JPS5847911B2 - Interframe coding method for NTSC signals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a simple and efficient interframe coding scheme for NTSC color television signals.

Conventional interframe coding systems for color television signals include a separate coding system that separates the luminance signal and color signal, time-division multiplexes them, and performs interframe coding on the signal sequence, and the NTSC system. There is a method in which direct interframe coding is performed by devising predicted values for a color television signal (hereinafter referred to as an NTSC signal).

The former method has drawbacks such as unavoidable signal waveform distortion during color separation and the large scale of the device.

On the other hand, in the latter method, the polarity of the color subcarrier component is reversed line by line and frame by frame, making it difficult to utilize inter-line and inter-frame correlations, and therefore having the disadvantage that a sufficient degree of band compression cannot be obtained.

In order to eliminate these drawbacks, the present invention performs frame frame drop only for color signals.

The frame correlation is used for both the luminance signal and the color signal, and the drawings will be described in detail below.

In FIG. 1, an analog NTSC signal inputted from an input terminal 11 is converted into a digital signal in an A/D conversion circuit 12, and is supplied to the a side of the switching circuit 13, and also passes through a luminance signal selection filter 14 to the switching circuit 13. b
sent to the side.

The luminance signal selection filter is, for example, a comb filter or a low-pass filter that blocks color subcarrier separation.

The switching circuit 13 alternately selects the NTSC signal and the luminance signal for each frame and sends them to the frame difference circuit 15.

The frame difference circuit 15 generates the original signal from the switching circuit 13, the prediction signal from the switching circuit 16, and a Q difference signal, that is, a prediction error signal.

This prediction error signal is quantized in the quantization circuit 17 and written into the buffer memory 18 as a code of the quantized output level, and is also converted into a prediction error signal including quantization noise caused by the quantization and is converted to a frame addition circuit. 19
sent to.

The prediction error signal from the quantization circuit 11 and the prediction signal from the switching circuit 16 are added by a frame addition circuit 19.

This addition signal is sent to the primary switching circuit 2 in the color signal correction circuit 21.
It is added to the color correction signal from 2 and sent to the frame memory 23.

The switching circuits 13, 16, and 22 operate in synchronization with each other, and when connected to the a side, the NTSC signal is encoded,
When connected to the b side, only the luminance signal is encoded.

The readout output of the frame memory 23 is supplied to the a side of the switching circuit 16. , and are supplied to a transducer 24 that separates the luminance signal and color signal.

The separation waveform device 24 is constructed of, for example, a comb filter, and sends the separated luminance signal to the b side of the switching circuit 16, and sends the separated color signal to the b side of the switching circuit 22.

The a side of the switching circuit 22 is connected to the logic NO".

When the switching circuits 13, 16, and 22 are connected to the b side, the frame difference circuit 15 switches between the input luminance signal and
The difference from the predicted luminance signal read from the frame memory 23 and separated by the waveform generator 24 is calculated, and encoding processing is performed only on the luminance signal.

The prediction NT stored in the frame memory 23 at this time
The color signal in the SC signal is supplied to the color correction circuit 21 through the switching circuit 22, and added to the predicted signal of only the luminance signal obtained by the frame addition circuit 19 to form a predicted NTSC signal for the next frame, which is stored in the frame memory 23. written to.

Therefore, the color signal one frame before is written into the frame memory 236 again.

When the switching circuit 13, 16, 22 is connected to the a side, the difference between the input NTSC signal and the predicted NTSC signal read from the frame memory 23 is taken and encoded.
As mentioned above, this predicted NTSC signal is a color signal from two frames earlier, and its color subcarriers are in the same phase. The error signal level becomes smaller.

Since the switching circuits 13, 16, and 22 are switched for each frame as described above, the contents of the frame memory 23 are rewritten for each frame regarding the luminance signal.
For color signals, the frame memory 23 is stored every two frames.
The contents of will be rewritten.

These code outputs obtained by direct interframe coding for the NTSC signal for each frame and code outputs obtained by interframe coding only for the luminance signal are temporarily stored in the buffer memory 18, and from there, digital signals are transmitted at a constant transmission rate. It is sent out to the transmission line 26 through the output terminal 25.

On the receiving side, the signal input from the digital signal input terminal 21 is temporarily stored in a buffer memory 28, read out from the buffer memory 28, and sent to the Frenim adder circuit 29 at the encoding speed.

The predicted value read from the frame memory 31 is transferred to the switching circuit 3.
The signal is supplied directly to the a side of the switching circuit 32, and is also supplied to the b side of the switching circuit 32 through a transducer 33 that separates the luminance signal and color signal.

In the frame addition circuit 29, if the signal sent from the buffer memory 28 is luminance signal frame data,
The luminance signal is decoded by adding this to the predicted value luminance signal supplied through the b side of the switching circuit 32.

The decoded luminance signal is sent to the color signal correction circuit 34. 35.

The color signal separated by the separator 33 is sent to the switching circuit 36b.
In contrast to this color signal, the color signal before the line (■) is supplied to the b side of the switching circuit 37.

The switching circuits 36 and 37 operate in synchronization with the switching circuit 32.

The color signal correction circuit 34 is for predicted values, and corresponds to the color signal correction circuit 21 on the transmitting side, and when processing the luminance signal, it outputs the color signal from the b side of the switching circuit 36 to the decoded luminance signal. Then create a predicted value of the NTSC signal and store it in the buffer memory 3.
1, and when decoding an NTSC signal frame, "O" is added from the a side of the switching circuit 36 to the decoded signal from the addition circuit 29, so that the decoded signal is written into the frame memory 31 as it is.

Therefore, a predicted value decoded for each frame is written for the luminance signal component in the frame memory 37, but a decoded predicted value for the color signal component is written for every other frame.

Therefore, the encoded output of the NTSC signal is exactly the same as normal decoding.

The color signal correction circuit 35 is for a display, and in the case of a luminance signal processing frame, the decoded luminance signal from the addition circuit 29 and the color signal from the switching circuit 3T after one line, that is, the color from one frame minus one line before. signal is added, NT
The SC signal is decoded.

This decoded digital NTSC signal is converted into an analog signal by a D/A conversion block 38 and outputted to an NTSC signal output terminal 39.

The frame relationships of the signals of each part on the transmitting side and the receiving side are shown in FIGS. 2 and 3, respectively.

In the same figure, the subscript indicates the frame number, and for example, on the transmitting side, only the luminance signal Y in the original signal is encoded and Dy1
The predicted value P at that time is the same as the luminance signal of one frame before, and the predicted value Y is input to the frame memory 23.

The color signal in the predicted signal of one frame before is added to the sum of the predicted difference signal and the predicted difference signal (Y, 10C.

)′. In the next frame, the NTSC signal Y2+C2 including the luminance component and the color component is input as the original signal ■, and the predicted value P at that time is Y1,000Co, which is the same as the previous (yt+co)', The encoded output is DY2C2 including not only the luminance component but also the color component, and the input to the frame memory 23 is (Y2+C2)'.

Changes in the contents of each part on the receiving side can be easily understood from FIG.

In the above explanation, the color signal of the decoded signal for display uses the signal of 1 frame - 1 line before every other frame, but the value of 1 frame - 1 line before and the value of 1 frame + 1 line before are used. Obviously, average values can be used.

It is clear that this invention method can be used in common with other methods.

As explained above, since frame differences are taken for the same sample points of both the luminance signal and the color signal frame, there is an advantage that frame correlation can be completely utilized in still images.

Furthermore, since the brightness signal always uses a value 17 rem ago, there is an advantage that a comparatively good predicted value can be obtained even on a moving screen.

Furthermore, since the encoding processing rule is only two frame periods, there is an advantage that it can be used in common with other band compression methods such as frame frame dropping.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the interframe coding method for NTSC signals according to the present invention, FIG. 2 is a diagram showing the state of each part on the transmitting side, and FIG. 3 is a diagram showing the state of each part on the receiving side. It is a diagram. 1 1: NTSC signal input terminal, 12: A/D conversion circuit, 13, 16, 22, 32, 36, 37: switching circuit, 14, 24, 33: comb filter, 15: frame difference circuit, 1γ: quantization Circuit, 19, 29: Frame force calculation circuit, 21, 34, 35: Color signal correction circuit, 23, 3
1: Frame memory, 18, 28: Puffer memory, 2
5: Digital signal output terminal, 26: Transmission line, 21 digital signal input terminal, 3 8: D/A conversion circuit,
39: NTSC signal output terminal.

Claims (1)

[Claims] 1 A luminance signal selection filter is installed for each of the human-powered NTSC signal and the output signal of the frame memory, and interframe coding is performed on the NTSC signal and the selected luminance signal at the frame alternation, and the frame memory is used as the luminance signal. The chrominance signal is rewritten every frame, and the chrominance signal is rewritten every other frame.For the frame for the NTSC signal of this interframe encoded signal, the decoded signal of that NTSC signal is used, and for the frame for only the luminance signal, the decoded signal of the luminance signal is used. An interframe encoding method for an NTSC signal, characterized in that color signal decoding of neighboring sample points of one frame before is combined and used as a decoded signal.