ES DVD Players 2005, Version 4.0 Page 20
samples. 8X oversampling inserts seven additional samples. And 16X
oversampling inserts fifteen additional samples.
The benefit is this: in the process of generating additional samples,
oversampling shifts the aliasing noise up in frequency, opening up substantial
room between the video signal and the noise. With more room, we can relax the
design of the analog filter, which can be far milder in slope, and far more effective
at optimizing both the picture detail and the picture clarity.
27 MHｚ-Sampling
5427 108 216
Noise Noise Noise Noise Noise Noise Noise Noise
Video
Signal
Analog-Filter
54 MHｚ-Sampling
5427 108 216
Noise Noise Noise Noise
Video
Signal
108 MHｚ-Sampling
5427 108 216
Noise Noise
Video
Signal
216 MHｚ-Sampling
5427 108 216
Noise
Video
Signal
These diagrams show interlaced video and the need for oversampling.
At 27 MHz sampling (top), the design of the filter (red curve) must be
extremely steep to avoid cutting into the video detail (blue) or passing
some of the noise (pink). At 54 MHz (second from top), the filter is
somewhat better. And at 108 MHz (third from top), the filter becomes
better still. Oversampling at 216 MHz (bottom) leads to a far more
effective analog low-pass filter. This enables the Sony® ES Series DVD
players to deliver all the picture detail, without degrading the clarity of
the image with noise.
Oversampling, which is useful for interlaced video, becomes indispensable
for progressive scanning video. Because progressive scanning outputs twice as
many horizontal lines per second, progressive playback effectively doubles
channel bandwidth to 13.5 MHz and doubles sampling frequency to 27 MHz.
Players need a minimum of 27 MHz sampling in order to output a progressive
signal.