JPS5936488A - Predictive encoder for television signal - Google Patents

Abstract

PURPOSE:To multiplex new information without deteriorating the encoding characteristic of a predictive encoder, by using the predictive encoder having a specific quantizer operated at a predetermined period in a blanking period of a television signal and determining suitably the quantizing level. CONSTITUTION:The television signal from an input terminal 1 is sampled and quantized at an A/D converter 3, the difference with an output of the predictive circuit 5 is taken at a difference circuit 4 of the predictive encoder. An output of the difference circuit 5 is quantized at a nonlinear quantizing circuit 6 in 5-bit and a nonlinear quantizing circuit in 3-bit, i.e., a specific quantizer 7, and either of outputs of the quantizing circuits 6, 7 is selected at a switch 8 with a switching signal from a pulse generator 2 and inputted to the predicting circuit 5 and a buffer 9. A multiplexing circuit 10 multiplexes the information at an input terminal 11 on the output of the buffer memory 9 and transmits the result to a transmission circuit from an output terminal 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a predictive encoding device for encoding television signals.

A predictive encoding device is a type of encoder that compresses the band of a television signal and converts it into a digital signal. In such a predictive coding device, when a request arises to add new transmission path frame bits or error correction bits or to multiplex audio or data signals due to transmission path conditions, the encoding characteristics for television signals may deteriorate. It is necessary to meet this requirement without causing any problems.

Conventionally, as a method to meet such requirements, there has been a method of setting several samples in the blanking interval to a fixed value, reducing the amount of information generated in the television signal, and obtaining time slots (surplus information bits) necessary for new information. However, in such a method, a part of the blanking interval is set to a fixed value, and therefore, it is not possible to satisfy the request from those involved in broadcast television to faithfully transmit a waveform. Another method is to lower the sampling frequency of the predictive encoder to some extent to obtain time slots for multiplexing new information. However, with this method, by changing the sampling frequency,
This requires changing the prediction function.

Significant hardware design changes were required, and there was a drawback in that high-frequency characteristics deteriorated in terms of encoding characteristics.

The purpose of the present invention is to maintain constant transmission speed and image quality through encoding, and to add new information bits such as error correction codes and new frame synchronization signals without changing the hardware of the television signal encoding system. The object of the present invention is to provide a predictive encoding device that can be easily performed.

According to the present invention, there is provided a predictive encoder having a specific quantizer that operates during a predetermined period within a blanking interval of a television signal, a buffer memory that stores an output of the predictive encoder, and an output of the buffer memory. and a multiplexing circuit that multiplexes new information with new information. , a predictive encoding device for television signals is obtained, which is characterized in that new information can be multiplexed without deteriorating the encoding characteristics of the predictive encoder for picture signals.

With such a configuration of the present invention, bits for a new transmission path frame and bits for error correction can be added without changing the parameters for the image signal portion of the predictive encoder that have already been set. Therefore, new information bits can be added by setting the operating period of a specific quantizer according to the number of bits to be added.

Moreover, no deterioration in image quality occurs. This is because the prediction of the predictive encoder is accurate for the signal in the blanking interval excluding the part that changes in a pulse-like manner9, and the distribution range of the prediction error is small, and the quantization characteristic with a narrow dynamic range can be applied. For this reason, the pulse-like changing part of the blanking interval is selected as the interval in which the specific quantizer operates. In addition, if the input TV signal is a color TV composite signal,
Higher order measurement functions are used.

As described above, according to the present invention, it is possible to easily add error correction bits and change the transmission line frame due to unique circumstances on the transmission line side by changing the transmission line interface part.

Next, the present invention will be explained using the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of a predictive coding device for television signals according to the present invention.

In FIG. 1, an input television signal from an input terminal 1 is sampled and quantized by a VD converter 3 using a sampling clock that is phase-synchronized with the input television signal generated by a pulse generator 2, and then converted into a predictive code. A difference circuit 4 calculates the difference between the output of the prediction circuit 5 and the output of the prediction circuit 5. The output of the difference circuit 4 is quantized by a 5-bit nonlinear quantization circuit 6 and a 3-bit nonlinear quantization circuit, that is, a specific quantizer 7, and is quantized by a switching signal from the norm pulse generator 2. The output of either the quantization circuit 6 or 7 is selected by the switch 8, and the output of the prediction circuit 5 and /J buffer memory 9 is selected.
is input. In the multiplexing circuit 10, the graphic memory 9
The output from the input terminal 11 is multiplexed with the information from the input terminal 11, and sent to the transmission line through the output terminal 12. As the prediction function of the prediction circuit 5, a high-order sub-measurement function is selected that can predict well the color components of a color television signal.

The 3-bit quantization circuit 7 has the same fine quantization characteristics as the 5-bit quantization circuit 6.

FIG. 2 is a diagram for explaining the present invention. FIG. 2a shows a television signal waveform, 2 indicates a blanking section, and 2 indicates a picture signal section.

The output of the 3-bit quantization circuit 7 is selected during a certain period 1, for example, period A of the blanking interval H.

In section H, the prediction by the prediction circuit 5 is very accurate in the parts other than the rising and falling sections of the synchronizing signal, so that the waveform can be faithfully transmitted using the characteristics of the 3-bit quantization circuit 7. A pulse for writing and reading data into the buffer memory 9 is generated by the pulse generator 2 based on the horizontal synchronizing signal of the input television signal.

The write/read operation is started at the timing of the pulse shown in FIG. 2, and this becomes the starting point of data for one day data frame on the transmission path (see FIG. 2C).

The multiplexing circuit 10 multiplexes the audio data S and the transmission line frame bits F from the input terminal 11 onto the output of the buffer memory 9, and sends the multiplexed data to the transmission line through the output terminal 12. FIG. 2d shows the structure of a digital frame sent to the transmission path. The capacity of the graph memory 9 in FIG. For example, sampling frequency f8
If f8=680fH (fH is the horizontal scanning frequency), the digital data generated within one horizontal scanning section is 5 bits (DPCM) x 680 samples=3400 bits. If a specific quantization circuit, that is, a 3-bit quantization circuit 7, is selected for 18 samples within the blanking interval ■, 18x(5-3)-36 extra bits are created, and 12 bits are used for frame synchronization and 24 bits are used for audio. If it is possible to allocate it to data, it is sufficient to prepare a buffer memory with a capacity of 36 bits or more.

As described above, according to the present invention, additional data can be inserted within the range of the number of samples in the section H in FIG. Can be multiplexed. Further, since the human output of the buffer memory is calculated in the horizontal scanning period, the capacity of the buffer memory is required at least as much as the information bits added within one scanning period.

In this embodiment, the number of quantization circuits is 2, 3 bits, 5
Although the explanation is based on a bit quantization circuit, it goes without saying that the invention is not limited to this. Further, although the horizontal blanking interval is used as the period during which the specific quantizer operates, the present invention is not limited to this, and a vertical blanking interval may also be used. In this case, the capacity of the buffer memory becomes large. In this embodiment, an A/D converter is provided in the input section, and the predictive encoder is constructed entirely of digital circuits; however, the present invention is not limited to this; a nonlinear A/D converter is provided in the quantization circuit, and the It can also be constructed as a hybrid type in which an f)/A converter is provided at the circuit output. Also in this example.

It is called a specific quantizer and has one quantization circuit, but it adds a limiter function to the quantization circuit of a conventional predictive encoder and outputs the lower two bits and the sign bit as the output of the specific quantizer. It's okay.

Furthermore, in this embodiment, the case where the number of samples within one horizontal scanning period of the television signal is constant is explained, but when the number of sampling points within one horizontal scanning period varies, the buffer memory as described below is used. It is necessary to control the operating period of a specific quantizer based on the buffer occupancy rate of , and to send information on the operating period of the specific quantizer to the receiving section. The number of samples operated by a specific quantizer is added to the frame sent to the transmission path,
The position of the sampling point between the transmitter and the receiver is determined in accordance with the number of samples. Then, the buffer memory occupancy rate of the buffer memory is monitored, and if the buffer memory occupancy rate at the end of one horizontal scanning period is 1 or more, the number of samples operated by the specific quantizer in the next horizontal scanning period is set to 2, for example. Increase the number of samples, and vice versa, decrease the number of samples by, for example, 2 samples.

Further, the capacity of the buffer memory is set to twice the additional information bits generated in one horizontal scanning section, and the operation is controlled to start when the buffer memory occupancy rate is high when the device is powered on.

According to one aspect of the present invention, as is clear from the above description.

This has the effect of keeping the transmission speed and encoding image quality constant, and also allowing new information bits such as error correction codes and new frame synchronization signals to be easily added without changing the hardware of the television signal encoding system.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a predictive coding apparatus for television signals according to the present invention, and FIG. 2 is a diagram for explaining the present invention in detail. Explanation of symbols: 1 is the input terminal, 2 is the pulse generator. 3 is an A/D converter, 4 is a difference circuit, and 5 is a prediction circuit. 6.7 is a quantization circuit, 8 is a switch, 9 is a buffer memory, 10 is a multiplexing circuit, 11 is an input end, and 12 is an output end. 47

Claims (1)

[Claims] 1. A predictive encoder that operates during a predetermined period within a blanking interval of a television signal and has a specific quantizer with a small number of quantization levels, a buffer memory that stores the output of the predictive encoder, and the buffer memory. A predictive coding device for television signals, comprising a multiplexing circuit for multiplexing the output of the 1000 and other information.