Sony RDR-GX7 - Manual (Page 25)

V-Edge Compensation
In moving images originally created on video, diagonal edges,
depending on the angle, can often appear jagged. In order to
smoothly express these diagonal lines, without jagged effects, the
RDR-GX7 is equipped with original algorithm-based processing
which judges movement at the pixel level, then detects these
edges using an original algorithm. When edges are detected,
information from a number of surrounding pixels in the field is
used to create appropriate pixels to fill and smooth out the edge
for a more precisely even representation.
12-bit 108 MHz Noise Shaped Video D/A Converter
The video D/A converter has a high 12-bit resolution, and
operates at a high sampling frequency of 108 MHz, and is
incorporated onto a single LSI chip. The use of this advanced
D/A converter allows any aliasing noise generated to be shifted
to a higher frequency, enabling the use of an analog low-pass
filter with a gentler sloped cutoff curve and better phase
characteristics to assure superior quality image reproduction.
In the video signal, interlaced luminance signals are
processed at 8-times oversampling to express the image. With
this approach, the D/A converter for playback must have at least
8-bit resolution capability. In the RDR-GX7, however, the D/A
converter has a higher 12-bit resolution to assure processing with
even greater precision.
Accordingly, if sampling is performed at twice the operation
frequency range of the luminance signal, the original waveform,
in theory, can be perfectly reproduced. However, in the process
of sampling, unwanted aliasing noise is generated. In order to
eliminate this, an analog low-pass filter must be employed. But if
the sampling frequency is too low, excess load will be placed
upon the filter, adversely affecting its performance. For this
reason, a high sampling frequency of 108 MHz has been
adopted. This operation frequency represents eight times the
necessary sampling frequency of 13.5 MHz for video signals for
Standard Definition (SD) content with 525 horizontal lines, and
four times the sampling frequency required for Progressive Scan
(PS) content with 525 horizontal lines. Any aliasing noise
accompanying the video signal can be shifted well away into a
higher frequency, where it can be more effectively removed by
an analog filter with a more gently sloped cutoff curve. For a
digital filter, the Super Sub Alias Filter (SSAF) is also employed.
In addition, Noise Shaped Video (NSV) technology is employed
in the D/A converter to shift the noise outside of the operation
frequency bandwidth. As a result, noise inside the operation
bandwidth is greatly reduced, realizing an improvement in the
S/N ratio. These double and triple countermeasures work
synergistically to assure clearer, more accurate reproduction of
video images. These advances assure D/A conversion
performance on par with high-end DVD players for beautifully
superb image quality.
■ DC-coupled Analog Video Circuitry in All Stages
In order to take full advantage of the performance of the 12-bit
108 MHz video encoder, analog video processing circuits with
significantly improved performance have been incorporated into
the design of the RDR-GX7. In order to minimize APL shift and
assure optimum linearity, a dedicated video amplifier has been
adopted. In addition, DC-coupled active LPF and buffer amps
are employed in all stages.
Chapter 4-4
High quality
image & sound
RDR-GX7 Technical Notes
25
The 12-bit 108 MHz Noise Shaped Video DAC
Video
Signal
108 MHz
Sampling at 108 MHz
Super Sub Alias Filter
Including Noise
Analog Filter
Video
Signal Aliasing
Noise
Aliasing
Noise
Aliasing
Noise
Aliasing
Noise
Aliasing
Noise
108 MHz 54 MHz 27 MHz
Sampling at 27 MHz
Analog Filter Loss
108 MHz sampling enables improved noise reduction for better image quality
NSV and SSAF (Super Sub Alias Filter) are trademarks of ANALOG DEVICES, Inc.