Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1999-11-12
2004-03-30
Boccio, Vincent (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000, C386S349000, C386S349000, C714S710000, C360S077040
Reexamination Certificate
active
06714719
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to magnetic disk drives that read and write data on magnetic disks in response to commands given from host systems. Particularly, this invention relates to video recording/reproduction systems that use the magnetic disk drives to perform video recording and reproduction under control of the host systems.
This application is based on Patent Application No. Hei 10-322666 filed in Japan, the content of which is incorporated herein by reference.
2. Description of the Related Art
A variety of papers disclose the technologies regarding the magnetic disk drives and video recording/reproduction systems, as follows:
For example, Japanese Patent Application, First Publication No. Hei 10-49312 discloses a magnetic disk drive, which uses a nonvolatile memory to speed up the processing, regarding recording and reproduction of data on magnetic recording media, by eliminating an access time for an access to an alternative sector address which is physically discontinuous.
Japanese Patent Application, First Publication No. Hei 7-307061 discloses a recording and reproducing device, which is designed to reduce recording time and reproducing time even if a disk contains a defective sector by accessing its alternative sector within a solid memory.
Japanese Patent Application, First Publication No. Hei 8-76933 discloses an example of a format operation controller, in which an alternative sector process and/or defective sector mapping is performed with respect to a defective sector detected on a new hard disk to record picture data.
In the magnetic disk drives, magnetic heads perform magnetization on magnetic layers corresponding to surfaces of magnetic disks, which rotate at high speed. Thus, the magnetic disk drives are capable of recording and reproducing desired data on the magnetic disks. Normally, the magnetic heads fly over the magnetic disks, which rotate at high speed, by some gaps to read and write data without making contact with the disk surfaces. Recently, the gaps by which the magnetic heads fly over the rotating magnetic disks are reduced to cope with increases in capacities and recording densities of the magnetic disk drives. Such reduction of the gaps makes the magnetic heads to easily come in contact with the disk surfaces. When magnetoresistance effect components are used for reproduction heads, disturbances are introduced into reproduction waveforms due to so-called “thermal asperity”, which correspond to rapid temperature variations of the components being caused by contacts between the heads and disks. For this reason, it is required to reduce roughness of the disk surfaces and disturbance (or partial defectiveness) of the magnetic layers more strictly.
However, it is almost impossible to perfectly eliminate defects of the disks in manufacture. So, manufacturers make the magnetic disk drives in consideration of the defects of the disks to some extent. In order to use the disks having such defects without troubles, the magnetic disk drives are generally designed to effect defect repair processes, which are called “reassignment processes (or alternate processes)”, when detecting defects of the disks. According to the reassignment process, the magnetic disk drive recognizes an area (i.e., sector), on which a recording/reproduction process cannot be performed normally due to existence of a defect, as a defect sector. Specifically, the magnetic disk drive stops using such a defect sector by recording data representative of existence of the defect in a header portion (i.e., ID portion) of the defect sector. Herein, an alternate sector region is prepared in advance for replacement of the defect sector on a same track of the defect sector or within a zone containing the defect sector. From such an alternate sector region, the magnetic disk drive determines and assigns an alternate destination sector. In addition, the magnetic disk drive stores information representative of a location of the defect sector to the magnetic disk or a prescribed memory provided inside thereof. Thus, the magnetic disk drive controls such that access to the defect sector is changed over to access to the alternate destination sector of the alternate sector region.
Enlargement of capacities of the magnetic disk drives is achieved mainly by reduction of record bit lengths as well as by increase of record track densities. High track densities inevitably require servo control techniques for accurate positioning of heads on desired track positions. Particularly, in order to cope with environmental variations in temperature and humidity as well as mechanical variations when the magnetic disk drives operate for a long time, it is necessary to perform calibration of servo control system every prescribed time with respect to the magnetic disks of high track densities. There are provided a variety of examples for the calibration, as follows:
i) Circuit/HDA calibration for performing corrections specifically with respect to circuit boards and head disk assembly (HDA);
ii) Calibration (head sensitivity correction) for accuracy of positional error signals;
iii) Disk eccentric calibration;
iv) Calibration (current/acceleration reduced gain) for voice coil motor (VCM) control system that drives a head arm to move to a predetermined position; and
v) Calibration for external forces such as wind pressure being applied to the head arm or flexible printed-circuit board (FPC).
The aforementioned reassignment process and calibration process are performed in factory shipment inspection, which is made just before shipment of products corresponding to the magnetic disk drives, or when the users start to operate the magnetic disk drives. As for the circuit/HDA calibration, data are measured in the factory shipment inspection and are recorded on a memory such as a ROM provided in the magnetic disk drive. Such data can be used for corrections of the magnetic disk drive after the shipment. In contrast, the reassignment process is effected with respect to the defect sector which occurs after the shipment, while time-related variations (e.g., temperature variations) may be included in the disk eccentric calibration and VCM control system calibration after the shipment. So, they must be performed after the shipment or when the user starts to operate the magnetic disk drive.
Video recording/reproduction systems conventionally use the aforementioned magnetic disk drives for recording and reproduction of video information on the magnetic disks. However, the conventional video recording/reproduction system using the magnetic disk drive suffers from a variety of problems as follows:
i) A first problem is that the system badly records and reproduces video images which may be interrupted intermittently due to the reassignment process and calibration, so the magnetic disk drive is damaged in reliability while picture quality of display is damaged. Because, when the reassignment process is performed due to occurrence of the defect sector in the magnetic disk storing the video data having continuity or when the calibration is performed at certain intervals of time while the magnetic disk drive is operating to read or write video data having continuity, such continuity of the video data must be interrupted (intermittently).
ii) A second problem is that when the user starts video recording at an arbitrary time, the video recording cannot be started instantaneously, so some part of vido images must be broken without being recorded on the disk. Because, in some cases, the magnetic disk drive performs the calibration at the timing when the host machine issues a record start instruction. At that time, the magnetic disk drive is occupied in calibration, so the system cannot execute the record start instruction immediately.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a video recording/reproduction system using a magnetic disk drive, which is improved in reliability by controlling a reassignment process and calibration in such a way that recording and reprodu
Boccio Vincent
NEC Corporation
Young & Thompson
LandOfFree
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