Television signal modification apparatus

Apparatus for encoding video information in horizontal lines of a television signal having a first field and a second field of interlaced horizontal lines, horizontal and vertical timing information, and a dc component, comprising, in combination:

• timing means for sensing horizontal timing information and vertical timing information;
• field detector means for detecting the first field and the second field of horizontal lines in the television signal from the horizontal and vertical timing information;
• counter means for counting horizontal lines in the first field of horizontal lines and for counting horizontal lines in the second field of horizontal lines in response to horizontal timing information;
• code logic means for selecting a first plurality of lines from the counted horizontal lines in the first field;
• complementing means for selecting a second plurality of lines in the second field corresponding by count to the lines not selected as the first plurality of lines;
• and
• video inverter means for inverting video information in the first plurality of horizontal lines in the first field and for inverting video information in the second plurality of lines in the second field, including
• first switch means for selecting the first plurality of lines for inversion in the first field, and
• second switch means for selecting the second plurality of lines for inversion in the second field.

In a television receiver for receiving a television signal having a frame of two fields of interlaced lines, including a chassis, a picture tube, and a plurality of conductors extending between the chassis and the picture tube for transmitting amplified video information from the chassis to the picture tube, apparatus for unscrambling amplified video information in the television signal, comprising, in combination:

• timing means, including means for sensing horizontal timing information;
• counter means for counting horizontal lines in each field of the television signal in response to horizontal timing information;
• code logic means for selecting a first plurality of horizontal lines for inversion in a first field from the counted horizontal lines;
• complementing means including logic means for selecting a second plurality of horizontal lines for inversion in a second field, the second plurality of lines comprising the lines corresponding by count to the lines not selected for inversion in the first field;
• and
• means for inverting the video information of the first plurality of horizontal lines in the first field and of the second plurality of horizontal lines in the second field.

Apparatus for decoding encoded video information in a television signal having a dc component, comprising, in combination:

• timing means, including means for sensing horizontal timing information;
• field detector means for detecting a first field of horizontal lines of video information and a second field of horizontal lines of video information in the television signal;
• counting means for counting horizontal lines of video information in response to horizontal timing information in the first field and in the second field;
• code logic means for selecting horizontal lines for the inversion of video information from the lines counted in the first field;
• complementing means, including logic means responsive to the field detector means, for selecting horizontal lines for the inversion of video information therein from the lines counted in the second field corresponding by count to the lines not selected by the code logic means for inversion in the first field;
• and
• means for inverting the video information of the selected lines in the first and second fields.