Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1999-09-07
2004-09-14
Nguyen, Huy (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000, C386S349000
Reexamination Certificate
active
06792196
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for reproducing a video signal and, more particularly, to a reproduction method and a reproduction apparatus for reproducing past image data of coded data using a MPEG coding method.
BACKGROUND OF THE INVENTION
In the MPEG coding method, video signals are coded by three coding methods of an intra frame coding (I, Intra Picture), a forward prediction coding (P, Prediction picture), and a bidirectional prediction coding (B, Bidirection picture). It is already known that pictures from an Intra Picture to the next Intra Picture constitute one GOP (Group of Picture) unit.
Conventionally, when data is reproduced using the MPEG coding method, the data is generally reproduced in GOP units. Accordingly, in reproducing from a storage type recording medium, such as an optical disk, when a frame which has been displayed previously to a frame displayed presently should be displayed again, that is, when reverse reproduction should be performed, a coded data stream previous to the presently displayed frame is reproduced again from a head of a GOP including the data stream from a coded data generating unit, to decode and display the frame.
FIG. 5
is a block diagram illustrating a prior art reproduction apparatus.
In the figure, reference numeral
5
designates an optical disk on which video signals are recorded. Numeral
6
designates a reproduction head for reading out data which is stored on the optical disk
5
. Numeral
7
designates a reproduction circuit for reproducing the data read out by the reproduction head
6
. Numeral
1
designates a first memory for temporarily storing the data of the reproduction circuit
7
. Numeral
8
designates a decoder circuit for reading out and decoding the data stored in the first memory
1
. Numeral
2
designates a second memory for temporarily storing data decoded by the decoder circuit
8
. Numeral
9
designates an output circuit for outputting the data stored in the second memory
2
, as a video signal.
An operation of the thus constructed reproduction apparatus will be described with reference to FIG.
5
.
Initially, video signals are coded by the three coding methods of the intra frame coding (I), the forward prediction coding (P), and the bidirectional prediction coding (B). Then, a GOP is constituted by pictures in a cycle of the intra frame coding (I), and coded data which is coded in a variable bit rate, with a data amount of each GOP varying with images, is recorded on a storage type recording, medium, such as the optical disk
5
.
The coded data recorded on the optical disk
5
is read out by the reproduction head
6
, a coded data stream is obtained by the reproduction circuit
7
, and the coded data stream is temporarily stored in the first memory
1
. The decoder circuit
8
reads out the data from the first memory
1
and decodes the readout data to generate a decoded signal. The decoded signal generated by the decoder circuit
8
is output by the output circuit
9
as a video signal, through the second memory
2
, and sent to a terminal
12
.
Here, since the coded data streams are coded in the variable bit rate, the coded data streams are reproduced intermittently from the optical disk
5
. That is, the coded data streams are temporarily buffered by the first memory
1
, and thereafter read out in response to a request from the decoder circuit
8
. The first memory
1
is indispensable for performing this buffering.
Here, the decoded signal generated by the decoder circuit
8
can be directly output to the output circuit
9
without passing through the second memory
2
. This operation is already used in products, such as a DVD player, and widely known.
As described above, in the prior art reproduction method and reproduction apparatus, coded data streams which are not decoded or displayed yet, i.e., coded data streams of frames to be displayed in the future, are stored in the first memory
1
, and past coded data streams which have been displayed previously to an image which is displayed at present are not stored anywhere. Therefore, when operations such as an inverse reproduction, a reverse reproduction, a rewind reproduction, or reproduction of a past designated frame, for again displaying a past frame previous to the presently displayed frame should be performed, the first frame of a GOP including a coded data stream of a frame to be displayed is read out again, reproduced and decoded.
Next, an operating method for displaying past frames again will be described with reference to FIG.
3
.
FIG. 3
is a diagram schematically illustrating a data arrangement of coded data streams on a track of an optical disk. Each GOP usually comprises about
15
frames of data. The first frame of each GOP is coded by the intra frame coding (I). In addition, frames other than the first frame are coded by the forward prediction coding (P) or the bidirectional prediction coding (B).
In the figure, image signal data stored on the optical disk
5
is coded in order of GOP
1
, GOP
2
, GOP
3
, and GOP
4
. It is assumed that a frame A is displayed at present and then, a frame B which is a past frame displayed previously to the frame A should be displayed. Here, the frame B is included in GOP
4
. The frame B can be coded by either the forward prediction coding (P) or the bidirectional prediction coding (B). Further, the frame B can be a frame which is adjacent to the frame A or a frame which is not adjacent to the frame A.
Conventionally, in order to decode and display the frame B which is past data, the first frame of a GOP including the frame B from the optical disk
5
should be detected, and then the frame B is decoded again. That is, in order to display the frame B in
FIG. 3
, a frame
14
is detected and then data of the frame
14
is read out from the optical disk
5
again by using the reproduction head
6
.
However, in this prior art reproduction method and apparatus, in order to display the frame B as the past data, a seek time for the reproduction head
6
to detect the frame
14
, a time for sending the data to the reproduction circuit
7
and further, though the first memory
1
, to the decoder circuit
8
, and a time for decoding frames of from
14
to B are required, whereby it takes quite a long time. Particularly, the seek time for the reproduction head
6
to detect the frame
14
is quite long, due to a delay time by the reproduction apparatus.
Further, when a coded data generating unit is an optical disk, a time for reproducing data again from the optical disk is additionally required, whereby it takes an increased amount of time to decode and display the data. Further, when the coded data generating unit is a device for receiving broadcasting, such as satellite broadcasting, past image data cannot be reproduced.
SUMMARY OF THE INVENTION
The present invention is made to solve the above-mentioned problems, and it is an object of the present invention to provide a reproduction method and a reproduction apparatus, which can store past coded data streams which are previous to a frame displayed at present or past decoded image data in a storage, and read out the stored data when the past image data should be displayed, thereby considerably reducing the time required to display the past image data.
Other objects and advantages of the present invention will become apparent from the detailed description and specific embodiments described are provided only for illustration, since various additions and modifications within the spirit and scope of the invention will be apparent to those of skill in the art from the detailed description.
According to a first aspect of the present invention, a reproduction method for reading out coded data which is obtained by coding video signals by three coding methods of an intra frame coding (I), a forward prediction coding (P), and a bidirectional prediction coding (B), the coded data constituting a GOP in a cycle of the intra frame coding, and being coded in a variable bit rate with a data amount of each GOP varying with image
Nguyen Huy
Wenderoth , Lind & Ponack, L.L.P.
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