Television – Camera – system and detail – Combined image signal generator and general image signal...
Reexamination Certificate
1997-12-04
2003-03-25
Vu, Ngoc-Yen (Department: 2612)
Television
Camera, system and detail
Combined image signal generator and general image signal...
C348S231600, C348S231900, C386S349000
Reexamination Certificate
active
06538692
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data storage control method and system, and more particularly to a method and a system which controls writing of image data to a storage medium. The present invention also relates to a data storage system with the above control function.
2. Description of the Related Art
Technology for compressing and coding moving image data and storing it on various types of storage media is evolving. One of typical technology is MPEG. Today, many manufacturers are developing multimedia units and trying to market MPEG-conforming products.
FIG. 1
shows an outline configuration of an MPEG-conforming image recording system with a CCD camera
2
. This image recording system has a compression module
4
, a variable length coding module
6
, and an image recording control system
8
. The compression module
4
performs Discrete Cosine Transformation (hereafter called DCT) on video input data and then quantizes the transformed data. The compression module
4
also compresses data through motion compensation. The variable length coding module
6
uses a probability method to code in the variable length mode the data that has been quantized (hereafter called quantized data) so that the amount of coded data is minimized. The image recording control system
8
has an external medium read/write controller (hereafter called an R/W controller)
10
which controls reading coded of data from and writing of coded data to, an external recording medium
12
.
In this configuration, video signals generated by the CCD camera
2
are sent to the compression module
4
. The compression module
4
disassembles the video signals into discrete space frequency components, one macro block at a time, each macro block being composed of a plurality of picture elements (pixels) of a picture; the module then quantizes the signals into a specified number of levels. The variable length coding module
6
codes the quantized data and generates MPEG coded data streams. An external R/W controller writes the streams on an external recording medium
12
.
When image data is coded into variable length data by the above image recording system, how much image data is recorded in terms of time depends on the type of image data to be recorded (this length of time is referred to as a recording time). The amount of coded data depends on the type of data. Therefore, the recording medium sometimes becomes full before all the image data is recorded, in which case image recording is ended prematurely. This means that, if an image recording system user does not know a recording time, he or she has sometimes image recording interrupted and therefore cannot record all desired image data successfully.
No efficient method has been developed for predicting how long a user may continue recording on a current medium. Even if the user can predict the remaining recording time of the current medium, the actual recording time depends on some other factors such as the type of image data which will be recorded. Even when the predicted remaining recording time is shorter than the actual recording time, it is desirable that recording be continued without interruption.
Another solution is to extend a recording time by controlling the amount of code. A disadvantage to this solution is that a less amount of code degrades the quality of decoded image data.
The above problem is not limited to image data recording. The problem also applies when other types of data, such as voice data, are recorded on an external storage medium.
SUMMARY OF THE INVENTION
The present invention seeks to solve the problems associated with a prior art described above. It is an object of the present invention to provide a data storage control method and system that prevent a situation in which recording is interrupted because an external medium becomes full before all intended data is recorded. It is another object of the present invention to provide a data storage system with the function described above.
(1) A data storage control method according to the present invention is a method for controlling storage of data on a removable external recording medium which can be installed on a storage system, comprising the steps of stopping storing data on the external recording medium when judgment is made not to store data on the external recording medium and, at the same time, storing data, which follows data stored on the external recording medium, in an internal storage means.
Preferably, data to be processed by this method is image data, voice data, and so forth. As will be described later, the method according to the present invention is applicable to the recording of still image data and moving image data. An external recording medium, a unit separate from an image recording system, may be exchanged as necessary. This external recording medium may be an IC card, floppy disk, CD-ROM, or magnetic tape, or the like. The external recording medium is an electrically-, magnetically-, or optically-accessible medium. So is the internal storage mean; a semiconductor memory is used as necessary.
For example, judgment “not to store data on the external recording medium” may be made when the amount of data on the external recording medium has reached a predetermined amount. The predetermined amount should preferably be set to the size of the data storage area on the external recording medium or to a value close to it.
When judgment is made in this configuration that no more data should be stored on the external recording medium, data which follows data stored on the external recording medium is held in the internal storage means to allow all desired data to be recorded without interruption.
While data is being stored on the external recording medium in the system according to the present invention (that is, during usual recording time), one of the following two types of processing may be performed on the internal storage means. During usual recording time, (A) data is not stored in the internal storage means, and (B) data is stored and updated in the internal storage means.
A method according to the present invention in which (A) described above is performed is a method for controlling storage of data which comprises steps of comparing an amount of free space on the external recording medium with an amount of data to be stored next; storing data on the external recording medium if the amount of free space is larger than the amount of data; and storing data in the internal storage means if the amount of free space is insufficient. After the data destination is changed, data is stored in the internal storage means. In this case, the time when “the free space is insufficient” corresponds to the time when “judgment is made that no more data should be stored on the external recording medium which is separate from the system” described above.
For example, the amount of image data coded into variable length data is variable. Therefore, in the above configuration, the comparison between amount of data to be stored next with the amount of free space depends on the amount of data.
A method according to the present invention in which (B) described above is performed is a method for controlling storage of data, wherein data in the internal storage means is updated by sequentially-entered data and wherein, when the amount of data stored on the external recording medium has reached a predetermined amount, data which follows data stored on the external recording medium is held in the internal storage means.
The time “when the amount of data stored on the external recording medium has reached a predetermined amount” corresponds to the time when “judgment is made that no more data should be stored on the external recording medium” described above. In this case, the “predetermined amount” may be the maximum size of the space available for storing desired data or an amount smaller than but close to the maximum. As described above, a module for comparing the amount of free space with the amount of data to be stored next may be adde
Hogan & Hartson LLP
Sanyo Electric Co,. Ltd.
Vu Ngoc-Yen
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