Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
2002-05-14
2004-03-02
Tran, Thai (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000
Reexamination Certificate
active
06701061
ABSTRACT:
TECHNICAL FIELD
This invention relates to an apparatus for recording digital video images in an endless fashion, and more particularly to an endless video recording apparatus suitable for use to endlessly record digital video images coded using the MPEG which is an international standard of the moving picture coding system.
BACKGROUND ART
Endless recording is known as one of recording methods of video images. The endless recording is a technique of overwriting, after video images are recorded fully into an area on a recording medium which allows recording, new video images on the video data recorded formerly beginning with the top of the recording area again to continuously record an object (video images) incessantly without stopping the recording. Conventionally, in order to realize endless recording of video images (moving pictures), a method is employed wherein analog video images are recorded onto a sequential medium such as a VTR (Video Tape Recorder) or a DV (Digital Video).
However, the sequential medium requires rewinding at a point of time when it is recorded up to the last end, and therefore, it cannot be recorded during the rewinding. Further, since the sequential medium cannot be played back while it is being recorded, in order to play back the sequential medium, recording of the sequential medium must be stopped. Furthermore, since the degree of freedom in accessing of the sequential medium is limited to a one-dimensional one, there is a limitation to the range of applications which can be realized.
Therefore, in recent years, attention is attracted to random access media represented by a magnetic disk or a magneto-optical disk in place of sequential media. A random access medium does not require such rewinding as in the case of sequential media and allows incessant recording. Also it is possible to play back the random access medium while it is being recorded, and besides, the random access medium allows free accessing to any area thereon without any restriction. Due to the characteristics described, where endless recording is executed with a random access medium, not only applications to a monitoring system and so forth which are conventionally used applications but also various applications such as recording and playback of digital video images of general broadcasts can be realized.
Incidentally, thanks to the progress of the coding techniques such as the MPEG-1 and the MPEG-2, digitization of video images and audio sound has advanced rapidly. While the digitization makes it possible to provide a very large amount of information simply and less expensively, simultaneously it is significant in what manner such a very large amount of information should be handled. The endless recording is one of methods for handling such a very large amount of information, and it is considered that the endless recording according to digital video images prevails over conventional analog video images in future.
The endless recording according to digital video images, however, has such subjects to be solved as described below.
Even if analog video images are overwritten on video images recorded in the past by endless recording, since video images in the portion following the overwritten portion remain recorded as they are, video images can be played back in a seamless fashion beginning with any portion of the recording medium. However, digital video images cannot be recorded or played back in a seamless fashion only if they are merely overwritten simply. This is because, although digital video images obtained using a compression technique of the MPEG or the like essentially require information for decoding the video images, there is the possibility that the information may be lost by the overwriting.
In particular, video images are coded and recorded for each predetermined frame unit as shown in
FIG. 28
, and upon such recording, information (header information) for decoding a video image is recorded at the top portion of each coding unit. Taking the MPEG as an example, a GOP (Group of Pictures) which is a coding unit of the MPEG is formed from data of 15 pictures. However, all of the video data do not each form a picture, but only the top data (I data) form one complete picture while each of the following data (P data and B data) represents a difference from the I data. While the MPEG makes it possible to reduce the total amount of information by recording differences from top data in this manner, if the top I data are lost by overwriting by endless recording, then the remaining data (P data and B data) cannot be decoded any more, and upon playback, the played back image is disordered at the portion.
Compression coding systems for digital video images are classified into those wherein the size of a coding unit upon compression is fixed like the compression coding system for the DV and those wherein the size after compression varies for each coding unit depending upon contents of video images to be compressed like the MPEG, and the subject described above is significant particularly in the latter case. In the former case, since the size of a coding unit is fixed, if a recording area is set in accordance with the size of a coding unit, then video images of a coding unit can be overwritten such that they do not span two coding units recorded formerly. However, in video images wherein the magnitude varies for each coding unit as in the MPEG, a coding unit thereof sometimes spans two coding units recorded formerly. In this instance, the header information of a coding unit recorded formerly is lost by overwriting.
The present invention has been made in view of such subjects as described above, and it is a first object of the present invention to provide an endless video recording apparatus which can seamlessly play back digital video images recorded in an endless fashion.
Further, in the conventional endless recording, a fixed area is determined and endless recording is executed within the range of the fixed area. However, since both of the magnetic disk and the magneto-optical disk have a limitation in the recording capacity of the medium, although data which should be recorded preferentially to data which should be recorded endlessly are present, it is sometimes impossible to record the data because the capacity which can be used for recording other than endless recording is small. Also it sometimes occurs conversely that the other area than the endless recording area remains blank without being used. Accordingly, from the point of view of effective utilization of a recording area limited in this manner, preferably the recording range to which endless recording is applied is varied in accordance with the situation.
Therefore, it is a second object of the present invention to provide an endless video recording apparatus which can perform endless recording while varying the recording range for endless recording in accordance with the situation to efficiently utilize the recording area.
Further, in the conventional endless recording, the order in which data are erased by overwriting when endless recording is performed relies upon the time. Therefore, video images which the user principally wants to enjoy are sometimes erased or recorded by endless recording independently of the will of the user.
Therefore, it is a third object of the present invention to provide an endless video recording apparatus which can preferentially leave those data which the user principally wants to enjoy when endless recording is performed.
DISCLOSURE OF THE INVENTION
In order to attain the first object described above, an endless video recording apparatus of an aspect of the present invention is characterized in that it comprises video data recording means for recording video data coded in accordance with the MPEG system for each particular unit formed from at least one or more GOPs (Groups of Pictures) into an endless recording area secured in a recording medium and recording, where video data are recorded fully in the endless recording area, new video data in an overwriting relationship on the video data r
Karasudani Akira
Kato Hideo
Nakano Yasuhiko
Okada Yoshiyuki
Chieu Po-lin
Staas & Halsey , LLP
Tran Thai
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