Spatial Preprocessing - A Practical Guide to Video and Audio Compression - page 560

What actually happens to the video waveform

Figure 34-11 Slew-rate waveforms.

Figure 34-12 shows the effect of an overshoot in the transitions around the edges. There is
a risk of this happening when the film is processed through a telecine unit that is incor-
rectly calibrated.
The effect is obvious if a small part of the picture is reproduced as a waveform. This
is illustrated in Figure 34-13.
Just enough sharpening should be applied to restore the clean edges.

34.5.3 Edge-Sharpening Damage

Don't turn on any automatic sharpening filters, as this increases edge detail but also intro-
duces more noise artifacts, which are harder to compress effectively. If you are going to do
this at all, then it needs to be done manually and with care.

Original grayscale image Severe edge enhancement

Figure 34-12 Sharpening halos.