Cable TV - Video Inversion

In it's simplest form video inversion is simply taking the video signal and inverting it, and uses the decoder box to re-invert the signal so it's watchable.

The sync and color information remains in it's proper polarity. The data between the Horizontal & Verital Blanking Intervals is what is being inverted which now causes the colorbust signal to become 180 Degrees out of phase with respect to the chroma.

There are different types of video inversion in this day and age in which the video waveform is inverted line-by-line or frame by frame on a pseudo-random basis. Video inversion has also been done by scene changes in the video signal to start the sequence of inversion. The data necessary for the receiver to follow the inversion sequence is sent encoded in one of the 2 blanking intervals, or else can be built into the descrambler in the form of software in an IC.

Some cable companies combing various techniques such as sync suppression and random video inversion making the signal harder to decode for pirates.

Video inversion is most commonly used with synch suppression to strengthen the security of the signal.

Identifying Video Inversion To identify this type of scrambling tune to a channel which appears to have a negative image with only light and dark colors. In most cases audio is in the clear.

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