Video signal coding by video signal polarity reversal on the basis of brightness level comparison

• US 4,340,906 A
• Filed: 05/14/1980
• Issued: 07/20/1982
• Est. Priority Date: 05/14/1980
• Status: Expired due to Term

• Current Assignee: Tv/com Technololgies, Inc.
• Original Assignee: Oak Industries, Inc. (Corning Incorporated)
• Inventors: Stubbs, Graham S., Jirka, Howard F., den Toonder, Pieter, Fondse, Pieter J., Seltenrijch, Johannes C.
• Primary Examiner(s): BUCZINSKI, STEPHEN C
• Application Number:
  US06/149,708
• Time in Patent Office: 797 Days
• Field of Search: 358/120, 358/123, 358/124
• US Class Current: 380/222
• CPC Class Codes: H04N 7/167 Systems rendering the television signal unintelligible and subsequently intelligible

Abstract

A method and means for coding and decoding video signals by repetitive video signal polarity reversal includes the steps of comparing the brightness level of a predetermined time period of the video signal with the brightness level of the video signal over the previous predetermined time period. The polarity of the video signal is inverted or reversed if the difference in brightness level between successive predetermined time periods exceeds a given value.

Claims

1. A method of coding video signals by repetitive alteration of the coding mode including the steps of:

(a) detecting a change in the picture scene carried by the video signal by comparing the brightness level of a predetermined time period of the video signal which time period includes a video signal field with the brightness level of the video signal over the succeeding predetermined time period, the brightness level being determined by comparing the instantaneous brightness level at successive subdivisions of said time period, each less than a single horizontal line, with an average brightness level,

(b) altering the coding mode of the video signal if the difference in brightness level between successive predetermined time periods exceeds a given value,

(c) and preventing such alteration of the coding mode except only between frames of the video signal.

2. The method of claim 1 further characterized in that within each video signal field there are multiple samples of instantaneous brightness level in less than all horizontal lines.

3. Apparatus for coding video signals by repetitive alteration of the coding mode including:

(a) means for detecting a change in the picture scene carried by the video signal including means for providing a signal representing the brightness level of a video signal during a predetermined time period of said signal, which time period includes a video field, including means for comparing the instantaneous brightness level at successive subdivisions of said time period, each less than a single horizontal line of the video signal, with an average brightness level,

(b) means for comparing the representative signal of one time period with the representative signal of an adjacent time period,

(c) means for causing video signal coding mode alteration when the difference between successive representative signals exceeds a predetermined value

(d) and means for permitting video signal coding mode alteration only during a vertical interval of the video signal.

4. The apparatus of claim 3 further characterized by and including means for providing multiple samples of the instantaneous brightness level of the video signal during less than all of the horizontal lines in each field.

5. The apparatus of claim 3 further characterized by and including time delay means preventing video signal coding mode alteration unless a predetermined time period has elapsed since the last video signal coding mode alteration.

6. The apparatus of claim 3 further characterized by and including means for suppressing the synchronizing information during the horizontal and vertical blanking intervals, and means for inserting digital sound data and control signal data in said suppressed blanking intervals.

7. The apparatus of claim 3 further characterized in that said coding mode alteration includes video signal polarity reversal.

8. Means for decoding a video signal coded by video signal coding mode alteration in response to a detected change in the picture scene carried by the video signal by determining the difference in brightness level between successive predetermined video signal time periods exceeding a given value which time periods include a video signal field, with the brightness level being determined by comparing the instantaneous brightness level at successive subdivisions of said time period, each less than a single horizontal line, with an average brightness level, with the alteration in coding mode being permitted only during a vertical interval of the video signal and in which the synchronizing information during the video horizontal blanking intervals has been suppressed and in which digital sound data and clock data have been inserted in horizontal blanking intervals, including:

(a) means for detecting a change in coding mode, and means for changing the decoding mode in response to detection of a change in said coding mode,

(b) sync pulse generating means,

(c) means for detecting the clock data and applying it to control the sync pulse generating means to provide synchronizing pulses for horizontally referencing a video signal,

(d) means for reconstituting a usable audio signal from said digital sound data,

(e) and means for combining the reconstituted audio signal, the horizontal sync pulses and the video signal to provide a television signal usable in a conventional television receiver.

9. The apparatus of claim 8 further characterized in that sync information during the vertical blanking intervals has been suppressed and vertical reference signal data has been inserted therein, said apparatus including means for detecting the vertical reference signal data and applying it to the sync pulse generating means to provide synchronizing pulses for vertically referencing a video signal.

10. Means for decoding a video signal coded by the repetitive alteration of the coding mode in response to a detected change in the picture scene carried by the video signal by determining the difference in brightness level between successive predetermined video signal time periods exceeding a given value, which time periods include a video signal field, with the brightness level being determined by comparing the instantaneous brightness level at successive subdivisions of said time period, each less than a horizontal line, with an average brightness level, and with the alteration in coding mode being permitted only during a vertical interval of the video signal, including means for detecting a change in coding mode, and means for changing the decoding mode in response to detection of a change of said coding mode.