KR960013228B1 - Abnormal display preventing apparatus at channel selection of digital television - Google Patents

Abstract

The apparatus is for preventing of displaying an abnormal picture when changing channel. An interface unit capable of matching data provides a signal with a variable length out of a buffer and an inverse quantizer unit inversely quantizes a decoded output signal. An output signal from the inverse quantizer is inversely transformed by an IDCT unit, of which output signal is moving compensated by a frame memory and a moving compensation unit. A control unit resets all the functions of units with the inputs of an intraframe signal, a frame synchronization signal and a channel change signal, and provides an active/inactive signal to control the frame memory and moving compensation unit.

Description

Abnormal screen display prevention device when changing channel of digital television

1 is a block diagram of an apparatus for preventing abnormal screen display when changing a channel according to the present invention.

FIG. 2 is a detailed configuration diagram of the frame memory and the motion compensation unit of FIG.

3 is a signal waveform diagram of each part of FIG.

* Explanation of symbols for main parts of the drawings

1 interface 2 buffer

3: variable length decoder 4: control unit

5: inverse quantizer 6: IDCT unit

7: frame memory and motion compensation unit 61: DPCM

62,63: frame memory

The present invention relates to an apparatus for preventing abnormal screen display at the time of channel change, which prevents the abnormal screen from being displayed at the time of channel change in a digital TV.

When a digital TV such as a high-definition television (HDTV) is put into practical use and broadcasting starts, a plurality of broadcasts will be transmitted through a plurality of channels as in the current broadcast transmission method. By the way, in the conventional general analog broadcasting, even if the channel is changed, it is possible to display the current input signal immediately.However, in the case of the digital method, a large amount of data is specified instead of directly displaying the screen with only the current input data. As a motion compensation method is used as a technique for data compression method, a normal screen can be displayed only when data of a previous frame is stored in a predetermined storage device.

At the moment the channel is changed, there is no interconnection between the previously received data and the data currently received through the new channel, so that the configuration requirements of the frame data cannot be captured. If the system receives such data, the system goes down. To be. In other words, when a user changes a channel in a digital TV, the screen is not displayed completely immediately, but is displayed abnormally and then restored. This is because the input data at the time of channel change is caused by the frame of the previous channel by the moving compensation, not the intra frame. The picture is then restored to the normal picture after the intra frame has been entered.

Accordingly, an object of the present invention is to provide an apparatus for preventing abnormal screen display when changing a channel of a digital TV, which prevents an abnormal screen from being displayed by controlling the display memory when changing a channel.

In order to achieve the above object of the present invention, the apparatus for preventing abnormal screen display when changing a channel according to the present invention comprises: interface means for performing a data matching function; Buffer means for buffering a signal output from the interface means; Variable length decoding means for variable length decoding the signal output from the buffer means; Inverse quantization means for inversely quantizing a signal output from said variable length decoding means; IDCT means for performing an Inverse Discrete Cosine Transform (IDCT) on a signal output from the inverse quantization means; Frame memory and motion compensation means for motion compensation of the signal output from said IDCT means; Input the intra signal, the frame synchronizing signal, and the channel change signal output from the variable length decoding means, so that the interface means, buffer means, variable length decoding means, inverse quantization means, IDCT means, frame memory and motion compensation means And a control means for outputting a reset signal for resetting the signal and an active / inactive signal for controlling the frame memory and the motion compensating means.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

FIG. 1 is a block diagram of an apparatus for preventing abnormal screen display when changing a channel according to the present invention, FIG. 2 is a detailed block diagram of a frame memory and a motion compensation unit of FIG. 1, and FIG. 3 is a signal waveform diagram of each part of FIG. .

As shown in FIG. 1, the apparatus for preventing abnormal screen display when changing a channel according to the present invention includes an interface unit 1, a buffer 2, a variable length decoder 3, a control unit 4, and an inverse quantizer 5; And an Inverse Discrete Cosine Transform (IDCT) 6, a frame memory, and a motion compensation unit 7.

The bit string input through the channel is output to the buffer 2 through the interface unit 1 performing the signal matching function, and the signal buffered in the buffer 2 is variable length decoded by the variable length decoder 3 and inversed. It is output to the quantizer 5. The dequantized signal in the inverse quantizer 5 is subjected to IDCT processing in the IDCT unit 6, input to the frame memory and the motion compensation unit 7, and output for motion compensation and display. The variable length decoder 3 variable length decodes the signal output from the buffer 2 and outputs it to the inverse quantizer 5, and simultaneously outputs an intra frame signal to the control unit 4. The control unit 4 receives the in-frame signal from the variable length decoder 3, receives the frame synchronization signal and the channel change signal from the outside, and as shown in FIG. 3, the reset signal and the active / inact (act / inact) signal. Signal is generated and provided to the frame memory and the motion compensator (7). That is, after the channel change signal is input, each block (1, 2, 3, 5, 6, 7) of the system is reset in synchronization with the next frame synchronization signal. The system then starts a new operation from the beginning and all previous data is reset so that the system does not go down.

As shown in FIG. 2, the frame memory and the motion compensator 7 have a DPCM unit 61 and a DPCM unit for processing a differential pulse code modulation (DPCM) output from the IDCT unit 6. Frame memory 62 for storing signals output from 61 and frame memory 63 for storing signals output from the frame memory 62 and outputting them to the DPCM 61 again. The frame memory 62 stores the data of the frame processed for transmission from the DPCM 61, and the frame memory 63 stores the data of the previous frame to output the motion compensated output to the DPCM unit 61 and display it. Output for The frame memory 63 is controlled by an active / inactive signal output from the controller 4. The active / inactive signal becomes inactive when the system is reset after inputting the channel change signal as shown in FIG. 3, and then is activated in the next frame synchronizing signal after the in-frame signal is input. Here, the active and inactive operations mean an operation capable of recording data in a memory and an operation that cannot be recorded. That is, when the channel is changed, when the frame memory 63 is inactivated, the data transmitted to be displayed becomes the data of one frame before the channel change, since new data is not recorded in the frame memory 63. The data of the previous one frame is continuously displayed. That is, the user does not show the process of recovering the screen abnormally by the channel change.

Making the active state at the next frame synchronization after the intra-frame signal generation means that data starts to be written to the frame memory 62 when the intra-frame signal is generated, so that the data of the frame is still in the frame memory 62. Is in the unrecorded state, and in the next frame synchronization signal, the in-frame signal is recorded in the frame memory 62, and normal operation starts from this time.

In addition, the reason for inactivating in accordance with the frame synchronization signal is that if the synchronization is not matched, the data of two frames are displayed in an inactive state in the state of coexistence in the frame memory 63. The reason why the reset signal is generated in the 'low' level state during one cycle of the frame synchronization signal in accordance with the frame synchronization as shown in FIG. 3 is to increase the pulse width of the reset signal sufficiently to increase the reset time. This is because if the channel is sufficiently changed and the channel is reset as soon as the channel is changed, the entire system including the buffer 2 is reset and the reset state data is input to the frame memory 63 which is still active.

The present invention configured and operated as described above has an effect of preventing an abnormal screen from being displayed when a channel is changed.

Claims (4)

Interface means (1) for which data performs a matching function; Buffer means (2) for buffering signals output from said interface means (1); Variable length decoding means (3) for variable length decoding the signal output from the buffer means (2); Inverse quantization means (5) for inversely quantizing the signal output from said variable length decoding means (3); IDCT means (6) for inverse Discrete Transform (IDCT) of the signal output from said inverse quantization means (5); A frame memory and motion compensating means (7) for motion compensating the signal output from said IDCT means (6); Input the intra frame signal, the frame synchronizing signal and the channel change signal outputted from the variable length decoding means 3, the interface means 1, the buffer means 2, the variable length decoding means 3, and vice versa. A reset signal for resetting the quantization means 5, the IDCT means 6, the frame memory and the motion compensating means 7, and the active / inact acting to control the frame memory and the motion compensating means 7. The control means (4) for outputting a signal to prevent abnormal screen display when changing the channel of the digital TV. 2. The apparatus of claim 1, wherein the frame memory and motion compensation means (7) comprise: DPCM means (61) for performing differential pulse code modulation (DPCM); First frame storing means (62) for storing the currently processed input data to be transmitted output from said DPCM means (61); A second frame storage means (63) for storing data of the previous frame output from the first frame storage means (62) and transmitting the data to the DPCM means (61) under the control of the control means (4). Device to prevent abnormal screen display when changing channel of TV. The abnormal screen display of changing the channel of the digital TV according to claim 1, wherein the reset signal is generated during one cycle of the frame synchronization signal in synchronization with a next frame synchronization signal after the channel change signal is input. Prevention device. 2. The method of claim 1, wherein the active / inactive signal is in an inactive state in synchronization with a next frame synchronization signal after the channel change signal is input, and then in the next frame synchronization signal after the in-frame signal is input. Device for preventing abnormal screen display when changing the channel of the digital TV, characterized in that the active state in synchronization.