JPS5931272B2 - Color television signal encoding system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to color television signals (hereinafter simply referred to as color T).
When a color TV signal (hereinafter simply referred to as a Y signal) is digitally encoded and transmitted, the inter-frame correlation of the color TV signal and a luminance signal (hereinafter simply referred to as a Y signal) and two individual chromaticity signals (hereinafter simply referred to as an I signal and The present invention relates to an encoding method that reduces the amount of information to be transmitted by using the correlation between the Q signals (referred to as Q signals) and enables band compression.

When transmitting color TV signals over long distances, digitally encoded transmission is generally used because it can reduce the effects of noise, distortion, etc.; however, digitally encoding color TV signals reduces the bandwidth required for transmission. was greatly expanded, and there were problems in economic efficiency.

For this reason, various methods have been proposed for performing band compression using the statistical properties of color TV signals. For example, N.T.
As in the SC system, PAL system, etc., the three primary color signals (hereinafter simply referred to as R signal, G signal, and B signal) are
Since the amount of information contained in the signal, I signal, and Q signal is small, these two signals are narrow-banded, further modulated using a subcarrier, and the Y signal is A method is known in which signals are transmitted together with frequency multiplexing. By using such a method, the bandwidth required for transmission can be reduced to approximately 5 compared to the case of transmitting three primary color signals. However, since a half-odd integer multiple of the horizontal scanning frequency is used as the subcarrier frequency, the NTSC system
In signals obtained using the PAL system or the like, correlation between frames is lost. Therefore, it is impossible to perform even higher density band compression using direct interframe correlation on these signals. For this reason, a method that performs band compression encoding using the interframe correlation of the Y signal, I signal, and Q signal before modulating the subcarrier, for example, Y,
For each of the I and Q signals, a method can be considered in which only pixels that have changed by a certain threshold value or more between one frame and the next frame are clustered and encoded and transmitted, but in such a method, the clustered position information is , Q signals, respectively, and Y, 1. In a region where the Q signal has a correlation (most of the TV picture signal is considered to be such a region), redundant position information for 11 people will be sent, resulting in poor coding efficiency. In contrast, for the Y signal, only pixels that have changed by a certain threshold value or more between one frame and the next frame are clustered and encoded and transmitted, and the signal and Q signal are only the average value of the part corresponding to the cluster of the Y signal. There is one that multiplexes it into the Y signal and transmits it.

However, in such a method, it is difficult to determine areas where significant changes have occurred between frames (hereinafter simply referred to as significant areas).
Since this is carried out only on the signal, there is no change in the Y signal, and when the signal or Q signal changes, the I signal or Q signal cannot be sent. Moreover, Y. I.
Inter-frame difference values △Y, △I, △Q for each of the Q signals
Find the linear combination result of the absolute value of those two difference values 1△
C! A method can be considered in which the case where =lΔY+lΔ11+lΔQl is equal to or higher than a predetermined threshold value is determined as a significant region, but in this case, the coefficients of the 1ΔYl, 1Δ111ΔQ1 signals are all 1, and Y= 0.30R+0.59G
+0.11B. ．． I-0.60R-0.28G-0,3
2B,. Since Q-0.21R-0.52G+0.31B, for example, a signal is transmitted even when there is a small change in red color, but there is a drawback in that a signal is transmitted only when there is a fairly large change in blue color.

In order to eliminate the above-mentioned drawbacks, the present invention grasps the statistical properties of the color T signal at the stage of the three primary color signals, thereby eliminating color variations, and performs band compression processing based on this statistical property. The purpose of this invention is to provide a digital encoding method that can enhance the band compression effect and further improve the image quality, and will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a block diagram of a color T signal band compression encoding apparatus according to the principles of the present invention.

The encoding device includes a signal separation circuit 101 and a signal conversion circuit 10
2. Presence/absence area detection/control circuit 103, three interframe encoding processing circuits 104, 105, 106, MPX (signal time division multiplexing circuit)) 10r, and buffer memory 108
It is composed of

The current input signal is N, which is a typical color TV signal.
Consider the TSC signal.

This signal is first passed through the signal separation circuit 101 into a Y signal, an I signal, and
It can be divided into Q signals. For convenience, it is assumed that the Y, [, and Q signals are sampled in this circuit at Nyquist intervals and converted into 8-bit PCM signals. The Y, Q signals obtained from the signal separation circuit 101 are supplied to interframe encoding processing circuits 104, 105, and 106, respectively.
It undergoes encoding processing and is converted into a transmission path code. The TV signal is of a type that repeats every frame, Y, I
, Q also have this property, so it is extremely rare for the signals to differ significantly between adjacent frames.
For this purpose, each interframe encoding processing circuit 104, 105
, 106 each have a memory sufficient to store sample values for one frame, and the difference signal ΔY, 106 between the input signal and the signal value of the previous frame stored in this memory is
Δ1 and ΔQ are formed first. The frame difference signals △Y, △I, △Q formed by the interframe encoding processing circuits 104, 105, and 106 are used for encoding processing in each circuit, but at the same time, the signal conversion circuit 102 Based on the principles of the NTSC system, the R. ．． It is converted into G and B signals.

The signal supplied in this case is Y. I. Since the frame difference signals △Y, △I, △Q are for the Q signal, therefore, the signal obtained at the output of the signal conversion circuit 102 is the R. G. It is clear that the frame difference signals ΔR, ΔG, and ΔB for the B signal are obtained. Now, when performing interframe encoding processing, both the transmitting side and the receiving side have memories with the same contents, so it is only necessary to transmit only the parts that have changed significantly between adjacent frames.

In this method, the portion that has changed significantly between adjacent frames is called a significant region, and the ΔY, Δ, and ΔQ signals in the significant region are each appropriately encoded and transmitted. This significant region is determined by the input ΔR in the significant region detection control circuit 103.
, ΔG, and ΔB signals. The absolute values of △R, △G, and △B corresponding to each sample position are first taken, and I
The signals are ΔR1, ΔG1+1ΔB1, and these are further added to give a judgment signal 1ΔC1=lΔR1+1ΔG1+1Δ
It becomes Bl. A signal portion where this lΔCI is larger than a certain threshold value is defined as a significant region, and a signal indicating this significant region is supplied to each interframe encoding processing circuit 104, 105, 106, and the resulting signal is transmitted to each interframe encoding processing circuit 104, 105, and 106. used. Therefore △Y,
For each signal ΔI and ΔQ, only the portion determined to be a significant region is encoded, time-division multiplexed in MPXIO7, and sent to buffer memory 1/08.
It is clear that the significant regions occur at unequal intervals, and therefore the encoded information generated also has unequal intervals.

In order to transmit such information at equal intervals, a buffer memory 108 is installed in this method, and in order to avoid input information from overflowing due to an increase in the storage capacity of the buffer memory, the judgment signal 1△ The determination threshold for C1 changes depending on the amount of memory, and as the amount of memory increases, the threshold also increases and the significant region is controlled to become smaller. As explained above, according to the color television signal encoding method according to the present invention, changes between adjacent frames of a color TV signal are detected by R. It is determined from the linear combination result of frame difference values of G and B signals, and based on this, Y. I. Since the transmission of the Q signal is controlled, it is possible to handle changes based on any of the above signals, perform wide band compression, and provide coding characteristics that are faithful to color. Therefore, it has the remarkable effect of being able to obtain good image quality despite wide band compression.

[Brief explanation of the drawing]

The drawing is a block diagram of a color TV signal band compression encoding apparatus in accordance with the principles of the present invention. 101...Signal separation circuit, 102-...Signal conversion circuit, 103...Significant region detection/Fhl
Leg circuit, 104, 105, 106... Interframe encoding processing circuit, 107... MPX, 108
...Batsufua memory.

Claims (1)

[Claims] 1 In the digital encoding system of color television signals, the interframe difference value ΔR of the three primary color signals R, G, B,
△G, △B are calculated, and the case where the linear combination result of the absolute values of these difference values |△C|=|△R|+|△G|+|△B| is greater than or equal to a predetermined threshold is defined as a significant region. A color television signal encoding method characterized by applying encoding processing to the luminance and two chromaticity signals only within this significant region.