Video encoding apparatus

Abstract: In a video encoding apparatus of the invention, a video camera is provided with a moving direction detecting means for detecting movement of the camera in preset moving direction and outputting the detecting signal, a movement information generator is installed for operating the displace­ ment amount of the video camera based on the detecting signal outputted from the moving direction detecting means and calculating the specific position on the memory corres­ ponding to the operated displacement amount of the video camera and outputting the position to a reference signal generator, and plural blocks stored to the specific position on the frame, memory are read based on output from the movement information generator.

Description: The invention relates to a video encoding apparatus for a system in which one of a plurality of video input signals is selected, wherein an interframe difference signal between an inputted video signal and a video signal of one frame before is converted into a quantization encoding signal by a quantization encoder and then outputted, and the quantization encoding signal output is converted into a quantization decoding signal by a quantization decoder and the quantization decoding signal is added to the previous frame and then written back into the frame memory. Fig.1 shows a video encoding apparatus in background art. In Fig.1, numeral 8 designates a plurality of cameras for inputting picture images, and numeral 200 designates a changing device for changing the plural video signals. Numeral 100 designates a video encoding apparatus comprising an A/D converter 1 for converting the inputted video signals in A/D conversion, a pre-processor 40 for performing pre-processing to encode the video signals in digital form, a frame memory 3 for storing the video signal being one frame before the existing frame, a subtractor 6 for estimating difference between output of the pre-processor 40 and output of the frame memory 3, a quantization encoding member 7 for performing quantization encoding of the difference signal between frames, a quantization decoding member 9 for performing the reverse processing to the quantization encoding member 7, and an adder 10. From the video signals outputted from a plurality of cameras 8, only one is selected by the selecting device 200. If the selected signal is inputted to the video encoding apparatus 100, the signal is converted in the A/D conversion by the A/D converter 1 and processed in pre-processing for encoding by the pre-processor 40 and then inputted to the subtractor 6 so as to estimate the difference signal between frames. The difference signal between frames is subjected to quantization encoding in the quantization encoding member 7, and then outputted to the outside and also subjected to the quantization decoding in the quantization decoding member 9. For processing of next frame, the decoded signal is added by the adder 10 to output of the frame memory 3 and then stored in the frame memory 3. An example of practical use of the video encoding apparatus is a teleconferencing system or the like. In a teleconferencing system, a plurality of cameras are often used and signals are suitably changed. Studying the operation when the changing device 200 changes from one camera to another, the output video signals of the changing device 200 become discontinuous just after the changing and the synchronizing signal may significantly fluctuate. As a result, the prior art has problems in that the insignificant difference signal between frames is encoded until synchronization has been completed, and until then the encoding picture image fluctuates. In order to eliminate the fluctuation of synchronous signal, the plural cameras 8 may be synchronously coupled. However, the synchronous coupling of cameras is usually possible only in expensive cameras. An object of the invention is to provide a video encoding apparatus which permits the changing between signals from a plurality of cameras which need not be synchronously coupled. In this apparatus irregularities of the picture image shall be suppressed and made a minimum, and the original picture image shall be restored rapidly. According to the invention, a video encoding apparatus of the type described is characterized in that said video encoding apparatus is provided with a fluctuation detecting means which detects time fluctuations of a synchronous signal contained in the inputted video signal, and the operation of said quantization encoder is inhibited while a fluctuation is detected by the fluctuation detecting means. Preferred embodiments are defined in the dependent claims. In the embodiment, a fluctuation detecting means detects fluctuation of synchronous signal due to changing of input video signals and stops operation of a quantization encoding member so as to prevent the fluctuation of the picture image due to encoding of the significant difference signal between frames. The embodiment will be described specifically. In Fig.2, parts similar to those in Fig.1 are designated by the same reference numerals. Numeral 7 designates a quantization encoding member which can be ON/OFF controlled by external signals, numeral 9 a quantization decoding member which performs the reverse processing to the quantization encoding member 7, numeral 110 a detector which separates the synchronous signal from the inputted video signals and detects the time variation and controls the quantization encoding member 7 and changing means as hereinafter described, numeral 120 a changing device which changes output of the preprocessor 40 and output of the subtractor 6 according to output of the detector 110, and numeral 130 a changing device which changes ON/OFF state of output of the frame memory 3 inputted to the adder 10. The changing devices 120, 130 are set to restore the output of the detector 110 after being lost to the original state with delay corresponding to one frame of the video signal. In this case, the detector 110 constitutes a fluctuation detecting means and the changing device 120 constitutes a signal changing means. Operation of the embodiment will be described. The plural cameras 8 are not synchronously coupled but individually transmit the video signals to the changing device 200. The video signals inputted through the changing device 200 to the video encoding device 100 are converted in A/D conversion by the A/D converter 1, and then processed in pre-processing by the pre-processor 40 and also inputted to the detector 110 so as to perform synchronous signal separation and phase difference detection. The video signal after finishing the pre-processing is converted into the difference signal between frames to that being one frame before the frame memory 3 by the subtractor 6, and the difference signal is inputted to the changing device 120. Both the difference signal between frames and the original video signal are inputted to the changing device 120, but the difference signal between frames is usually outputted from the changing device 120 as shown in Fig.2. The difference signal between frames outputted from the changing device 120 is subjected to the quantization encoding by the quantization encoding member 7, and then outputted to the outside and also subjected to the quantization decoding by the quantization decoding member 9. On the other hand, in the changing device 130, since output of the frame memory 3 is usually outputted without changing, the difference signal between frames subjected to the quantization decoding and outputted by the quantization decoding member 9 is added in the adder 10 to the frame memory output outputted from the changing device 130, and the added output is written to the frame memory 3 and ready to processing of next frame. Studying the operation when the changing device 200 for changing the cameras 8 is changed, since the output video signal becomes discontinuous just after the changing, the detector 110 detects the significant phase shift in synchronous signal. If the detector 110 detects the phase shift, the quantization encoding member 7 stops the encoding of the picture image and prevents the fluctuation of the picture image. At the same time, the changing device 120 for input of the quantization encoder 7 is changed to output the original video signal, and also the changing device 130 for input of the adder 10 is changed so that output of the frame memory 3 is not supplied to the adder 10. If the apparatus finishes redrawing of synchronous signal, output of the detector 110 is lost and the quantization encoding member 7 starts encoding of the original video signal. Then, output of the quantization decoding member 9 is written without changing to the frame memory 3. When encoding of the original video signal corresponding to one frame is finished, the changing devices 120, 130 are reset to the normal state and the original encoding of the difference signal between frames is started. Above-mentioned operation of the embodiment according to the invention is compared with that of Fig.1 as follows: (i) Since time fluctuation of synchronous signal is detected just after changing of the changing device 200 and operation of the quantization encoding member 7 is stopped, irregularity of the picture image due to encoding of the insignificant difference signal between frames is eliminated. (ii) Only just after detecting the finishing of re-drawing of synchronous signal, not the difference signal between frames but the original video signal is encoded. Consequently, restoring to the original picture image is rapid in comparison to the case that the difference signal between frames is used without changing. In the prior art, the picture image becomes irregular at changing the changing device 200 and is restored slowly, whereas in the embodiment of the invention the picture image stands still just after the changing and is restored rapidly.

Claims: Video encoding apparatus for a system in which one of a plurality of video input signals is selected, wherein an interframe difference signal between an inputted video signal and a video signal of one frame before is converted into a quantization encoding signal by a quantization encoder (7) and then outputted, and the quantization encoding signal output is converted into a quantization decoding signal by a quantization decoder (9) and the quantization decoding signal is added to the previous frame and then written back into the frame memory (3), characterized in that said video encoding apparatus is provided with a fluctuation detecting means (110) which detects time fluctuations of a synchronous signal contained in the inputted video signal, and the operation of said quantization encoder (7) is inhibited while a fluctuation is detected by the fluctuation detecting means (110). Video encoding apparatus as claimed in claim 1, characterized by a signal changing means (120, 130) operated by an output of the fluctuation detecting means (100), to change the input to the quantization encoder (7) from the interframe difference signal to the input video signal, and to permit writing of the unchanged output of the quantization decoder (9) into the frame memory (3). Video encoding apparatus as claimed in claim 2, characterized in that said signal changing means (120, 130) changes back to the non-operated position at a delay corresponding to one frame of the input video signal after the state of the fluctuation is no longer detected.

Inventors: ASANO KENICHI, KIKUCHI HIROAKI, KUBO TSUTOMU, SUZUKI MITSUYOSHI, ASANO, KENICHI, KIKUCHI, HIROAKI, KUBO, TSUTOMU, SUZUKI, MITSUYOSHI
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1986
Main classification: H04N7
IPC codes: H04N5, H04N7, G06T9