KR950012641B1 - Digital image reproducing system and method for special fuction - Google Patents

Abstract

a recording unit for storing movement compensation compressed and coded frame data and providing the frame data read by a control signal to an output side thereof; a buffer in which the movement compensation compressed and coded frame data are sequentially stored; a decoding unit for inverse-quantizing and inverse-discrete cosine transforming(DCT) the quantized DCT conversion coefficients by decoding the movement compensation compressed and coded frame data and for restoring the quantizing result to an original signal before the coded data to provide the signal to a display; and a control unit for supplying the control signal which reads the frame data and for selectively controlling a data restoration operation of the decoding unit.

Description

Digital Video Playback Device for Special Functions and Its Playback Method

1 is a block diagram of a digital image reproducing apparatus for a special function according to a preferred embodiment of the present invention.

FIG. 2 is a detailed block diagram of a decoding unit in the digital video reproduction field shown in FIG.

3 is a diagram for explaining an active signal for a still picture and a 1 / 2x low speed picture signal according to the present invention;

4 is an interframe transmission flowchart illustrating a frame displayed during high speed playback according to the present invention.

* Explanation of symbols for main parts of the drawings

10: recording medium 12: buffer

14 protection unit 16 control unit

20: variable length decoder 22: inverse quantization unit,

24: reverse DCT 2: motion compensation

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital video player, and more particularly, to a digital video player for a special function of digitally processing video signals such as high-definition television (HDTV), video phones, and the like, and a method of playing the same.

In the conventional video recording apparatus, the digital video data is usually A / D converted and then the data is recorded on the recording medium. However, in this method, since the data to be recorded on the recording medium is only A / D converted data, the amount of data to be actually recorded is enormous. For this reason, in the case of a video signal having a large amount of data, such as HDTV or videophone, high-density recording must be performed on the recording medium itself or the capacity of the recording medium must be increased.

As is well known in the art, the transmission and processing of discrete image signals can maintain better image quality than analog signals. When a video signal consisting of a series of image "frames" is represented in digital form, a significant amount of data must be transmitted, especially for high quality television.

Therefore, as described above, in order to reduce a large amount of data generated in an apparatus for transmitting a moving picture digitally, such as an HDTV or a video phone, a high rate data compression encoding method is used. As such a data compression encoding method, as is well known in the art, motion compensation encoding, such as discrete cosine transform (DCT) using sub-frame spatial image correlation of image data, subband encoding, and temporal correlation of image data, Inter-frame difference coding and variable length coding.

Therefore, when the digital video recording apparatus compresses the data using the data compression encoding method as described above, the amount of data to be recorded (or transmitted) is significantly reduced, thereby solving the above-mentioned problems in the prior art.

However, in the above-described conventional apparatus, when data is compressed and recorded on a recording medium by the data compression encoding method as described above, a special function such as slow screen playback and fast learning playback on a recording medium on which compression-coded video data is recorded is recorded. Due to the inability to play back images, the method of simply recording A / D-converted video data onto a recording medium has been used.

Accordingly, an object of the present invention is to provide a digital image reproducing apparatus for a special function capable of special reproduction of a video signal recorded on a recording medium by motion compensation compression coding.

Another object of the present invention is to provide a method of reproducing image data in a digital image recording apparatus in which motion compensated compression encoded image data is recorded.

According to an aspect of the present invention, there is provided a digital image reproducing apparatus for reading and reproducing frame data of a motion compensated compression protected image recorded on a recording medium. A storage medium for storing frame data read out on the basis of a control signal for reading stored frame data, the storage medium sequentially storing the motion-compensated compression-coded frame data read out from the recording medium at the time of reproduction. buffer; Inversely quantize and inverse DCT the quantized DCT transform coefficients obtained by variable length decoding on each of the motion compensated compression coded frame data provided from the buffer, and then perform motion compensation to the original signal before encoding. A decoder for restoring and providing it to the display side; And providing the control signal for reading the frame data to the recording medium in the normal playback mode or the special playback mode, and selectively controlling the data recovery operation of the decoder according to the mode in the special playback mode. And a control unit, wherein the control unit temporarily stops the restoration operation of the decoding unit in the stop mode of the special playback mode and simultaneously buffers the buffer from the recording medium based on the data fullness state information provided from the buffer. Control the data transfer to the recording medium, and alternately control the recovery operation and the stop operation of the decoding unit in the low speed mode of the special playback mode, and at the same time to the recording medium based on the data fullness state information provided from the buffer. To control the transfer of data to the buffer, And a read control signal for reading only the specific frame data having no motion vector information on the recording medium so that only the specific frame data can be restored by the decoder in the fast mode. Provided is a digital video reproducing apparatus.

According to another aspect of the present invention, a digital image reproducing method of reading frame data of a motion ancestor compression-coded image recorded on a recording medium and reconstructing and reproducing the original signal before being encoded by the decoding means. In the normal playback mode, the frame data of the motion compensated compressed coded image recorded on the recording medium is read, and then restored to an original signal through a decoding means and provided to the display side. In the mode, the restoring operation of the decoding means is temporarily stopped to provide only one specific frame data restored to the display side and at the same time based on data fullness state information provided from a buffer provided on the output side of the recording medium. Transfer of data from the recording medium to the buffer Controlling process; By alternately controlling the restoring operation and the stopping operation of the decoding means in the low speed mode of the specific reproduction mode, the respective frame data restored during the restoration operation are repeatedly provided to the display side sequentially from the buffer. Controlling data transfer from the recording medium to the buffer based on data fullness status information; And the specific frame having no motion vector information among the frame data recorded on the recording medium so that only the specific frame data in the decoding means can be restored and provided to the display side in the high speed mode in the special playback mode. There is provided a digital video reproduction method for a special function consisting of reading only data and providing the data to the decoding means.

The above and other objects and various advantages of the present invention will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings by those skilled in the art.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

1 is a block diagram of a digital image reproducing apparatus for a special function according to a preferred embodiment of the present invention.

In the figure, the recording medium 10 is for storing motion compensation compression coded image data, and between the recording medium 10 and the decoding unit 14 for reconstructing the compression coded image data to an original signal. The buffer 12 is provided.

The reason why the buffer 12 is provided between the recording medium 10 and the decoding unit 14 is that the video data recorded on the recording medium in the above-described conventional method is only A / D converted video data. In the present invention, each frame of the actual image has the same amount of data. However, in the present invention, the image data recorded on the recording medium 10 is image data compressed and coded by MC-DCT and variable length coding. This is because the actual amount of generated data differs for each, and it is necessary to appropriately adjust it at the front end of the decoder 14 at the time of restoration for reproduction of the recorded video data.

That is, in the digital image reproducing apparatus according to the present invention, in the general reproducing mode, only the recording medium 10, the buffer 12, and the decoding unit 14 can reproduce the screen, but special reproduction, for example, In the case of a slow picture or a still picture, the time required for the decoding unit 14 to read the image data stored in the buffer 12 is slowed down, and thus the buffer 12 receiving the read data from the recording medium 10 at a constant speed. This can lead to a pool of data. Therefore, in the buffer 12, substantial data loss is caused due to the occurrence of the data pool state, so that wrong data is input to the decoder 14, and image quality deterioration may occur in the actual reconstructed image.

Therefore, in the present invention, the buffer 12 is provided between the recording medium 10 and the decoding unit 14 in order to prevent data loss due to the data pool state in the buffer 12 during special reproduction as described above. The control unit 16 provides the control unit 14 with a control signal for a data restoration operation suitable for the special reproduction based on the data fullness state information provided from the buffer 12, and also at the reproduction medium 10. Control the transfer of data to the buffer 12. That is, the controller 160 checks the fullness of the data stored in the buffer 12 in order to smoothly perform a special function such as slow picture playback or still picture playback, and based on the check result, the recording medium 10 Control the data transfer to the buffer 12, and provide the control unit 14 with a control signal for the restoration operation required when performing a special function.

FIG. 2 shows a detailed block diagram of the decoder 14 of FIG. 1 restoring image data from the buffer 12 based on the control signal from the controller 16. As shown in FIG. As shown in the figure, the decoder 14 included in the present invention, as is well known in the art, is a variable length decoder for variable length decoding the variable length coded image data in the encoder of the transmitting side (20), an inverse quantization unit 22 and an inverse DCT unit 24 for restoring the quantized DCT transform coefficients output from the variable length decoding unit 20 to the original signal (pixel data) before encoding; A frame memory motion compensation unit 26 performs motion compensation by performing motion compensation between temporally continuous frames (eg, the current frame and the previous frame) using the motion vector. Therefore, in the reproduction mode or the special reproduction mode, the compressed coded image data read out from the recording medium 10 and provided from the buffer 12 as described above, before being encoded by the motion compensator 14, is obtained. The signal is outputted to a display unit, not shown, for restoring to the next monitor.

For example, in the still picture reproducing mode, the controller 16 provides a control signal to the decoder 14 to freeze the picture. That is, as shown in FIG. 3, if the signal transmitted from the control unit 16 to the decoding unit 14 for the reconstruction operation of the video data is an active signal, in the case of the normal playback mode, the control unit 16 is the same. As shown at the top of the figure, a high level active signal (control signal) is provided to the decoder 14, and in the case of the still picture playback mode, the controller 16 supplies the frame synchronization signal to the decoder 14. The low level active signal is synchronized.

In this case, the control unit 16 stops the data restoring operation of the decoding unit 14 so that one specific frame data stored in the frame memory in the decoding unit 14 is fixed and continuously provided to the display side (not shown). Thus, the still image can be reproduced on the monitor on the display side.

At this time, if the active signal provided from the control unit 16 to the decoding unit 14 is not synchronized with the frame synchronization signal, in the still picture reproducing mode, the data of two frames is displayed on the monitor in a state in which the two frames are coexisted, so that image quality is maintained. Deterioration is caused. Therefore, the active signal provided from the controller 16 to the decoder 14 must be synchronized with the frame synchronization signal.

On the other hand, even when the control unit 16 stops the restoration operation of the decoder 14 in the still picture reproducing mode as described above, data transfer from the recording medium 10 to the buffer 12 continues. As a result, a full state of data is caused in the buffer 12 to cause loss of data (i.e., discarded data), so that the decoding unit 14 when the still picture playback mode is canceled and switched back to the normal playback mode ) Causes a problem that causes an error.

Therefore, in order to prevent the case caused by data loss due to the data pool state in the buffer 12 as described above, the controller 16 always checks the data full state of the buffer 12 according to the present invention. As soon as a full state of data is generated in the buffer 12, a control signal is provided to the recording medium 10 to stop data transmission from the recording medium 10 to the buffer 12. By doing so, data loss due to overflow of data in the buffer 12 in the still picture reproducing mode is prevented (that is, if data is continuously written to the buffer 12 while the data in the buffer 12 is full, the data are stored. Not stored and overflowed).

Then, when the still picture playback mode is canceled and the system is switched to the normal playback mode, the decoding unit 14 performs the restoration operation of the image data based on the active signal (control signal) from the control unit 16. When the data pool state of the buffer 12 is released, and the data pool state of the buffer 12 is released in this way, the controller 16 stops the image from the buffer 12 to the buffer 12 on the recording medium 10. In the playback mode, a control signal is provided to the recording medium 10 for resuming transmission of the frame data after the stopped frame. At this time, the data transfer from the recording medium 10 to the buffer 12 is substantially buffered in consideration of the fact that the data pool state of the buffer 12 can be continued even in the state of switching from the still picture playback mode to the normal playback mode. The data pool state of (12) is released and then resumed.

Next, in the slow screen reproducing mode, as shown in the example of 1 / 2x speed reproduction at the bottom of FIG. 3, the data restoration operation of the decoding unit 14 is performed based on the active signal from the control unit 16. FIG. The active signal in this case is also synchronized with the frame synchronizing signal as in the still picture reproduction mode described above. That is, in the 1 / 2x playback mode, the decoding unit 14 repeats the restoring operation and stops continuously based on the active signal from the control unit 16, and one frame in the frame memory is executed twice in succession. It is provided on the abbreviated display side, and a 1 / 2x slow screen can be reproduced on the monitor of a display side.

On the other hand, in the case of the fast reproducing mode, the recording medium 10 should read the data in accordance with the mode quickly and the decoding unit 14 should perform the decoding as fast as that, in this case a very fast restoration operation. To achieve this, a decoding apparatus capable of implementing a substantially fast restoration operation is required. This decoding apparatus capable of high speed operation is not only difficult to implement, but even if implemented, the entire system is complicated, resulting in high manufacturing costs. There is a problem.

Accordingly, the present invention proposes a method capable of realizing a high speed playback mode without using a decoding apparatus capable of high speed operation in view of the above points.

That is, as shown in FIG. 4 as an example, in the playback method of the present invention, only certain frame data are selectively reproduced at regular intervals without restoring and reproducing all the frame data in the high speed playback mode, and on the monitor on the output side. Adopt a display technique.

In this case, when specific frames selected according to the present invention have different motion vectors for motion estimation compensation in the transmitting encoder, the motion vectors of the corresponding frames use the frame immediately before the current frame. A frame (a specific frame) is not the one immediately preceding the frame, but a selected frame that is a few frames away from each other becomes a frame immediately before the currently selected specific frame, so that motion compensation is not performed properly and the image itself is broken. In view of this, in the present invention, in the fast playback mode, only a frame having no actual motion vector is selected as a specific frame for fast playback to perform fast playback. Of course, this high speed reproducing operation is performed based on the control signal (active signal) from the control unit 16 based on the high speed reproducing mode signal.

As an example of the fast playback mode as described above, in the MPEG scheme as shown in FIG. 4, the specific frames selected according to the present invention will be I frames and P frames, and B frames having motion vectors are selected. Thus, a skipped frame will be produced. Therefore, the frame I → P → P → I → P → P → I → P → P− is restored and reproduced in the fast playback mode according to the present invention and displayed on the monitor on the display side. These selected specific frames are provided directly to the display side without substantially undergoing motion compensation.

As described above, according to the present invention, during reproduction for display of image data recorded on a recording medium by motion compensation compression encoding, special reproduction, that is, still image reproduction, without complicating the hardware of the entire system for image reproduction , Slow playback or fast playback.

Claims (2)

A digital image reproducing apparatus for reading and reproducing frame data of a motion compensated compressed coded image recorded on a recording medium, the frame data being encoded on the motion frame and stored on the basis of a control signal for reading the stored frame data. A recording medium for providing frame data to be read to its output side, comprising: a buffer for sequentially storing each motion compensated compression coded frame data read out and output to the recording medium at the time of reproduction; Inversely quantize and inverse DCT the quantized DCT transform coefficients obtained by variable length decoding on each of the motion compensated compression-coded frame data provided from the buffer, and then perform motion compensation to the original signal before encoding. A decoder for restoring and providing it to the display side; And provide the reproduction signal for reading the frame data to the recording medium in the normal reproduction mode or the special reproduction mode, and selectively control the data recovery operation of the decoder according to the mode in the special reproduction mode. And a control unit, wherein the control unit temporarily stops the restoration operation of the decoding unit in the stop mode of the special playback mode and simultaneously buffers the buffer from the recording medium based on the data fullness state information provided from the buffer. Control the data transfer to the recording medium, and alternately control the recovery operation and the stop operation of the decoding unit in the low speed mode of the special playback mode, and at the same time to the recording medium based on the data fullness state information provided from the buffer. To control the transfer of data to the buffer, And a read control signal for reading only the specific frame data having no motion vector information on the recording medium so that only the specific frame data can be restored by the decoder in the fast mode. Digital video player A digital image reproducing method of reading frame data of a motion compensated compression-encoded image recorded on a recording medium and reconstructing and reproducing the original signal before being encoded by the decoding means, the digital image reproducing method being recorded on the recording medium in a normal reproduction mode. Reading frame data of the motion compensated compressed coded image and restoring the original signal to the display by the decoding means; Temporarily stopping the restoration operation of the decoding means in the special mode of reproduction and providing only one specific frame data restored to the display side, and at the same time, full data provided from a buffer provided on the output side of the recording medium. Controlling data transfer from the recording medium to the buffer based on status information; By alternately controlling the restoring operation and the stopping operation of the decoding means in the low speed mode of the special reproduction mode, the respective frame data restored during the decompression operation are repeatedly provided to the display side sequentially and provided from the buffer. Controlling data transfer from the recording medium to the buffer based on data fullness information; And the specific frame having no motion vector information among the frame data recorded on the recording medium so that only the specific frame data in the decoding means can be restored and provided to the display side in the high speed mode in the special playback mode. A digital video reproducing method for a special function, comprising: reading only data and providing the data to the decoding means.