KR100335060B1 - Apparatus for decoding trick mode and method for the same - Google Patents

Abstract

The present invention relates to a trick mode decoding apparatus and method for slow reverse. In particular, the DSM outputs a video bitstream in units of GOPs, and if a slow reverse playback command is input, repeatedly transmits the same GOP as many times as necessary. The decoder finds the starting point of the transmitted GOP and decodes the M-1 th picture and skips the subsequent pictures. When the M-1 th picture is decoded, the decoder repeatedly repeats the decoding until the M-2 th picture of the sent GOP is decoded. By repeating the process of repeatedly displaying the decoded M-1th picture as a new display frame to the first picture of the same GOP, a low-speed reverse playback display, which is difficult to implement due to the characteristics of the MPEG bitstream, can be implemented.

Description

Apparatus for decoding trick mode and method for the same}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to trick mode decoding of a MPEG (Moving Picture Experts Group) related video decoder, and more particularly, to an apparatus and method for trick mode decoding for slow reverse playback.

In general, when digital storage media (DSM) such as DVD (Digital Versatile Disc), DVCR (Digital Video CassetteRecorder), HDD, etc. are used with MPEG video decoders, various trick playback functions as well as normal playback are required. Shall be.

At this time, typical trick reproduction functions include fast forward (FF), slow forward, fast reverse, slow reverse, and the like.

Here, fast playback, slow playback, fast reverse playback and the like are already implemented and widely used. For example, the fast playback function may be implemented by decoding only an I (Intra-coded) or P (Predicted-coded) picture or a portion of the first half of a group of pictures (GOP). Slow playback is implemented by repeatedly displaying the decoded pictures a suitable number of times. In addition, in case of fast reverse playback, the video decoder behaves like high speed playback, and the DSM reads the GOP backwards.

There are three types of pictures defined in MPEG: I, P, and B pictures. The I picture simply uses DCT and encodes the picture without using motion compensation. In the P picture, motion compensation is performed based on I or another P picture and DCT is performed for the remaining difference. In addition, B (bidirectionally predicted-coded) pictures use motion compensation like P pictures, but unlike P pictures, motion compensation is performed from two frames before and after on the time axis. Therefore, the picture sequence of MPEG-2 has a structure such as ..., B, B, I, B, B, P, B, B, P, B, B, ..., where the display order is referred to. In this case, the G picture from the B picture before the I picture to the P picture before the next I picture is called GOP. On the other hand, the GOP is from the I picture to the next I picture based on the transmission order. Further, when the number of pictures in the GOP is N and the number of pictures between I and P pictures or between P and P pictures is M, N and M values are variable in one sequence.

On the other hand, in the case of the slow reverse playback, the picture must be decoded back to the reverse of one picture and repeatedly displayed, and the picture is reversed in the picture unit as described above due to the characteristics of the MPEG video bitstream which is predictively coded between pictures. Implementation is difficult because it is impossible to decode.

For this reason, currently commercially available DSM-related products do not have slow reverse playback among trick play functions.

Disclosure of Invention The present invention has been made to solve the above problems, and an object of the present invention is to repeatedly decode the same GOP as necessary and display the pictures of the GOP in reverse, so that the trick mode decoding apparatus enables slow reverse playback even in digital storage media. And providing a method.

1 is a block diagram of a digital storage media (DSM) and a video decoder for trick mode decoding according to the present invention.

2 illustrates a slow reverse playback decoding process according to the present invention.

3 (a) to (d) is a view showing a frame memory mapping control process for slow reverse playback decoding and display according to the present invention;

Explanation of symbols for main parts of the drawings

101; Digital storage media (DSM) 102; Video decoder

103: memory

The trick mode decoding apparatus according to the present invention for achieving the above object is a DSM for outputting the video bitstream in a GOP unit, and repeatedly transmitting the same GOP as many times as necessary when a slow reverse playback command is input, the same GOP A video decoding unit configured to repeatedly decode and display the pictures of the GOP in reverse, a plurality of anchor frame memories and at least one B frame memory, frame output necessary for motion compensation of the video decoding unit, storage of video decoded frames, And a storage unit for outputting a frame to be displayed to the video decoder and changing the frame memory mapping according to the type of the picture to be displayed.

In the case of the slow reverse playback decoding, the DSM transmits the video bitstream in reverse in a GOP unit to the video decoder.

The video decoder always decodes the picture to be displayed in the GOP currently being decoded, the previous pictures decode only the I / P picture, the B picture is skipped, and all the pictures thereafter are skipped.

The storage unit fixes the position of the anchor frame memory and the B frame memory while decoding a GOP, and the frame memory in which the picture is stored is only a B frame when the picture to be finally displayed in the GOP is an I / P picture. Memory, changing the frame memory mapping from the remaining memory to the new anchor frame memory.

In the trick mode decoding method according to the present invention, if a low-speed reverse playback command is input when displaying an M (M is a natural number of 1 or more) of a random GOP, repeatedly transmitting the GOP by M-1 times from the DSM. Finds the starting point of the transmitted GOP, decodes it up to the M-1 th picture, and skips subsequent pictures; and when the M-1 th picture is decoded, it repeatedly repeats until the M-2 th picture of the sent GOP is decoded. And repeatedly displaying the decoded M-1 th picture as a new display frame to the first picture of the same GOP.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

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

1 is a block diagram illustrating a DSM and a video decoder according to an embodiment of the present invention, and includes a DSM 101, a video decoder 102, and a memory 103.

The memory 103 is a storage unit, and basically consists of two anchor frames and one B frame memory. This is an example, and the configuration of the memory may vary depending on the designer and the capacity of the memory.

In the present invention, as an embodiment, it is assumed that it is divided into two anchor frame regions and one B frame region. Here, when the video decoder 102 performs motion compensation, a previous reference frame is required. The previous reference frame is an I or P picture, and a memory in which the I or P picture is stored is called an anchor frame memory.

In the present invention configured as described above, when a command such as playback is input, the DSM 101 outputs a video bitstream configured in units of GOP, and the video decoder 102 outputs an overhead (various header information, Start code, etc.), variable length decoding (VLD) of pure data information, and then inverse quantization, inverse discrete cosine transform (IDCT), and motion compensation using motion vectors. Restore the file to the monitor.

In this case, the memory 103 may be divided into output of data required for motion compensation, storage of video decoded data, and output of data to be displayed.

Here, the implementation method of the slow reverse playback decoding is as follows. 2 shows the operation of the slow reverse playback decoding.

First, suppose that a slow reverse playback command is issued when displaying the Mth picture of GOP (0).

Then, the DSM 101 stops continuously transmitting the GOP and repeatedly transmits the current GOP (0) by M-1 times. That is, the DSM 101 repeatedly transmits the same GOP as many times as necessary in the case of the slow reverse playback decoding, and also transmits bitstreams to the video decoder 102 in reverse GOP units.

At this time, the video decoder 102 skips decoding of the remaining pictures already transmitted from the DSM 101, finds the start point of the transmitted GOP (0), and decodes the M-1th picture.

Here, the video decoder 102 decodes only the I / P picture and skips all B pictures except for the M-1 < th > picture. That is, the picture that is displayed (i.e., the M-1th picture of GOP (0)) always decodes regardless of I / P / B, but the previous pictures (i.e., the M-1th previous picture of GOP (0)). Decodes only I / P pictures and skips B pictures. In addition, all subsequent pictures (i.e., after the M-1 th picture of GOP (0)) are skipped.

There are two reasons for this.

First, since the GOP currently decoded needs to display only the M-1th picture, the I / P picture that is absolutely necessary to decode the M-1th picture should be decoded, but the B picture may be skipped. This speeds up the decoding of the M-1th picture and increases efficiency by avoiding unnecessary decoding.

Secondly, since only I / P pictures are decoded, only two anchor frame memories can be decoded until the M-1th picture is decoded, so that the remaining B frame memory can continue to store the previous display frame and repeatedly display while decoding the GOP. Because it can.

When the M-1 th picture is decoded by the above-described process, the decoded M-1 th picture is repeatedly displayed as a new display frame until the M-2 th picture of the GOP (0) which is repeatedly sent is decoded. The rest of the GOP (0) (i.e., the pictures after the M-1 < th >) are skipped. Then, the GOP (0) repeatedly transmitted is decoded in the same manner as the above-described method up to the M- 2nd picture, and then repeatedly displayed as a new display frame. The above process is repeated to display up to the first picture of the same GOP.

Next, the DSM 101 repeatedly transmits the GOP (-1), which is the previous GOP composed of N pictures, N times. The video decoder 102 then displays inversely from the Nth picture to the 1st picture of the GOP (-1) in the same manner as described above.

Repeating the above process results in a slow reverse playback display.

At this time, the GOP is repeatedly decoded to display one picture, but since the slow reverse playback display takes longer to display one picture, and only the I / P picture needs to be decoded and not decoded in accordance with frame synchronization. It can also be implemented.

In addition, the double speed control of the slow reverse playback can be implemented by adjusting the repetitive display time of the display frame.

3 shows a control method of changing the mapping of the frame memory 103 in the video decoder 102 to enable the slow reverse playback decoding and display as described above. That is, while decoding 1 GOP during slow reverse playback, the positions of 2 anchor frame memory (I / P) and B frame memory are fixed, and only when the picture to be finally displayed in the GOP is an I / P picture. The frame mapping in which the picture is stored is changed to B frame memory, and the rest are changed to new two anchor frames. The display always repeatedly displays only the frames of the memory designated as the B frame memory.

For example, assume that the frame memory mapping of the GOP currently being decoded is as shown in FIG. At this time, the display frame of the previous GOP is stored in the B frame memory and displayed repeatedly. The video decoder 102 decodes using two anchor frames.

If the picture to be finally displayed in the current GOP is a P picture and it is stored in the anchor 1 frame memory, when the next GOP is decoded, the anchor 1 frame memory is mapped to a new B frame memory as shown in FIG. Two frame memories (ie, B frame memory and anchor two frame memory) are mapped to new anchor 1,2 frame memories.

Meanwhile, if the picture to be finally displayed in the current GOP is a P picture and it is stored in the anchor 2 frame memory, when the next GOP is decoded, the anchor 2 frame memory is mapped to a new B frame memory as shown in FIG. The remaining two frame memories (ie, B frame memory and anchor 1 frame memory) are mapped to the new anchor 1,2 frame memories.

If the picture to be finally displayed is a B picture, the same frame memory mapping is used in the next GOP decoding as shown in FIG. That is, the position of the anchor frame changes according to the type of the picture decoded last in the current GOP.

The video decoding uses only anchor frames and the display uses only B frame memory while changing the mapping of the frame memory in units of GOPs so that no separate calculation for frame mapping is required.

As described above, only the frame memory mapping is controlled and the video decoder 102 decodes as described above, and if only the B frame memory is repeatedly displayed at all times, a slow reverse playback display is naturally realized.

The present invention effectively implements the slow reverse playback function as described above, so that a complete trick playback function can be provided even in digital storage media.

According to the trick mode decoding apparatus and method according to the present invention as described above, by adding a little control without a significant increase in the performance of the video decoder, it is possible to implement a slow reverse playback decoding that was difficult to implement due to the characteristics of the MPEG bitstream. In this way, it is possible to improve the competitiveness of the product by diversifying the trick reproduction in the system combining the DSM and the video decoder as in the case of the analog.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (8)

A digital storage medium for outputting a video bitstream in units of GOPs, and repeatedly transmitting the same GOP as many times as necessary if a slow reverse playback command is input; A video decoding unit for repeatedly decoding the same GOP and displaying the pictures of the GOP in reverse; And And a plurality of anchor frame memories and at least one B frame memory, and output a frame output necessary for motion compensation of the video decoding unit, a video decoded frame storage, and a frame to be displayed to the video decoder. And a storage unit for changing the frame memory mapping accordingly. The method of claim 1, wherein the digital storage media In the case of slow reverse playback decoding, a trick mode decoding apparatus comprising transmitting a video bitstream in reverse in a GOP unit to the video decoder. The method of claim 1, wherein the video decoder And decoding a picture to be displayed in a GOP currently being decoded, decoding only I / P pictures, skipping B pictures, and skipping pictures afterwards. The method of claim 1, wherein the storage unit While decoding a GOP, the anchor frame memory and the B frame memory are fixed, and the frame memory in which the picture is stored is B frame memory only when the picture to be finally displayed in the GOP is an I / P picture. A trick mode decoding device, characterized by changing the frame memory mapping from the remaining memory to a new anchor frame memory. The method of claim 4, wherein the video decoder Until the decoding of the picture to be displayed is decoded using a plurality of anchor frame memory, the B frame memory repeatedly stores the previous display frame and repeatedly displays only the frames stored in the B frame memory while decoding one GOP. Trick mode decoding device. Claims [1] A trick mode decoding method comprising a digital storage medium for outputting a video bitstream in a GOP unit and a video decoder for decoding a video bitstream transmitted from the digital storage medium. Receiving the GOP repeatedly from the digital storage medium by M-1 times when a slow reverse playback command is input when displaying the M (M is a natural number of 1 or more) picture of an arbitrary GOP; And The starting point of the transmitted GOP is found and decoded to the M-1 th picture, and subsequent pictures are skipped. When the M-1 th picture is decoded, the decoding is repeated until the M-2 th picture of the sent GOP is decoded. And repeating the repeated display of the first M-1 picture as a new display frame to the first picture of the same GOP. 7. The method of claim 6, wherein said decoding and displaying step If the picture to be displayed is the M-1 th picture, the M-1 th picture is decoded unconditionally, the M-1 th previous pictures of the corresponding GOP decode only the I / P picture, and the B picture skips the trick mode. Decoding method. 8. The method of claim 7, wherein said decoding and displaying step If the previous GOP consisting of N pictures is repeatedly transmitted N times from the digital storage medium after the display of the current GOP is performed, decoding is performed in the same manner as described above to reverse from the Nth picture to the first picture of the previous GOP. The trick mode decoding method characterized in that the display.