| 摘要 |
<p>The present invention relates to a method and apparatus for analysing a digital video signal (20) preparatory to the digital compression encoding of the video signal. The signal (20) is applied to an analyser (22) to store samples of the video signal and to derive difference signals representing a number of parameters of the signal. One such parameter is the absolute difference between pixel samples of the signal which are adjacent in a vertical-temporal direction, i.e. the absolute difference between each sample and a sample one frame period later. Other parameters of the video signal are derived from absolute differences between the pixel samples taken over periods of one line, one field and one sample interval. A control signal representing the coding criticality of the input video signal is produced by accumulating the difference signals and combining them as a weighted sum. A low-pass filter in a pre-processor (21) has a bandwidth controlled by the control signal and filters the video signal (20) to remove or limit components which would result in coding artefacts in the signal after compression encoding. The control signal may also be fed to other components in the transmission chain, such as an encoder (23) and statistical multiplexer (24) to provide an early indication of picture criticality.</p> |
