Audio Engineering

Video Synchronization 821

Picture

modulation

Colour modulation

Line sync pulse

Line

blanking

Peak video

modulation

700 mV (PAL)

0V (black level)

300 mV (PAL)

Burst

Figure 28.7 : Color television signal.

relationship with the incoming signal. For these reasons the local oscillator must be phase
locked and for this to happen the oscillator must obviously be fed a reference signal on
a regular and frequent basis. This requirement is fulfi lled by the color burst waveform,
which is shown in the composite color television signal displayed in Figure 28.7.

Low-pass filter

Low-pass filter

Low-pass filter

Band-pass filter

Composite

video

Subcarrier

oscillator

Delay

90 Degrees

phase-shift

B – Y

R – Y

Y

Phase lock



Figure 28.6 : NTSC color decoder.