Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1999-09-07
2004-12-21
Tran, Thai (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000
Reexamination Certificate
active
06834155
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image regeneration device and an image regeneration method for regenerating image data of frames of a moving picture from code data which have been compressed according to a standard such as MPEG and stored in a record medium such as a CDROM, and in particular, to an image regeneration device and an image regeneration method in which a predetermined frame of the moving picture is displayed as a still image in the display of the moving picture.
DESCRIPTION OF THE PRIOR ART
In recent years, standardization has proceeded in techniques for digitally compressing moving pictures and still images. Among such standards is the standard by MPEG (Moving Pictures Expert Group).
FIG. 1
is a schematic diagram showing an example of the relationship between the image regeneration order and the display order of frames, in the case where code data (coded data) of the frames which has been compressed according to MPEG are regenerated (decoded) into image data of the frames and the frames are displayed. The I-frame (Intra-coded picture frame: the frame I
1
) shown in
FIG. 1
is a frame which can be regenerated by use of its own code data only. The P-frame (Predictive-coded picture frame: the frame P
4
or P
7
) shown in
FIG. 1
is a frame which is regenerated by use of its own code data and by means of prediction referring to an I-frame or a P-frame of the past. The B-frame (Bidirectionally predictive-coded picture frame: the frame B
2
, B
3
, B
5
or B
6
) shown in
FIG. 1
is a frame which is regenerated by use of its own code data and by means of bidirectional prediction referring to an I-frame and/or a P-frame of the past and/or the future.
An example of the regeneration of the P-frames and the B-frames referring to other frames will hereafter be explained referring to FIG.
1
. The frame P
4
shown in
FIG. 1
is a frame to be regenerated by means of prediction referring to the frame I
1
. The frame B
2
is a frame to be regenerated by means of prediction referring to the frames I
1
and P
4
. The frame B
3
is also a frame to be regenerated by means of prediction referring to the frames I
1
and P
4
. The display order (i.e. the order of display of the frames) is I
1
, B
2
, B
3
, P
4
, B
5
, B
6
, P
7
, . . . . However, the frames B
2
and B
3
have to be regenerated by means of the prediction using the future frame P
4
, and thus the frame P
4
has to be regenerated before the frames B
2
and B
3
. In the same way, the frames B
5
and B
6
have to be regenerated by means of the prediction using the future frame P
7
, and thus the frame P
7
has to be regenerated before the frames B
5
and B
6
. Therefore, the image regeneration order (i.e. the order of regeneration of the frames) becomes I
1
, P
4
, B
2
, B
3
, P
7
, B
5
, B
6
, . . . .
FIG. 2
is a graph showing the time-variation of the amount of code data of frames which are stored in a buffer circuit of an image regeneration device. The horizontal-axis of the graph indicates image regeneration of each frame. Compressing/regenerating method according to MPEG varies depending on the types of frames. As shown in
FIG. 2
, I-frames consume a large amount of code data (i.e. decrease the amount of code data stored in the buffer circuit) when regenerated, since the I-frame is regenerated by use of its own code data only and thus a large amount of its own code data is consumed. On the other hand, B-frames tend to store code data (i.e. increase the amount of code data stored in the buffer circuit) when regenerated, since the B-frame is regenerated by means of bidirectional prediction referring to image data of an I-frame and/or a P-frame of the past and/or the future and thus a little amount of its own code data is consumed.
As mentioned above, the amount of code data consumption in the buffers-circuit varies depending on the types of the regenerated frames, while data transfer rate between a record medium (CDROM etc.) and the buffer circuit is fixed. Therefore, in order to read out MPEG code data from the record medium at a constant data transfer rate and execute the image regeneration process smoothly, the buffer circuit for temporarily storing the MPEG code data of frames becomes necessary for avoiding overflow or underflow of the MPEG code data. For example, in cases where the underflow occurred and the buffer circuit became empty, the image regeneration process has to be suspended, and thereby the continuity or smoothness of display of the moving picture is necessitated to be deteriorated. Therefore, in order to avoid such troubles, the image regeneration process for the frames of the moving picture ought to be started after a certain amount of data has preliminarily been stored in the buffer circuit. In MPEG, the amount of code data which should be stored in the buffer circuit before the start of the regeneration process for the first frame is designated in “VBV delay” in the picture layer.
There have been established some standards for techniques for compressing moving picture data according to MPEG or CDROM-XA (Compact Disc Read Only Memory Extent Architecture) and storing the compressed data in sectors of a CD (Compact Disc). The video CD standard is one of such standards. In the video CD standard, an “automatic pause function” has been defined. In the automatic pause function, if an automatic pause trigger bit of a sector has been turned on, a frame corresponding to the sector keeps on being displayed by a display device as a still image until the automatic pause is released by the user.
FIG. 3
is a schematic diagram showing the structure of a sector of a CDROM according to CDROM-XA Form 2. As shown in
FIG. 3
, compressed code data corresponding to a frame is stored in one or more sectors of the CDROM. In
FIG. 3
, the automatic pause trigger bit with respect to a frame is placed in the sub-mode area in the sub-header of one of the sectors corresponding to the frame. Generally, compressed code data of a frame is distributed to a plurality of sectors and stored in user data areas of the sectors.
A technique which has been disclosed in Japanese Patent Application Laid-Open No. HEI7-226903 is known as a method for implementing the automatic pause function.
FIG. 4
is a schematic block diagram showing the composition of an image regeneration control device which has been disclosed in the document. The image regeneration control device of
FIG. 4
includes a reading circuit
32
, a buffer circuit
33
, a regeneration circuit
34
and a display circuit
35
. The record medium
31
shown in
FIG. 4
has a plurality of memory areas corresponding to sectors, and each of the sectors is provided with the sub-mode area and the user data area. The reading circuit
32
reads out code data which have been stored in the user data areas of the sectors of the record medium
31
, and writes the code data in the buffer circuit
33
. The buffer circuit
33
temporarily stores the code data written by the reading circuit
32
. The regeneration circuit
34
reads out the code data from the buffer circuit
33
, regenerates image data from the code data, and sends the image data to the display circuit
35
. The display circuit
35
displays the image data supplied from the regeneration circuit
34
.
In the record medium
31
, code data necessary for the image regeneration is distributed to a plurality of sectors and stored in the user data areas of the sectors as has been shown in FIG.
3
. If there is a frame to be displayed as a still image (i.e. a frame to be displayed according to the automatic pause function), the automatic pause trigger bit of the sub-mode area of the last sector corresponding to the frame (i.e. the last one of the sectors in which the code data of the frame is distributed and stored) is turned on.
The reading circuit
32
executes the reading of the code data from the record medium
31
successively in units of sectors, and sends the code data corresponding to each sector to the buffer circuit
33
.
FIG. 5
is a flow chart showing the reading operation of the read
McGinn & Gibb PLLC
NEC Electronics Corporation
Tran Thai
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