JPH0832045B2 - Image signal interframe compression device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interframe compression device for image signals used in a video conference system, a videophone, a surveillance system and the like.

2. Description of the Related Art FIG. 2 shows a conventional image frame interframe compression apparatus.

In FIG. 2, the image signal which is an analog signal is A /
It is quantized by the D converter 202 and input to the subtractor 204 and the motion vector detection circuit 217.

The subtractor 204 outputs the difference (prediction error) between this signal and the prediction signal from the prediction circuit 215, and the vector quantization coding circuit
206 uses this set of prediction errors as one vector, selects the closest one representative vector from the patterns of the representative vectors set in advance according to the compression rate, transmits the code to the line, and performs vector quantization. Decoding circuit 209
Output to.

The vector quantization decoding circuit 209 decodes the code from the vector quantization coding circuit 206 into the original prediction error by the representative vector preset according to the compression ratio, and the adder 211 predicts this vector and the prediction error. The prediction signal from the circuit 215 is added and written to the frame memory 213.

The motion vector detection circuit 217 detects a motion vector from the signal from the A / D converter 202 and the data of the previous frame written in the frame memory 213, transmits it to the line, and outputs it to the prediction circuit 215. The prediction circuit 215 outputs a prediction signal based on this motion vector and the data of the previous frame written in the frame memory 213.

Then, on the receiving side, decoding is performed using the same representative vector set in advance in the vector quantization decoding circuit 209 on the transmitting side.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above-described conventional inter-frame compression apparatus for image signals, the same representative vector corresponding to the compression rate is set in advance on both the transmitting side and the receiving side, so the transmitting side is preset. If the image signal is compressed and transmitted at a compression rate different from the compression rate, there is a problem that the receiving side cannot decode the image signal.

In view of the problems of the above-described conventional example, the present invention allows the transmitting side to change the compression rate without changing the pattern of the representative vector set in advance, and to transmit the codes having different compression rates on the receiving side. It is an object of the present invention to provide an interframe compression device for an image signal that can be decoded.

Means for Solving the Problems In order to achieve the above object, the present invention provides a prediction error before being encoded by a first vector quantization encoding circuit,
A second vector quantization coding circuit for vector-quantizing and coding the difference between the prediction errors decoded by the vector quantization decoding circuit is provided, and the code from the first vector quantization coding circuit and the second vector quantization coding circuit are provided. The code from the vector quantization coding circuit 2 is multiplexed according to the compression rate and transmitted.

Effect of the Invention With the above-described configuration, the present invention can change the compression rate without changing the pattern of the representative vector preset in the first vector quantization coding circuit, and can transmit the first vector to the receiving side. By providing a circuit that separates the code from the vector quantization coding circuit and the code from the second vector quantization coding circuit, decoding can be performed without changing the preset representative vector pattern. it can.

Embodiments Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an inter-frame compression apparatus for image signals according to the present invention, and the same components as those shown in FIG. 2 are designated by the same reference numerals.

In FIG. 1, 202 is an A / D converter that quantizes an image signal that is an analog signal, and 204 is a difference (prediction error) between the signal from the A / D converter 202 and the prediction signal from the prediction circuit 215. The subtractor 206 that outputs the set of prediction errors from the subtractor 204 as one vector, selects one nearest representative vector from preset representative vectors according to the compression ratio, and outputs the code. Vector quantization coding circuit, 20
Reference numeral 9 is a vector quantization decoding circuit that decodes the code from the vector quantization coding circuit 206 into the original prediction error using a representative vector preset according to the compression rate.

111 is a subtracter that outputs the difference between the prediction error from the vector quantization decoding circuit 209 and the prediction error from the subtractor 204, and 1
Reference numeral 12 is a vector quantization coding circuit that vector-quantizes the difference from the subtractor 111, and 116 is a compression rate of the code from the vector quantization coding circuits 206 and 112 and the motion vector from the motion vector detection circuit 217. It is a code multiplexing circuit that selects, multiplexes, and outputs to the line.

Reference numeral 211 is an adder for adding the prediction error from the vector quantization decoding circuit 209 and the prediction signal from the prediction circuit 215 and writing it in the frame memory 213. The motion vector detection circuit 217 is an A / D converter. The motion vector is detected from the signal from the device 202 and the data of the previous frame written in the frame memory 213, and the prediction circuit 215 predicts the motion vector and the data of the previous frame written in the frame memory 213. Output a signal.

 Next, the operation of the above embodiment will be described.

In FIG. 1, when transmitting a signal at a relatively high compression rate, the code multiplexing circuit 116 multiplexes the code from only the vector quantization coding circuit 206 and the motion vector from the motion vector detection circuit 217. , Output to the line.

On the other hand, when transmitting a signal at a relatively low compression rate,
The code multiplexing circuit 116 includes vector quantization coding circuits 206 and 11
The code from 2 and the motion vector from the motion vector detection circuit 217 are multiplexed and output to the line.

When transmitting a signal at the above relatively low compression ratio,
On the receiving side, the code from only the vector quantization coding circuit 206 and the motion vector from the motion vector detection circuit 217 can be easily separated, so that they can be decoded.

As described above, according to the present invention, the difference between the prediction error before being coded by the first vector quantization coding circuit and the prediction error decoded by the vector quantization decoding circuit is calculated as a vector. A second vector quantization coding circuit for quantizing and coding is provided, and the code from the first vector quantization coding circuit and the code from the second vector quantization coding circuit are set according to the compression rate. Since the signals are multiplexed and transmitted, the compression rate can be changed and transmitted without changing the pattern of the representative vector set in advance in the first vector quantization coding circuit, and to the receiving side, By providing a circuit for separating the code from the first vector quantization coding circuit and the code from the second vector quantization coding circuit, the code from the first vector quantization coding circuit is set in advance. It can be decoded by the pattern of the defined representative vector, and can be decoded by an inexpensive receiving side with low capability.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an inter-frame compression apparatus for image signals according to the present invention, and FIG. 2 is a block diagram showing a conventional inter-frame compression apparatus for image signals. 111,204 …… Subtractor, 116 …… Code multiplex circuit, 202 …… A / D
Transformer, 206,112 ... Vector quantization coding circuit, 209 ...
… Vector quantization decoding circuit, 211 …… Adder, 213 ……
Frame memory, 215 ... Prediction circuit, 217 ... Motion vector detection circuit.

Claims (1)

[Claims] 1. A first vector quantization coding circuit for vector-quantizing and coding a prediction error of a digital image signal, and a vector quantization for decoding the code from the first vector quantization-coding circuit. A decoding circuit, a frame memory that stores the sum of the prediction error and the prediction image decoded by the vector quantization decoding circuit as the generation of the prediction image of the next frame, and the code by the first vector quantization coding circuit A second vector quantization coding circuit for vector-quantizing and coding the difference between the prediction error before being coded and the prediction error decoded by the vector quantization decoding circuit; and the first vector quantum. An inter-frame pressure of an image signal having a code from the encoding / encoding circuit and a circuit from which the code from the second vector quantization / encoding circuit is multiplexed according to a compression rate and transmitted. Apparatus.