Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1998-03-18
2001-05-22
Vu, Huy D. (Department: 2739)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C345S504000
Reexamination Certificate
active
06236663
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to an information reproduction apparatus and an information reproduction method for reading out and reproducing information material having a plurality of clips.
2. Description of the Related Art
In recent years, the techniques of compression-coding image information and audio information with minimum deterioration and then decoding the compressed-coded information material with a reproducing means have been developed. For example, the MPEG (Motion Picture Experts Group) system standard has been proposed as a scheme for compression-coding and then decoding (expanding) image information and audio information. An audio-video material or the like that has been compressed and multiplexed according to the MPEG system standard consists of a plurality of clips as shown in FIG.
10
. Each clip consists of a plurality of clusters, four clusters in the example of
FIG. 10. A
“cluster” is a unit that is an integral multiple of a unit (for instance, 512 bytes) that is formed on a hard disk and generally called a sector. The example of
FIG. 10
shows two clips, i.e., a certain clip CP
2
and a preceding clip CP
1
.
In the conventional example of
FIG. 10
, information material (MPEG stream)
2
having clips CP
1
, CP
2
, etc. is recorded on a hard disk (HDD)
1
. The information material
2
recorded on the hard disk
1
is to be decoded by a decoder. However, direct access to the information material
2
cannot be effected between the hard disk
1
and the decoder
2
. This is because the MPEG stream is recorded on the hard disk
1
so as to be divided into certain units (for example, 4-byte units; hereinafter referred to as cells
1
a
) and a DMA buffer
3
needs to be used as a buffer for absorbing a size difference between the cell
1
a
of the hard disk
1
and the cluster CT. That is, in accessing the hard disk
1
, the information material
2
needs to be temporarily stored in a buffer
3
A or a buffer
3
B.
To decode the clusters of the clips CP
1
and CP
2
, for instance, by sending them to decoders
4
a
and
4
b
consecutively, a switcher
5
is used as shown in FIG.
10
. The first cluster CT
1
of the preceding CP
1
is stored in the buffer
3
A and reproduced by a decoder
4
a,
and the next cluster CT
2
is stored in the buffer
3
B and decoded by the decoder
4
b.
The switcher
5
sequentially outputs the clusters CT as a video signal, an audio signal, or the like by switching between the decoders
4
a
and
4
b.
As the switcher
5
switches between the decoders
4
a
and
4
b,
the clusters CT of the preceding clip CP
1
and the clusters CT of the (ensuing) clip CP
2
are reproduced consecutively.
When a user reproduces and uses audio-video material with a VTR or the like, he may want to start reproduction of a clip of the audio-video material from a certain position thereof as well as from its beginning. For this purpose, equipment such as a VTR is generally provided with such functions as FF (fast forward) and REW (fast reverse).
With equipment such as a VTR, when a user uses a system for decoding (reproducing) an audio-video material that has been coded according to the MPEG system scheme, he may want to start reproduction of a clip of a decoded audio-video material from a certain position thereof This operation can be realized by the following two methods:
Method A: Encoding a clip so that certain codes to serve as “markers” are inserted everywhere in the clip, and supporting a function that enables reading a clip of data to be started from a desired marker position in reproducing the clip.
Method B: Calculating a reproduction start position based on the compression rate of a clip and a desired time point (position). According to this scheme, for example, if the compression rate is 10 Mbps and it is desired to start reproduction from a time point 120 seconds after the present time, reproduction may be started from a position 1,200 Mbits downstream of the present position.
The above-described method A is employed in the DVD (digital versatile disc) etc. Although this method has the advantage that reproduction can be started precisely from a desired position, a function for handling “markers” is necessary, resulting in the disadvantage that the system configuration becomes more complex.
On the other hand, method B has the advantage that the system remains simple because it can be implemented easily, though it has the disadvantage that reproduction can be started only from an approximate position. However, there are a considerable number of uses in which reproduction need not always be started from a precisely determined position, that is, an accuracy of about several seconds is allowable. An example of such uses is the case that a user wants to reproduce a clip again from a somewhat upstream position. Method B is most appropriate for such common uses.
However, in method B, if reproduction is started from an arbitrary position, that is, if no limitation is imposed on the reproduction start position, there may occur a case that reproduction (i.e., an operation in which a clip of a coded audio-video material is supplied to a decoder and decoded there) is started from a certain position of a minimum unit called a “packet” that is prescribed by the MPEG2 system standard. In this case, the decoder may not be able to process the data correctly.
An object of the present invention is therefore to solve the above problems of method B and to thereby provide an information reproduction apparatus and an information reproduction method which can perform special reproducing operations such as fast forward and fast reverse on an audio-video material in a precise manner.
SUMMARY OF THE INVENTION
According to the invention, the above object is attained by an information reproduction apparatus for reading out and reproducing information material having a plurality of clips, comprising recording media on which the information material is recorded in minimum accessible units, information material storing means, including temporary buffer means, for reading out from the recording media, upon request and in sequence, a first clip and a second clip of the information material that each consist of a plurality of recording media access units, and writing the readout clips to the temporary buffer means, information material reproducing means for reproducing in process units the first clip from the temporary buffer means at the same time that the second clip is being written in the temporary buffer means by the information material storing means, and wherein a size of the recording media access unit is set at a common multiple of a size of the recording media minimum accessible unit and a size of a minimum process unit in the information material reproducing means.
In the preferred embodiment, the information material of the recording media is audio-video information that has been compression-coded, and the information material reproducing means decodes the information material. The recording media are preferably magnetic or magneto-optical disks and the size of the recording media minimum accessible unit is a sector size and the minimum process unit in the information material reproducing means is a packet size. The minimum process unit in the information material reproducing means is either a transport stream packet of, for example, 188 bytes, or a program stream packet of, for example, 2,048 bytes. The recording media access unit is a cluster size of, for example, 128 packets or 384 packets.
The object of the invention is also attained by an information reproduction method for reading out and reproducing information material having a plurality of clips, comprising the steps of recording the information material on recording media in minimum accessible units, reading out from the recording media, upon request and in sequence, a first clip and a second clip of the information material that each consist of a plurality of recording media access units, and writing the readout clips to a temporary buffer
Shaw, Jr. Philip M.
Sony Corporation
Vu Huy D.
LandOfFree
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