JPH0771294B2 - Interframe predictive coding transmission system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coded transmission method for highly efficiently encoding and transmitting a television signal, and particularly to a frame in which the influence of an error on a transmission path propagates to the next frame. The present invention relates to an inter-predictive coding transmission method.

[Conventional technology]

Conventionally, in this type of inter-frame predictive coding transmission method, the basic configuration of the inter-frame predictive coding circuit and the inter-frame predictive decoding circuit has a coefficient multiplied by 1 in the prediction coefficient circuit 22 or 54 shown in FIG. However, if a transmission line error occurs, its effect will be propagated to the next frame and will not be eliminated forever. Was being dealt with.

[Problems to be Solved by the Invention]

The above-described conventional interframe predictive coding transmission method has a drawback that the transmission efficiency deteriorates because the intraframe predictive coding is sometimes used for transmission as a countermeasure when an error occurs on the transmission path. It was

[Means for Solving the Problems]

In order to eliminate such a defect, in the interframe predictive coding transmission system according to the present invention, in the interframe predictive coding apparatus, the prediction coefficient control signal received from the interframe predictive decoding apparatus causes a transmission error of a predetermined level or less. If it is, the prediction coefficient control signal is 1, and if the prediction coefficient control signal indicates a transmission error larger than a predetermined level, a prediction coefficient that is not 0 and less than 1 that decreases as the error level increases is derived, and based on this prediction coefficient An inter-frame predictive coding circuit for generating and outputting a first parity signal for error checking for each image signal of each frame, and a differential image signal, a first parity signal and a differential image The inter-frame prediction decoding apparatus has a multiplexing circuit that multiplexes with the prediction coefficient control signal used for signal generation at the same timing. A separation circuit that separates and outputs the differential image signal, the first parity signal, and the prediction coefficient control signal from the received multiplexed signal from the interframe predictive coding device, and the prediction coefficient control signal indicates a transmission error of a predetermined level or less. If the prediction coefficient control signal indicates a transmission error that is larger than a predetermined level, a prediction coefficient that is not 0 and is less than 1 that decreases as the error level increases is derived, and based on this prediction coefficient Corresponding to an image signal of the same frame, and an inter-frame predictive decoding circuit that generates an original image signal from the differential image signal and calculates and outputs a second parity signal for error checking for each image signal of each frame By comparing the first and second parity signals to be processed and giving a predetermined weighting to the comparison result, the transmission error of the received image signal can be reduced. To generate a new prediction coefficient control signal indicating and a predictive coefficient control circuit,
The inter-frame predictive decoding device generates an original image signal by the inter-frame predictive decoding circuit based on the prediction coefficient control signal separated by the separation circuit, and a new prediction coefficient is generated from this image signal by the prediction coefficient control circuit. A control signal is generated and returned to the interframe predictive coding apparatus, and the frame predictive coding apparatus derives a new prediction coefficient by the interframe predictive coding circuit based on the returned prediction coefficient control signal, and A new image signal is encoded based on the prediction coefficient and transmitted to the interframe predictive decoding device via the multiplexing circuit.

Further, the interframe predictive coding apparatus outputs 1 when the prediction coefficient control signal received from the interframe predictive decoding apparatus indicates a transmission error of a predetermined level or less, and the transmission error of the prediction coefficient control signal is larger than the predetermined level. In the case shown, a prediction coefficient that is not 0 and less than 1 that decreases as the error degree increases is derived, a difference image signal is generated based on this prediction coefficient, and error checking is performed for each image signal of each frame. The inter-frame predictive decoding apparatus has an inter-frame predictive coding circuit that calculates and outputs a first parity signal for the following, and a multiplexing circuit that multiplexes the differential image signal and the first parity signal at the same timing. A separation circuit that separates and outputs the differential image signal and the first parity signal from the multiplexed signal from the interframe predictive coding device received via the transmission path; The value is 1 when the prediction coefficient control signal generated based on the image signal of the frame shows a transmission error of not more than a predetermined level, and is large when the prediction coefficient control signal shows a transmission error of more than the predetermined level. A prediction coefficient that is smaller than 0 and less than 1 that is smaller than that is derived, and an original image signal is generated from the difference image signal based on this prediction coefficient, and a second error check is performed for each image signal of each frame. By comparing the first and second parity signals corresponding to the image signal of the same frame with each other and performing a predetermined weighting on the comparison result. And a prediction coefficient control circuit that generates a new prediction coefficient control signal indicating the degree of transmission error for the image signal,
The inter-frame predictive decoding device generates an original image signal by the inter-frame predictive decoding circuit based on the predictive coefficient control signal generated from the image signal of the immediately preceding frame, and by the predictive coefficient control circuit from this image signal. A new prediction coefficient control signal is generated and returned to the interframe prediction coding apparatus, and the frame prediction coding apparatus derives a new prediction coefficient by the interframe prediction coding circuit based on the returned prediction coefficient control signal. At the same time, a new image signal is encoded based on this prediction coefficient and transmitted to the interframe predictive decoding device via the multiplexing circuit.

[Action]

In the inter-frame predictive coding transmission method according to the present invention, it is possible to eliminate the influence of an error that has occurred on the transmission path without substantially reducing the transmission efficiency, and as a result, it is possible to improve the image quality.

〔Example〕

FIG. 1 is a principle diagram for explaining an interframe predictive coding transmission method according to the present invention. In the figure, two inter-frame predictive coding / decoding apparatuses A and B have lines L1 and L2 for transmitting compressed image data and lines L3 and L4 for transmitting error occurrence information on a transmission line separately from the lines L1 and L2. They are opposed to each other.

Consider a case where an error occurs on the transmission line in FIG. In the inter-frame predictive coding / decoding devices A and B, the inter-frame predictive signal is normally controlled to be multiplied by "1" as a predictive coefficient, and the frame memory output signal is simply the inter-frame predictive signal. Interframe predictive coding is performed. The prediction coefficient is a coefficient by which the frame memory output signal is multiplied, and a product of this and the frame memory output signal is an inter-frame prediction signal.

When an error occurs on the transmission line, the error is detected and the transmission line error detection information is transmitted to the other side,
The output signal of the frame memory of the inter-frame predictive coding circuit on the other side and the inter-frame predictive decoding circuit on the own side is controlled by multiplying the value less than "1" as the prediction coefficient, and the leak integration type inter-frame prediction is performed. Encode. In this way, by performing leak integration type inter-frame predictive coding on an error on the transmission path, the influence of the transmission path error can be efficiently suppressed with almost no decrease in transmission efficiency.

As examples of the inter-frame predictive coding transmission method according to the present invention, two examples in which two devices A and B face each other will be shown. FIG. 2 is a block system diagram for explaining the first embodiment of the interframe predictive coding transmission method according to the present invention, and FIG. 3 is a block system diagram for explaining the second embodiment.

First Embodiment FIG. 2 shows two devices A and B facing each other via a transmission line 15. In the figure, 1 and 11 are input terminals to which image signals are input, 2 and 12 are interframe predictive coding circuits, 3 and 14 are multiplexing circuits, 4 and 8 are demultiplexing circuits, and 5 and 9 are interframe predictive circuits. Decoding circuits, 6 and 13 are prediction coefficient control circuits, 7 and 10 are output terminals for outputting image signals, 15 is a transmission line, and 16 and 17 are delay circuits.

The configurations of the inter-frame predictive coding circuits 2 and 12 and the inter-frame predictive decoding circuits 5 and 9 are shown in FIGS. 4A and 4B, and the configuration of the prediction coefficient control circuits 6 and 13 is shown in FIG. . The inter-frame predictive coding circuits 2 and 12 and the inter-frame predictive decoding circuits 5 and 9 are, in addition to the general inter-frame coding / decoding loop, as shown in FIG. It has circuits 25 and 55.

The prediction coefficient circuit 22 is controlled by the prediction coefficient control signal a,
The output signal b of the frame memory 23, which is an input signal, is multiplied by a prediction coefficient to output a prediction signal c.

FIG. 6 shows, as an example of the prediction coefficient circuit 22, the value of the prediction coefficient α for the values a1 to a4 of the prediction coefficient control signal a. In the example shown in the figure, the value of the prediction coefficient control signal a is
If a1 or less, set the prediction coefficient to "1" and set the frame memory
The output signal b of 23 is used as the prediction signal c as it is, and when the value of the prediction coefficient control signal a exceeds a1, the prediction coefficient is set to a small value less than “1” as the value increases and the leak is strongly applied. ing. The prediction coefficient circuit 54 is a similar circuit.

The parity operation circuit 25 calculates the parity for each bit plane for the locally decoded signal d in one frame period and outputs the parity signal e, and the parity operation circuit 55 is also the same.

The delay circuit 16 shown in FIG. 2 is a circuit for delaying the prediction coefficient control signal a and timing it with the differential image signal f, and the delay circuit 17 is also the same.

The prediction coefficient control circuit 6 uses two parity signals g and h.
Is to detect a transmission path error and output a prediction coefficient control signal according to the weight of the error. As shown in FIG. 5, the error bit detection circuit 62 and the weighting circuit 61 are included. It The error bit detection circuit 62 compares the parity signal g and the parity signal h in consideration of delay, and detects the presence or absence of an error for each bit plane. Further, the weighting circuit 61 performs different weighting depending on the presence or absence of an error for each bit plane, and as a result, outputs the prediction coefficient control signal i.

For example, as a simple example, in the case of an N-bit image signal,
The weighting in the parity error of the nth bit (1 ≦ n ≦ N) is w (n) (however, w (1) ≦ w (2) ≦ ...
... ≤w (N-1) ≤w (N)), and the presence or absence of an error in the nth bit (1≤n≤N) is e (n) (however, e
(There is an error when (n) = 1 and no error when e (n) = 0)), the prediction coefficient control signal a as the output can be defined as follows.

a = Σe (n) w (n) The prediction coefficient control circuit 13 operates similarly.

Below, the operation when an error occurs on the transmission line Lb from the device B side to the device A side will be described.

In FIG. 2, the data j sent from the opposite station (device B) is input to the separation circuit 4, and the prediction coefficient control signal a, the compressed image signal k, the parity signal g, and the prediction coefficient control signal l are input.
Is separated into

In FIG. 2, consider the case where an error occurs on the transmission line Lb. Error bit detection circuit 62 of the prediction coefficient control circuit 6
In FIG. 5 (see FIG. 5), the parity signal g separated by the separation circuit 4 and the parity signal h calculated by the parity calculation circuit 55 of the interframe predictive decoding circuit 5 are compared in consideration of delay, and the bitplane is compared. An error is detected for each bit, the weighting circuit 61 weights the result differently for each bit, and outputs the result as a prediction coefficient control signal i. The prediction coefficient control signal i is transmitted to the device B side through the transmission line La.

The prediction coefficient control signal i transmitted to the device B side is separated by the separation circuit 8
Is separated from the transmission data as a prediction coefficient control signal m, input to the prediction coefficient circuit 22 of the interframe predictive encoder 12, and the prediction coefficient is controlled to "1" or a value less than "1" as described above. For example, in the above example, when a relatively high-order bit error occurs, the prediction coefficient is set to a small value less than “1”, leak is strongly applied, and the prediction coefficient is set to “1” for the lower-bit error. The bit error is ignored as, or the control is performed to weaken the leak as a value less than "1" and close to "1". On the other hand, the prediction coefficient control signal m is sent to the apparatus A side through the transmission line Lb as the prediction coefficient control signal p at the timing with the compressed image data n by the delay circuit 17. The prediction coefficient control signal p is separated as a prediction coefficient control signal 1 by the separation circuit 4 in the device A, and is input to the prediction coefficient circuit 54 of the inter-frame prediction decoding circuit 5 to control the prediction coefficient.

In this way, when a transmission path error does not occur, the prediction coefficient is set to "1" and normal interframe coding is performed.
When a transmission line error occurs, both the transmission side and the reception side can be leaked to suppress the influence of the transmission line error propagation.

The above description is the same when an error occurs on the transmission line La.

Second Embodiment A second embodiment described below transmits a prediction coefficient control signal to an inter-frame predictive coding circuit on the opposite station side and performs inter-frame prediction of the own station as compared with the first embodiment. The difference is that the prediction coefficient of the decoding circuit is controlled.

FIG. 3 is a block system diagram of the second embodiment. In the figure, except for the delay circuits 18 and 19, each block operates in the same manner as that of the first embodiment.

In the device A, the prediction coefficient control signal i1 is transmitted to the encoding circuit 12 of the opposite station to control the prediction coefficient, and the delay circuit 18 controls the prediction coefficient of the decoding circuit 5 of the own station.
Delays the prediction coefficient control signal i1 by a predetermined amount.

Consider a case where an error occurs on the transmission line Lb as in the first embodiment. This error is detected by the prediction coefficient control circuit 6 by comparing the two parity signals g and h. Further, the prediction coefficient control signal i1 which is the output of the prediction coefficient control circuit 6 is transmitted to the device B side through the transmission line La and controls the prediction coefficient of the interframe predictive coding circuit 12 as the prediction coefficient control signal m. . On the other hand, the prediction coefficient control signal i1 is delayed by the delay circuit 18 for a predetermined time in order to match the timing when the prediction coefficient of the interframe predictive coding circuit 12 is controlled, and the prediction coefficient control signal q Controls the prediction coefficient of the inter-frame predictive decoding circuit 5 of the local station.

In this way, similarly to the first embodiment, it is possible to control the prediction coefficient on the transmission side and the reception side according to the presence or absence of a transmission path error.

〔The invention's effect〕

As described above, according to the present invention, the predictive coefficient control circuit of the interframe predictive decoding apparatus generates the predictive coefficient control signal indicating the degree of the transmission error with respect to the received image signal and returns it to the interframe predictive coding apparatus. The inter-frame predictive coding circuit of the inter-frame predictive coding apparatus outputs 1 when the received prediction coefficient control signal indicates a transmission error of a predetermined level or less, and the prediction coefficient control signal indicates a transmission error of more than the predetermined level. In this case, a prediction coefficient that is not 0 and less than 1 that decreases as the degree of error increases is derived, a difference image signal is generated based on this prediction coefficient, and the difference image signal is sequentially transmitted to the interframe prediction decoding apparatus. Therefore, it is possible to eliminate the influence of an error that has occurred on the transmission path with almost no reduction in transmission efficiency, and as a result, it is possible to improve the image quality.

[Brief description of drawings]

FIG. 1 is a principle diagram for explaining an interframe predictive coding / decoding apparatus to which the present invention is applied, and FIGS. 2 and 3 are a first embodiment and an interframe predictive coding transmission method according to the present invention. 2 is a block system diagram showing an interframe predictive coding / decoding device, FIG. 4 is a block system diagram showing an interframe predictive coding circuit and an interframe predictive decoding circuit, and FIG. FIG. 6 is a block diagram showing the prediction coefficient control circuit, and FIG. 6 is a characteristic diagram showing characteristics of the prediction coefficient vs. prediction coefficient control signal. 1,11 ...... Input terminal, 2,12 ...... Interframe predictive coding circuit, 3,14 ...... Multiplexing circuit, 4,8 …… Separation circuit, 5,9 …… Interframe predictive decoding circuit, 6 , 13 …… Prediction coefficient control circuit,
7,10 …… Output terminal, 15 …… Transmission line, 16,17 …… Delay circuit.

Claims (2)

[Claims] 1. An interframe predictive coding apparatus which multiplies an image signal of the immediately preceding frame by a predetermined prediction coefficient and then generates and transmits a differential image signal indicating a difference from the image signal of the current frame, and an immediately preceding frame. Interframe prediction that generates and outputs the original image signal by multiplying the image signal of the frame by a predetermined prediction coefficient and then adding the difference image signal received from the interframe coding device via the transmission path. In an inter-frame predictive coding transmission system including a decoding device, the inter-frame predictive coding device, when the prediction coefficient control signal received from the inter-frame predictive decoding device indicates a transmission error of a predetermined level or less, When the prediction coefficient control signal indicates a transmission error larger than a predetermined level, the prediction coefficient is not 0 and is less than 1 and decreases as the error level increases. Derives, generates the differential image signal based on the prediction coefficient,
An inter-frame predictive coding circuit for calculating and outputting a first parity signal for error checking for each image signal of each frame, and used for generating the differential image signal, the first parity signal and the differential image signal A prediction coefficient control signal and a multiplexing circuit that multiplexes at the same timing, and the inter-frame predictive decoding device is configured to obtain a difference from a multiplexed signal from the inter-frame predictive coding device received via a transmission path. A separation circuit that separates and outputs an image signal, a first parity signal, and a prediction coefficient control signal, and 1 when the prediction coefficient control signal indicates a transmission error of a predetermined level or less, and the prediction coefficient control signal is a predetermined level. When a larger transmission error is indicated, a prediction coefficient that is not 0 and is less than 1 that decreases as the error degree increases is derived, and the difference is calculated based on this prediction coefficient. An inter-frame predictive decoding circuit that generates an original image signal from the image signal and calculates and outputs a second parity signal for error checking for each image signal of each frame; First and second
And a prediction coefficient control circuit for generating a new prediction coefficient control signal indicating the degree of transmission error with respect to the received image signal by comparing the parity signals of the The inter-frame predictive decoding device generates an original image signal by the inter-frame predictive decoding circuit based on the prediction coefficient control signal separated by the separation circuit, and from the image signal by the prediction coefficient control circuit. A new prediction coefficient control signal is generated and returned to the interframe predictive coding apparatus, and the frame predictive coding apparatus uses the interframe predictive coding circuit to generate a new one based on the returned predictive coefficient control signal. A prediction coefficient is derived, a new image signal is encoded based on the prediction coefficient, and the inter-frame is encoded via the multiplexing circuit. Inter-frame predictive coding transmission system is characterized in that so as to transmit to the measuring decoder. 2. An interframe predictive coding apparatus which multiplies an image signal of the immediately preceding frame by a predetermined prediction coefficient and then generates and transmits a differential image signal indicating a difference from the image signal of the current frame, and an immediately preceding frame. Interframe prediction that generates and outputs the original image signal by multiplying the image signal of the frame by a predetermined prediction coefficient and then adding the difference image signal received from the interframe coding device via the transmission path. In an inter-frame predictive coding transmission system including a decoding device, the inter-frame predictive coding device, when the prediction coefficient control signal received from the inter-frame predictive decoding device indicates a transmission error of a predetermined level or less, When the prediction coefficient control signal indicates a transmission error larger than a predetermined level, the prediction coefficient is not 0 and is less than 1 and decreases as the error level increases. Derives, generates the differential image signal based on the prediction coefficient,
An inter-frame predictive coding circuit that calculates and outputs a first parity signal for error checking for each image signal of each frame; and a multiplexing circuit that multiplexes the differential image signal and the first parity signal at the same timing. The inter-frame predictive decoding device, a separation circuit for separating and outputting a differential image signal and a first parity signal from the multiplexed signal from the inter-frame predictive coding device received via a transmission path, When the prediction coefficient control signal generated based on the image signal of the immediately preceding frame shows a transmission error of a predetermined degree or less, it is 1, and when the prediction coefficient control signal shows a transmission error of a predetermined degree or more, the error degree. If a prediction coefficient that is not 0 and is smaller than 1 that is smaller as H becomes larger, and an original image signal is generated from the difference image signal based on this prediction coefficient, Both, an inter-frame predictive decoding circuit that calculates and outputs a second parity signal for error check for each image signal of each frame, and the first and second frames corresponding to the image signal of the same frame
And a prediction coefficient control circuit for generating a new prediction coefficient control signal indicating the degree of transmission error with respect to the received image signal by comparing the parity signals of the The inter-frame predictive decoding apparatus generates an original image signal by the inter-frame predictive decoding circuit based on a prediction coefficient control signal generated from an image signal of the immediately preceding frame, and the prediction coefficient from the image signal. A control circuit generates a new prediction coefficient control signal and returns it to the interframe predictive coding apparatus, and the frame predictive coding apparatus, based on the returned prediction coefficient control signal, the interframe predictive coding circuit. A new prediction coefficient is derived by the method, a new image signal is encoded based on this prediction coefficient, and the new image signal is coded through the multiplexing circuit. Inter-frame predictive coding transmission system is characterized in that so as to transmit the frame predictive decoding apparatus.