| 摘要 |
In order to compensate for image distortion introduced into a digitally-controlled raster-scan CRT by the finite video amplifier rise and fall times, the digital video drive waveform is subject to selective pulse stretching to extend where possible the duration of pels which represent critical features of the image. This is achieved by decoding means for examining each pel at least in relation to its two immediate neighbors on either side in order to detect predetermined relationships between the values of the pels, and retiming means for selectively advancing or delaying the transitions between consecutive pels of different value in accordance with the relationships so detected. In one embodiment, suitable for multibit or single bit video, the decoding means comprises means (40, 25) for comparing each pel with its immediate successor, a shift register (26 to 28) for storing the result of each comparison together with the results of a plurality of immediately preceding comparisons, and a logic circuit (30 to 33) connected to the shift register stages, and the retiming means comprises a delay path (41 to 44) for the waveform having an output register (44) and means (34 to 39) responsive to the logic circuit for clocking the output register at a predetermined time in relation to non-selected transitions, earlier than the said predetermined time in relation to transitions selected for advancement, and later than the said predetermined time in relation to transitions selected for delay. |
