spectrum. The compatibility be­
tween the conventional P A L LV disc and P A L L D D disc
will be lost if the carriers are removed. P A L L D D discs
are not being marketed because of this incompatibility.
PAL LaserVision standard
dB Audio
signals
A1 A2
b. PAL
Digital audio
dB
signal
b. PAL
Sync
freq. MHz
freq. MHz
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