JPH01166622A - Inter-frame prediction coding/decoding device - Google Patents

Abstract

PURPOSE:To minimize the deterioration of the quality of a picture for a TV conference or the like in low bit subject to changeover of an input signal by suppressing the production of a pseudo signal of a vertical synchronizing signal once at maximum when the input signal is changed over. CONSTITUTION:When a signal Sin inputted to a differential coding section 1 is switched, a vertical synchronizing signal detector of a detector 2 detects the input switching to drive a selector 31C of a signal selector 3C at the coder side. Then a prescribed prediction signal is sent as the input signal Sin after the changeover, the output of the signal selector 3C is used as a prediction value in the differential coding section 1, where differential coding is applied and its coded output Dout is outputted to a transmission line 4 together with a detection signal (d) of the detector 2. A pseudo synchronizing signal is generated only once after the frame being the result of the changeover of the input signal Sin at the coding side at the decoder side being the reception side of the transmission line 4, then one normal vertical synchronizing signal per one frame is outputted afterward.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an inter-frame differential encoding/decoding device that uses a frame memory to calculate the difference in a moving image TV signal, encodes it at a low bit rate, and transmits it, when the input TV signal is switched. In order to prevent the amount of information generated from both TV images that are differentially encoded from increasing and the vertical synchronization signal to become duplicated, which deteriorates the quality of the A, the input signal's vertical synchronization signal is de-synchronized. A detector to detect and an output Xo of the frame memory according to the output of the detector.
a signal selector that selects a zero code for one frame and then selects a signal delayed by a certain period of time from the output of the differential encoder, and uses the output of the signal selector as a prediction signal and an input signal. The code Dout obtained by taking the difference and quantizing the code Dout and the output d of the detector are sent to the decoding side via a transmission path, and on the decoding side, the signal selector on the decoding side is operated by the output d of the detector. To decode the incoming code Dout'
It is structured as follows.

[Industrial application field]

The present invention relates to an interframe differential encoding/decoding apparatus that uses a frame memory to calculate the difference between frames of a moving image TV signal, performs low bit rate encoding, and transmits the encoded signal.

As an inter-frame differential encoding/decoding device, it is possible to suppress the amount of information generated when the TV signal of the moving image input to the device is switched to another TV signal, and to synchronize vertically between both differentially encoded TV images. It is desirable that the image quality is less likely to deteriorate due to signal duplication.

[Conventional technology]

TV signals of moving images at low bit rate (6 to 0.7 Mb)
Conventionally, an encoder using the interframe differential encoding/decoding method that encodes and transmits the video signal (S) has a configuration as shown in FIG. The difference between the signal for one frame and the output signal from the frame memory 14A that stores the signal of the previous frame is taken by a subtractor 11A, and the output of the subtractor 11A is converted to a quantizer (Q). 12A, and when the TV image source input to the differential encoder 1 is switched to another TV signal, the 2 signals before and after the switching are
Since there is no correlation between the frames, a lot of information is generated in the output of the subtractor 11A that represents the difference between the two frames, and a buffer memory is used to temporarily store the output code of the quantizer 12A.
8 sends a stop signal 5TOP to the quantizer 12A, stops the encoding operation of the quantizer (Q) 12A, and outputs the quantized output e.
becomes zero, and as a result frame memory (FM) 14
The change in the output Xo of A becomes zero, reducing the output of the subtractor 11A and the generation of information from the quantizer 12A.

[Problem that the invention seeks to solve]

As mentioned above, when the input image source of the differential encoder IA is switched to another image, the differential encoder 18 of the conventional inter-frame differential encoding method calculates the difference between the two frames before and after the switching. A lot of information is generated at the output of the subtractor 11A representing One frame worth of signals near the vertical synchronization signal of the TV signal before switching stored in 14A will be used. Therefore, the difference unit 11A uses the same data stored in the frame memory 14A one frame ago, and as a result, the quantizer 1
As shown in Figure 3, the encoded signal of the output of 2A is such that the vertical synchronization signal after frame 3' after switching is divided into the vertical synchronization signal F(2) and the pseudo vertical synchronization signal F(1) per frame.
), and when viewing the encoded output on a video monitor, there is a problem in that the image quality deteriorates significantly.

[Means for solving problems]

This problem occurs when the input signal of the differential encoder 1 is switched, and the vertical synchronization signal of the input signal deviates from a constant period, that is, the synchronization is detected. Based on the detection output d, it is determined that the input signal has been switched. Then, the prediction signal output Xo from the frame memory of the differential encoder 1 is cut off, zero code is selected for only one frame after switching, and after that, the prediction signal in the frame in which the output of the differential encoder 1 is delayed by a certain period of time is The problem is solved by the configuration of the present invention, which includes a signal selector for selecting.

In the principle diagram of FIG. 1 showing the configuration of the interframe predictive coding/decoding device of the present invention, 1 is an output signal of a frame memory that stores a signal for one frame of an input TV signal and a signal one frame before. 2 is the synchronization of the vertical synchronization signal of the input signal of the i-minute encoder 1. The detector 3C that detects deviations performs differential encoding 2S1 using the detection signal d of the detector 2.
The encoding side cuts off the predicted value Xo from the frame memory, selects a zero code for one frame after switching, and then selects the predicted signal in the frame in which the output of the cough differential encoder is delayed by a certain period of time. 3D is a signal selector on the decoding side; 4 is the encoded output Dout of the differential encoder l which differentially encodes the output of the signal selector 3 as a predicted value and the detection of the detector 2; A transmission path for transmitting the signal d; 5 is the detection signal d of the detector 2 transmitted by the transmission path 4;
The signal selector 3D on the decoding side is operated by
This is a decoding unit that performs differential decoding on the encoded signal Din transmitted by the encoded signal Din and outputs a decoded output 5out.

[Effect]

The differential encoder 1 encodes the difference between frames of the input signal using its frame memory and outputs it to the transmission path 4. It detects that the synchronization signal is out of synchronization, determines that the input signal has been switched, and outputs the detection signal d to the signal selector 3C and the transmission line 4.

The signal selector 3C disconnects the predicted value Xo from the frame memory of the differential encoder 1 based on the detection signal d of the detector 2,
The zero code is selected for one frame after switching, and thereafter, the predicted signal in the frame in which the output of the differential encoder is delayed by a certain period of time is selected and output to the differential encoder 1.

The differential encoder 1 outputs the encoded output Dout which has been differentially encoded using the output of the signal selector 3 as a predicted value to the transmission path 4, but if the amount of information generated in the encoded output Dout is too large, a stop signal is sent. to stop the output.

The transmission path 4 sends the output code Dout of the differential encoder 1 and the detection signal d of the detector 2 to the decoding side, and the code Din received at the decoding side is sent to the decoding side by the detection signal d similarly received. Differential decoding is performed using the predicted signal selected by the signal selector 3D to obtain a decoded output Sout.

In the interframe predictive coding/decoding device of the present invention, when the input TV signal Stn of the differential encoder l is switched, the detector 2 detects the input switching and uses the detection signal d to send the signal selector 3C to the signal selector 3C. is driven, the signal selector 3C cuts off the output XO of the frame memory 14, and the input signal S
One frame after switching in in outputs a zero code, and after that, a predicted signal within the frame is output, and after switching, the differential encoder 1 outputs a zero code by using the predicted signal that is not the output value xO of the frame memory. Since the encoded signal is encoded and output to the transmission path 4, the signal selector 3D on the decoding side of the receiving side of the transmission path 4 uses the sent detection signal d to perform the same function as the signal selector 3C on the encoding side. When the decoding unit 5 outputs one correct vertical synchronization signal per frame and the output signal is viewed on a video monitor, there is no deterioration in image quality and the problem is solved.

〔Example〕

FIG. 2 is a block diagram showing the configuration of an interframe predictive coding/decoding device according to an embodiment of the present invention, and FIG. 3 is a time chart for explaining its operation.

In the block diagram of FIG. 2, the differential encoder 1 includes a subtractor 11. Quantizer 12. Adder 13. Frame memory 14
．． Usually, the difference device 11 takes the difference Δ between the frame signal of the input signal Sin and the signal xO of the previous frame stored in the frame memory 14, and the quantizer 12 calculates the difference Δ. is encoded and the code Dout is output to the transmission line 4 via the buffer memory 16.

If the amount of output code Dout generated is too large than the specified value, the buffer memory sends a stop signal 5Tor.
' is output to the quantizer 12 to stop the encoding operation.

Further, the adder 13 normally adds the output code e of the quantizer 12 and the signal of the previous frame stored in the frame memory 14, and writes the sum to the frame memo January 4 as a new signal.

The detector 2 is composed of a vertical synchronization detector 21 that detects deviations of the vertical synchronization signal from a constant period, and as shown in the time chart of FIG.
When the quantizer 12 switches over in frame 2 and generates too much information, the buffer memory sends a stop signal to the quantizer 12, such as 5TOP. Assuming that switching starts in the middle of the second frame 2 and ends in the middle of the sixth frame 6, the detector 2 detects that the period of the vertical synchronization signal is a constant period at the point in the middle of the second frame 2 when the switching occurs. It is detected that the input signal is out of the range, and it is determined that there is a switch in the input signal, and at the end position of the second frame 2' of the switched input signal, a 1-bit signal d of the switching detection signal is generated and sent to the signal selector 3C. send.

The signal selector 3C is composed of a selector 31C with three inputs and one output, and a zero code generator 32C, and normally selects the output χ0 of frame memo January 4 and supplies it to the difference unit 11.
When the input switching is performed in the middle of the second frame, between J'JI of the third frame 3' following the switching frame 2, from the selector 31C to the FM output of the output Xo of the frame memory 14, initially one frame is input. A mixed output is output in which the previous frame F(2) is output and the next is a new frame F(1). Then, from the fourth frame 4' onward of the input signal, the sixth frame 6'
Until then, the FM output is set to "0" from the zero code generator 32C, and the output of the encoder 12 is set to 1, for example, by the delay device 15 instead.
The predicted signal in the frame delayed by the time slot is selected and supplied to the subtractor 11.

Therefore, on the encoding side of the interframe predictive coding/decoding device of this embodiment, the vertical synchronization signal at the leading end of each frame of the input signal when switching the input signal is switched as shown in the synchronization signal. Only one pseudo sync signal is generated at the tip of the third frame 3' of the first frame after the second frame, no pseudo sync signal is generated in subsequent frames, and a pseudo sync signal is generated by switching the input signal. is minimal.

The transmission path 4 includes a multiplexer (MUX) 41. Railroad 42. It is composed of a demultiplexing device (DMUX) 43, and a decoding section 5 for differential decoding and a signal selector 3D on the decoding side are connected to the decoding side of the output of the transmission line 4.

The transmission path 4 transmits the output code Do of the differential encoder 1 on the encoding side.
ut and the detection signal d of the detector 2 are sent to the decoding side of the receiving side, and on the decoding side, the decoding unit 5 uses the predicted signal selected by the signal selector 3D based on the sent detection signal d. The code Dout is differentially decoded to obtain a decoded output Sou L.

In the interframe predictive coding/decoding device of this embodiment, when the input signal Sin of the differential encoder 1 is switched, the vertical synchronization signal detector 21 of the detector 2 detects the input switching and the coding side The selector 31C of the signal selector 3C is driven, the selector 31C sends out a constant predicted signal to the switched input signal Sin, and the differential encoder 1 converts the output of the signal selector 3C into a differential code using the predicted value. Since the encoded output Dout is output to the transmission line 4 along with the detection signal d of the detector 2, on the decoding side of the reception side of the transmission line 4,
A pseudo synchronization signal is generated only once after the frame in which the input signal Sin on the encoding side is switched, and after that, one regular vertical synchronization signal is output per frame. When looking at the decoded output Sout, no deterioration in image quality is observed and there is no problem.

〔Effect of the invention〕

As explained above, according to the present invention, in an interframe predictive coding/decoding device that codes moving images at a low bit rate, even if the input signal is switched, a pseudo signal of a vertical synchronization signal can be generated at most once. Since it is possible to suppress
This has the effect of minimizing deterioration in image quality in low bit rate TV conferences where input signals are switched.

[Brief explanation of the drawing]

/ Fig. 1 is a principle diagram showing the configuration of an interframe predictive coding/decoding device according to the present invention; Fig. 2 is a block diagram showing the configuration of an interframe predictive coding/decoding device according to an embodiment of the present invention; FIG. 3 is a time chart for explaining the operation of the embodiment of the present invention, and FIG. 4 is a block diagram of a conventional interframe predictive code decoding device. In the figure, l is a differential encoder, 11 is a differencer, 12 is a quantizer, 13 is an adder, 14 is a frame memory, 15 is a delay device, 16 is a buffer memory, 2 is a moxibustion device, and 21 is a moxibustion device. A vertical synchronization signal detector; 4 is a transmission path; and 5 is an encoder.

Claims (1)

[Claims] A difference (11) between a signal for one frame of the input signal (Sin) and a prediction signal (Xo) which is a signal of one frame before stored in a frame memory (14) is taken and quantized (12). In the differential encoding transmission method, the encoded differential code (Dout) is transmitted (4), and when the generated amount of the differential code (Dout) exceeds a certain amount, the output operation is stopped and transmitted (4), On the input side of the transmission path (4) of the transmission method, a detector (2) detects synchronization loss of the vertical synchronization signal of the input signal (Sin), and an output (d) of the detector (2) detects the above-mentioned The output (Xo) of the frame memory (14) is cut off, the zero code is selected for one frame, and after that, the output code (Dou) that has been differentially encoded is
a signal selector (3C) for selecting a signal (D) delayed (15) from t) by a certain period of time; The output (d) of the detector (2) is output to the transmission line (4), and on the output side of the transmission line (4), the output (d) of the detector (2) is taken out and output to the decoding frame memory. a signal selector (3D) that selects a zero code for one frame, performs differential decoding, and then selects a decoded signal in which the differentially decoded decoded output (Sc) is delayed by a certain period of time; An interframe predictive coding/decoding device characterized in that a differential output code (Dout) from the transmission path (4) is decoded (5) using an output of a selector (3D).