JPH0312838B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a predictive coding method for a color image information signal consisting of a luminance signal and a chrominance signal, such as a composite color television signal, and particularly relates to a predictive coding method for a color image information signal consisting of a luminance signal and a color signal, such as a composite color television signal. This relates to a high-quality intraframe encoding method.

(Prior Art) A separation coding method is an intraframe coding method that is one of predictive coding methods for a color image information signal, for example, a color television signal. To briefly explain this method using an NTSC color television signal (hereinafter referred to as "NTSC signal") as an example, the NTSC signal is once converted into a luminance signal Y and two color signals C ₁ and C ₂ , I and Q. Separate each color signal C ₁ ,
C ₂ is time-compressed by taking advantage of its narrow frequency band, and the time-compressed color signals C ₁ and C ₂ are
is time-division multiplexed during the horizontal blanking period of the luminance signal Y, and in this way, the luminance signal Y and the color signals C ₁ and C ₂ (hereinafter, these two color signals are referred to as "C ₁ signal" and "C ₂ signal" respectively). Intra-frame encoding processing is performed on a time division multiplexed signal (hereinafter referred to as "TDM signal") obtained by time division multiplexing (hereinafter referred to as "TDM signal").

The signal format of the TDM signal in such a system is usually configured as shown in FIG.
That is, the C ₁ signal of the nth line is inserted into the horizontal blanking period of the nth line, and the C ₂ signal of the nth line is inserted into the horizontal blanking period of the (n+1)th line.
The C ₁ and C ₂ signals on the (n+1)th line are ignored. In addition, C ₂ on the nth line
It is also possible to consider a method of ignoring the _C1 signal on the (n+1)th line. Similarly, for the (n+2)th line and subsequent lines, the color signals of every other line are ignored. Regarding the C ₁ and C ₂ signals of the ignored line, the receiving side reproduces the color signal of the ignored line by interpolating them using, for example, the color signals of the preceding and succeeding lines. Note that the Y signal is multiplexed on all lines.

When performing a two-dimensional predictive intra-frame encoding method that utilizes correlation in the horizontal and vertical directions for such TDM signals, conventionally, pixel X was encoded with respect to the pixel arrangement within the frame shown in In this case, when encoding the Y signal, the immediately preceding pixel A, each pixel B on one line in the same field,
The predicted value X^ _Y is constructed as shown _in the following equation ( ₁ ) using
Since C ₁ and C ₂ are arranged in one line alternation,
Pixels B′, C′, on two lines in the same field
The predicted value X^ _C was constructed using D' and the immediately preceding pixel A as shown in equation (2).

X^ _Y =7/8a+1/8d+1/2(c-b)...(1) X^ _C =7/8a'+1/8d'+1/2(c'-b')...
...(2) Here, a, b, c, d and a', b', c', d' are the luminance information pixel values of pixels A, B, C, D and A',
The color information pixel values of B′, C′, and D′ are respectively represented.

In other words, for the pixel value _of pixel
and the pixel value and difference value represented by _the luminance signal at _pixel
Predicted values for each color signal obtained from each formula
The difference values between X^ _C and each pixel value at the pixel X represented by each of these color signals are quantized and encoded.

In this way, conventionally in this type of method, C ₁ , C ₂
When calculating the predicted value X^ _C for each signal, as shown in Figure 2, for the C ₁ and C ₂ signals to be encoded, two lines above the current line of pixel Since pixels B', C', and D' are each used, a two-line memory is required as a component of the color signal prediction circuit, which increases the circuit scale. There were drawbacks such as the need to provide two-dimensional prediction circuits on both the transmitting and receiving sides of the transmission system.

(Object of the Invention) An object of the present invention is to eliminate the drawbacks of the conventional intra-frame encoding method as described above, and to improve the color signal prediction circuit by performing one-dimensional prediction and encoding for the color signal. It is an object of the present invention to provide an intra-frame encoding method for color image information signals that can be simplified and the circuit scale can be reduced.

(Structure and operation of the invention) In order to achieve the above object, the intraframe encoding method of the present invention encodes each of the luminance signal and color signal that constitute a color image information signal, time-division multiplexes the signals, and digitally transmits the signals. In the intra-frame encoding method, a luminance signal is encoded using a two-dimensional predictive encoding method, and a color signal is encoded using a one-dimensional predictive encoding method.

When a luminance signal is encoded by a two-dimensional predictive encoding method and a color signal is encoded by a one-dimensional predictive encoding method, as in the method of the present invention, the one-dimensional predictive circuit for the color signal has two components. Since there is no need to use a line memory, the circuit scale becomes extremely simple and can be sufficiently miniaturized. For example, if the pixel immediately before the pixel to be encoded is used as the one-dimensional predicted value, the one-dimensional prediction circuit for color signals would suffice with a one-pixel delay element such as a D flip-flop, and both transmitting and receiving signals would be sufficient. The configuration is extremely simplified. Moreover, since the luminance signal is encoded using the two-dimensional predictive encoding method, similar to conventional methods of this type, color television can be encoded without any loss in image quality compared to the conventional intra-frame encoding method. Color image information signals such as signals and color facsimile signals can be encoded and digitally transmitted.

(Embodiment) FIG. 3 is a block diagram showing an example of an embodiment of the system of the present invention. In the figure, 1 is a color image information signal, for example, an NTSC signal input terminal, 2 and 24 are filters, 3 is an A/D conversion circuit, 4 is a color separation/time division multiplexing circuit, 5 is a subtracter, and 6 is a quantizer. 7 and 18 are adders, 8 and 19 are luminance signal two-dimensional prediction circuits, 9 and 20 are color signal one-dimensional prediction circuits, 10 are clock generation circuits, 11 and 17 are code conversion circuits, 12 and 16 are digital Interface, 13 is data output terminal, 1
4 is a digital transmission line, 15 is a data input terminal,
21 is a clock reproduction circuit, 22 is a color synthesis/time division separation circuit, 23 is a D/A conversion circuit, and 25 is an NTSC circuit.
Signal output terminals 100 and 101 are switches that are switched by respective switching signals from respective clock reproduction circuits 10 and 21 for both transmission and reception.

In such a configuration, an NTSC signal inputted from an NTSC signal input terminal 1 is band-limited by a filter 2, and then guided to an A/D converter 3 and converted into a digital signal. Next, in the color separation/time division multiplexing circuit 4, two of the luminance signals Y, I, and Q are processed.
The color signals C ₁ and C ₂ are separated into two signals, and the same circuit 4 further converts the color signals corresponding to the luminance signals of every other line as shown in the signal format shown in FIG.
C ₁ and C ₂ are sequentially converted into TDM signals inserted into the blanking period of each line. This TDM
The signal is subtracted from the subtracter 5 by each predicted value from the luminance signal two-dimensional prediction circuit 8 and the color signal one-dimensional prediction circuit 9, which are applied to the subtracter 5 in a time-divisional manner via the switch 100. The difference value is quantized by a quantization circuit 6. The output of the quantization circuit 6 is time-divisionally added to each predicted value by an adder 7, and becomes a locally decoded signal. The locally decoded signal is supplied to a two-dimensional luminance signal prediction circuit 8 and a one-dimensional color signal prediction circuit 9. Luminance signal two-dimensional prediction circuit 8
performs an operation according to a predetermined two-dimensional prediction function, for example, the operation of the prediction function X^ _Y shown in equation (1) above, and outputs the predicted value of the operation result to the switch 100. Further, the color signal prediction circuit 9 uses a predetermined one-dimensional prediction function,
For example, switch the predicted value according to the previous value prediction to 100.
Output to. The switch 100 is controlled by a switch switching signal from the clock generation circuit 10, and outputs the output of the luminance signal two-dimensional prediction circuit 8 during the luminance signal period, and outputs the chrominance signal 1 during the horizontal blanking period when the chrominance signal is superimposed. The output of the dimension prediction circuit 9 is selected and guided to the subtracter 5. The clock generating circuit 10 may be of a well-known configuration that is widely used in the field of digital processing of television signals.
A clock signal generated in phase synchronization with the synchronization signal of the signal is supplied to each section that requires a clock, such as a predictive coding section. On the other hand, as part of this, a switch switching signal for distinguishing between a luminance signal period and a chrominance signal superimposition period is generated, and this signal is supplied to the switch 100 for switching operation.

In this way, a two-dimensional predicted value is used for the luminance signal Y, and a one-dimensional predicted value, for example, the previous pixel value, is used as the predicted value for the color signals C ₁ and C ₂ and the current value is used. quantization circuit 6 time-divisionally quantizes the difference value of
to obtain the quantized output. This quantized output is assigned a predetermined code by a code conversion circuit 11, and is converted into a signal format on a transmission path by a digital interface 12, such as bipolar (AMI: alternate).
mark inversion) code and sent to the digital transmission line 14 via the data output terminal 13.

In the receiving section, the data input from the data input terminal 15 is transferred to the digital interface 16.
After being converted into a signal format that can be decoded in , the code conversion circuit 17 converts it into a signal format that can perform four arithmetic operations, for example, two or more formats. Further, the digital interface 16 separates sampling frequency information on the transmitting side from the received data and supplies this to the clock regeneration circuit 21. The clock reproducing circuit 21 reproduces various clock signals necessary for video decoding based on the sampling frequency information signal from the digital interface 16, and supplies these to each section that requires clock signals. At the same time, as part of this, the clock generation circuit 10 on the transmitting side generates a luminance signal period and a color signal C ₁ ,
The switch 101 selectively directs each signal of the horizontal blanking period in which C ₂ is inserted to the adder 18.
A switch switching signal is generated to control the switch 101, thereby operating the switch 101.

On the other hand, the output of the code conversion circuit 17 is sent to the adder 18 via the switch 101 by the switching operation of the switch 101, and the predicted value regarding the luminance signal is sent from the luminance signal two-dimensional prediction circuit 19 to the signal in the luminance signal period. , and the predicted values from the color signal one-dimensional prediction circuit 20 are respectively added to the color signal in the horizontal blanking period to form a decoded signal.
0 and the color synthesis/time division separation circuit 22, respectively. The two-dimensional luminance signal prediction circuit 19 has the same configuration as the luminance signal prediction circuit 8 of the transmitting section, and the one-dimensional color signal prediction circuit 20 has the same configuration as the one-dimensional color signal predicting circuit 9 of the transmitting section. be.
Furthermore, the same prediction function is used for both transmission and reception.

The TDM signal decoded in this way is once time-division separated into a luminance signal Y and each color signal C ₁ and C ₂ of I and Q in a color synthesis/time-division separation circuit 22.
After time expansion for each color signal C ₁ and C ₂ ,
It is combined with the luminance signal Y so that it becomes an NTSC signal format. This digitized NTSC signal is converted into an analog signal in the D/A conversion circuit 23, band-limited by the filter 24, and sent to the NTSC signal output terminal 25.

In the above embodiment, the predicted value of the luminance signal is based on the equation (1) above, and the color signals C ₁ ,
Regarding C ₂ , we explained the previous value prediction as an example, but
The method of the present invention is not limited to using these predicted values. Furthermore, as for the transmission code, either a fixed length code or a variable length code can be applied. When variable length codes are used, speed smoothing buffer memories are used in the digital interfaces 12 and 16, respectively.

In the above embodiment, a case was described in which an NTSC signal was encoded, but the method of the present invention encodes a PAL signal.
Of course, the present invention can also be applied to a composite color television signal in which a luminance signal and two color information signals are frequency-multiplexed, such as the SECAM method, and a color facsimile signal having the same structure as that color television signal. Not only such a composite color image information signal but also a luminance signal Y and a color signal C ₁ ,
It is also applicable to the case where C ₂ is input separately, and such an embodiment is also included in the present invention. In this case, the color separation/time division multiplexing circuit 4 and the color synthesis/time division separation circuit 22 in the configuration of the embodiment shown in FIG. 3 become unnecessary.

Note that in the method of the present invention, the color signal is NTSC.
Each color signal of I and Q in the signal, (RY), (B
-Y) and other color difference signals and primary color signals, etc., are meant to refer to various color information signals in forms determined by the configuration of the color image information signal.

(Effects of the Invention) As explained in detail above, the system of the present invention time-division multiplexes the luminance signal and chrominance signal of a color image information signal consisting of a luminance signal and chrominance signal, such as a composite color television signal. In the intra-frame encoding method for digitally transmitted color image information signals, the luminance signal is encoded using the conventional two-dimensional predictive encoding method, and the color signal is encoded using the simplest configuration for predicting previous values as a prediction circuit. For example, the encoding is performed by a one-dimensional predictive encoding method that only requires the use of a one-pixel storage element such as a D flip-flop. Therefore, according to the method of the present invention, the two-line memory that was required as a component of the prediction circuit for the chrominance signal in the conventional intra-frame encoding method in which both the luminance signal and the chrominance signal were two-dimensionally predictively encoded is eliminated. Since it can be omitted, the circuit scale of both the transmitting and receiving color signal prediction circuits can be made smaller.Moreover, the luminance signal is subjected to two-dimensional predictive encoding as before, so the image quality is the same as the conventional method. It is possible to encode and digitally transmit a color image information signal with no inferiority compared to the conventional method.

[Brief explanation of the drawing]

Figure 1 is a diagram for explaining the format of a TDM signal in which a luminance signal and two color signals of a color television signal are time-division multiplexed.
A diagram for explaining the pixel arrangement used for two-dimensional prediction in the dimensional predictive coding method, Figure 3 is one of the methods of the present invention.
FIG. 2 is a block diagram showing the configuration of an embodiment. 1...NTSC signal input terminal, 2, 24...Filter, 3...A/D conversion circuit, 4...Color separation/time division multiplexing circuit, 5...Subtractor, 6...Quantization circuit, 7, 18... Adder, 8, 19... Two-dimensional prediction circuit for luminance signal, 9, 20... One-dimensional prediction circuit for color signal, 10... Clock generation circuit, 11, 1
7... Code conversion circuit, 12, 16... Digital interface, 13... Data output terminal, 14
...Digital transmission line, 15...Data input terminal, 21...Clock regeneration circuit, 22...Color synthesis/time division separation circuit, 23...D/A conversion circuit,
25...NTSC signal output terminal, 100, 101...
...Switch.

Claims (1)

[Claims] 1 A color image information signal is separated into a luminance signal for each line and a chrominance signal for each interval line, each coded, time-division multiplexed and digitally transmitted, decoded on the receiving side, and then an intra-frame code that assembles each signal. In the coding/decoding method, the transmitting unit calculates the luminance signal of the current pixel by using coded pixels on the same line and coded pixels one or more lines above the current pixel to be coded. A prediction signal is constructed, the prediction error signal is encoded and transmitted, and for the color signal, a current pixel prediction signal is constructed using encoded pixels on the same line as the current pixel to be encoded. , the prediction error signal is encoded, and in the receiving section, for the luminance signal, the current pixel is reproduced by adding the received prediction error signal of the current pixel and the two-dimensional prediction signal constructed by the same method on the transmitting side. However, regarding the color signal, intra-frame encoding decoding is characterized in that the current pixel is reproduced by adding the received prediction error signal of the current pixel and a one-dimensional prediction signal configured by the same method as that on the transmitting side. method.