Complete Communications Engineering

Basic Video Sharpening with Controlled Granularity and Noise Coring mitigates the effects of boosting high frequency noise during video sharpening. Video Sharpening is essential for output video processing devices that enhance the subjective video quality.

The basic approach for video sharpening is to boost middle and high frequencies of the progressive image in the vertical and horizontal directions. The middle frequencies are boosted more than high frequencies to have a high level of perceptual quality.

Basic Video Sharpening with Controlled Granularity
Fig. 1 Basic Video Sharpening with Controlled Granularity

To smoothly control the sharpening process, the high frequency part of the filter is extracted to a separate path, multiplied by the sharpening control coefficient and added back to the delayed (by FIR delay) input signal.

Since video sharpening is based on boosting the high frequencies, the typical issue with sharpening is increasing the high frequency noise. To mitigate noise boosting, noise coring for the high frequency path is applied.

As illustrated in Figure 1, the noise coring block is a nonlinear block that essentially removes fine detail information, which adds noise but does not contribute significantly to the image. The transfer function is shown in Fig.3. The output signal can be described by the equation:


where Rc – is the coring range parameter.

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