VEIL modulation is a method of “subliminal” encoding of data in a video image that is similar to a watermark. The encoding consists of alternately proportionately raised and lowered luminance on selected horizontal scan lines. The encoding can be detected using a notch filter centered at half the...http://www.google.com.tw/patents/US7167209?utm_source=gb-gplus-share專利 US7167209 - Methods for encoding data in an analog video signal such that it survives resolution conversion
