| 摘要 |
<p>1506530 Video signal encoding; digital transmission ROBERT BOSCH GmbH 3 Nov 1975 [15 Nov 1974] 45665/75 Headings H4F and H4P Delta-encoded video signals are fed to a quantizer which is changed for a predetermined time from a first quantization characteristic to a second when the video signal exceeds a preset threshold level. The signal exceeds this level when it represents a substantial change in contrast, e.g. the edge of an object in the scanned field. In order to reduce the noise that would otherwise appear in the picture as a consequence of jitter from one characteristic to the other when noise accompanying the video signal causes the signal to jitter about the threshold level, the characteristics have a common switching level, equal to the threshold level, at which the quantizer output changes from a first value to a second value, the first values and the second values respectively being the same for both characteristics. The output is therefore the same for a signal level closely above, or alternatively closely below, the threshold level irrespective of which characteristic is operative.</p> |
