REDUNDANCY REDUCTION VIDEO ENCODING WITH CROPPING OF PICTURE EDGES

• US 3,670,096 A
• Filed: 06/15/1970
• Issued: 06/13/1972
• Est. Priority Date: 06/15/1970
• Status: Expired due to Term

• Current Assignee: Frank William Mounts, Gladys Marie Franke, James Charles Candy
• Original Assignee: Frank William Mounts, Gladys Marie Franke, James Charles Candy
• Inventors: Candy, James Charles, Franke, Gladys Marie, Mounts, Frank William
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Martin, John C.
• Application Number:
  US05/046,292
• Time in Patent Office: 729 Days
• Field of Search: 178/6,6.8,DIG.3,15.55R,7.1R,7.2R
• US Class Current: 375/240.14
• CPC Class Codes: H04N 19/152 by measuring the fullness of the transmission buffer
• CPC Class Codes: H04N 19/50 using predictive coding H04N19/61 takes precedence
• CPC Class Codes: H04N 19/503 involving temporal prediction adaptive coding with adaptive selection between spatial and temporal predictive coding H04N19/107; adaptive coding with adaptive selection among a plurality of temporal predictive coding modes H04N19/109
• CPC Class Codes: H04N 7/141 between two video terminals, e.g. videophone telephonic communication systems combined with television receiver for reception of entertainment or information matter H04M11/085

Abstract

In a conditional replenishment video system a coder selects only those samples from an input video signal which represent a significant change in amplitude for their corresponding spatial points within the video frame. A buffer memory in the coder stores the selected samples prior to their being transmitted to a receiving location. In response to an overload signal from the buffer memory, all selection by the coder is stopped for an interval at least as long as one video frame, and a special code word is coupled into the buffer memory. In a plurality of video frames following the cessation of all selecting, only those samples from the center area of the video frame are processed by the coder for transmission to a receiving location. Upon receiving the special code word, the receiver apparatus establishes a constant video amplitude at the edges of the picture outside of the center area. After the above-mentioned plurality of video frames has elapsed, the number of samples processed in each video frame is increased at a rate of one line of picture elements per frame along each edge of the center area of the picture until the entire video frame of samples is again processed by the coder. Visual indication that only the center area of the picture is being processed is given to the party in a visual-telephone system whose activity is causing a cropping of the picture either by means of a display device such as a pilot light or by means of a novel circuit in which the video picture which he sees of the other party is cropped by substantially the same amount as the picture which he is transmitting.

Claims

1. A method of processing samples from a video signal having frame intervals to reduce the redundancy in the transmitted information from said video signal which comprises selecting samples from each frame interval to be transmitted to a receiving location, storing the selected samples so as to provide a reservoir of samples which can be transmitted at a constant bit rate, generating an overload signal when the number of selected samples in storage equals a predetermined number, stopping the selection of all samples in response to said overload signal for a quiescent interval equal to at least one frame interval, and blocking the storage of samples which correspond to spatial points at the edges of a displayEd video frame for a plurality of frame intervals after said quiescent interval.

2. A method of processing samples from a video signal as defined in claim 1 wherein said blocking of the storage of samples for a plurality of frame intervals is removed gradually over a period of several frame intervals by decreasing the number of spatial points at the edges of the displayed video frame whose samples are being blocked from storage.

3. A method of processing samples from a video signal as defined in claim 1 wherein said blocking of the storage of samples is terminated in response to storing less than a second predetermined number of selected samples.

4. Redundancy reduction apparatus for use with a video signal which provides the amplitude for each spatial point within an array of spatial points during each frame interval, said apparatus comprising a source of video signal samples each one of which represents a predetermined spatial point within said array of spatial points, a coder circuit for selecting samples to be transmitted to a receiving location, said coder circuit including a buffer memory which serves to store said selected samples prior to their transmission, said buffer memory having the means to provide an overload signal when it has a predetermined number of samples in storage, a blanking switch means for normally coupling the video signal samples to said coder circuit, said blanking switch means being operative in response to an energizing signal at its control input to block the samples from being coupled to said coder circuit, and means responsive to said overload signal for operating said blanking switch means so as to prohibit the coupling to said coder circuit of those samples which correspond to spatial points at the edges of said array of spatial points.

5. Redundancy reduction apparatus as defined in claim 4 wherein the coder circuit includes a means responsive to said overload signal for totally inhibiting the selection of samples for an interval at least as long as one frame interval.

6. Redundancy reduction apparatus as defined in claim 5 wherein said coder circuit includes a means for coupling a code word to said buffer memory in response to said overload signal to indicate to a remote receiving apparatus that said coder circuit is operating under an overload condition.

7. Redundancy reduction apparatus as defined in claim 4 wherein said coder circuit includes means to operate an indicator circuit during the interval when said blanking switch means is operated.

8. In combination, a source of new video signal samples each one of which represents a video amplitude at a specific spatial point in a displayed video frame, a frame memory means having a stored amplitude sample for each spatial point within the displayed video frame, means for comparing each new sample from said source and its corresponding stored sample in said frame memory means and for developing an energizing signal in response to a significant difference between said new sample and said stored sample, means responsive to said energizing signal for replacing said stored sample with said each new sample in said frame memory means, an address generator synchronized with said source for developing an address word for each new sample which indicates the spatial position of its corresponding new sample, a buffer memory having the means to produce an overload signal when it is storing a predetermined number of samples, means responsive to the replacement of said stored sample for coupling said each new sample and its corresponding address word into said buffer memory, and means responsive to said overload signal for inhibiting the development of said energizing signal for an interval at least as long as the duration of one video frame. 9 The combination as defined in claim 7 wherein said address generator develops a pulse at the start of said displayed video frame, and said means for inhibiting the development of said energizing signal includes a first and second flip-floP each having a set and a cleared state, means for setting said first flip-flop in response to said overload signal and clearing it in response to the pulse from said address generator, means for setting said second flip-flop in response to a cleared state in said first flip-flop and clearing said second flip-flop in response to the pulse from said address generator, and means for developing said energizing signal in response to either of said first or second flip-flops being in its set state.

10. The combination as defined in claim 8 wherein the combination further includes means responsive to inhibiting the development of said energizing signal for developing a blanking waveform having energizing levels at intervals corresponding to predetermined spatial areas in said video frame and having a duration equal to a plurality of video frames, means responsive to the energizing levels in said blanking waveform for blocking said new samples from being coupled to said means for comparing, and means for prohibiting the coupling of said each new sample and its corresponding address word into said buffer memory in response to the energizing levels in said blanking waveform.

11. The combination as defined in claim 10 wherein said buffer memory includes means for generating an empty signal when said buffer memory is storing less than a second predetermined number of samples, and said means for developing said blanking waveform terminates said blanking waveform in response to said empty signal.

12. A conditional replenishment video system for use with video signal samples each one of which represents a video amplitude at a specific spatial point in a video frame, a frame memory means for storing an entire frame of video samples, means for comparing each sample of said video signal samples with a corresponding stored sample in said frame memory means having the same spatial point location in said video frame, means for generating an energizing signal in response to a significant difference in amplitude between said each sample and said stored sample from the frame memory means, an address generator synchronized with said video samples for providing an address digital word for said each sample whose value represents the spatial location of its corresponding video sample, a buffer memory having the means for generating an overload signal when the number of words in storage equals a predetermined number, means responsive to said energizing signal for coupling said each sample and its corresponding address digital word into said buffer memory, means responsive to said overload signal for generating a blanking waveform having energizing levels during intervals that correspond to predetermined spatial points in said video frame, means responsive to said blanking waveform for blocking the video samples from said predetermined spatial points from being coupled to said comparison means, said means for blocking being responsive to said energizing levels for providing a predetermined video signal level to said means for comparing, means for inhibiting the coupling of an amplitude sample and its corresponding address digital word into said buffer memory in response to said blanking waveform, and means responsive to said overload signal for coupling a code word into said buffer memory, said code word providing an indication that said means for blocking is operating in response to said blanking waveform.

13. A conditional replenishment video system as defined in claim 12 wherein said means responsive to said overload signal includes a means for inhibiting the generation of said energizing signal for a predetermined interval equal at least to the duration of one video frame after the generation of said overload signal.

14. A conditional replenishment video system as defined in claim 13 wherein said means for generating a blanking waveform includes a means for indicating the presence of said blanking waveform. 15 A conditional replenishment video receiving apparatus for processing amplitude And address words received from a transmitting location comprising a buffer memory means for storing said amplitude and address words, a frame memory means for storing an entire video frame of amplitude samples, an address generator for providing digital words at its output which indicate by their values specific spatial points within a video frame, said address generator being synchronized with the amplitude samples provided at the output of said frame memory means, means for comparing each digital word developed by said address generator with an address word stored in said buffer memory means and for generating an energizing signal in response to an indication that said each address word and said digital word represent an identical spatial point in the video frame, means responsive to said energizing signal for shifting said address word and an amplitude word out of said buffer memory means, a video display device, blanking switch means for normally coupling amplitude words shifted out of said buffer memory means to said video display device and into said frame memory means, means responsive to said address generator for generating a blanking waveform which has energizing levels at predetermined spatial points within said video frame, and means responsive to the detection of a unique code word at the output of said buffer memory means for coupling said blanking waveform to a control input of said blanking switch, said blanking switch being responsive to said blanking waveform so as to block the amplitude words from being coupled to said video display device and into said frame memory means and instead provide to said video display device and to said frame memory means a constant video amplitude for each of the samples at said predetermined spatial points.

16. Redundancy reduction apparatus for transmitting samples from a locally generated video signal and for processing received samples from a remotely generated video signal, both video signals having time intervals called frame intervals, said apparatus comprising coder means for selecting samples from said locally generated video signal which samples are to be coupled to a remote receiving station, said coder means including a means for generating a blanking waveform having energy levels at intervals corresponding to predetermined spatial points in a frame interval, said blanking waveform being generated by said coder means only in response to an overload condition in said coder means, a blanking switch means responsive to said blanking waveform for blocking samples from the locally generated video signal which correspond to said predetermined spatial points from being coupled into said coder means, a decoder means for assembling the samples from the remotely generated video signal into a continuous stream of video signal amplitude samples;

a video display means for converting video signal amplitude samples into a video frame display, a second blanking switch means for normally coupling the continuous stream of video samples from said decoder means to said video display means, said second blanking switch means having a control input which when energized blocks the video signal samples from said decoder means and provides instead a constant video signal amplitude to said video display means, means for generating a second blanking waveform which has energizing levels at intervals corresponding to predetermined spatial areas in said video frame display, and means responsive to the generation of said blanking waveform in said coder means for gating said second blanking waveform to the control input of said second blanking switch means.

17. Redundancy reduction apparatus for use with a video signal having time intervals called frame intervals, said apparatus comprising a source of samples of said video signal each one of which represents the amplitude of said video signal at a specific point in said frame interval, means for selecting samples to be transmitted to a receiving location, means for coupling the samples from said source to said means for selecting samples, a buffer memory for storing said selected samples prior to their transmission to the receiving location, means for coupling the selected samples into said buffer memory, characterized in that said buffer memory generates an overload signal in response to storing a predetermined number of selected samples, and means responsive to said overload signal for inhibiting the selection of all samples by said selecting means for a duration of time equal at least to a frame interval, wherein said means for coupling the selected samples into said buffer memory includes a means for blocking samples from being coupled into said buffer memory which correspond to predetermined spatial points within each of said frame intervals in response to inhibiting the selection of all samples, and wherein said means for blocking samples includes means for visually indicating that samples are being blocked from said buffer memory.