Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Reexamination Certificate
2002-05-30
2004-06-08
Edun, Muhammad (Department: 2655)
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
C369S047410, C369S047460, C369S059100
Reexamination Certificate
active
06747927
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to disc drive devices and, more specifically, a device incorporated in a DVD player, a DVD recorder, a personal computer, or the like, and capable of driving discs in DVD format (DVD-ROM discs, DVD-RAM discs, DVD-R discs, DVD-RW discs, etc.) for reading (reproducing) data on a real-time basis, such as video and audio, recorded on the DVD-format discs.
2. Description of the Background Art
As well known, DVD-format discs have such a large storage capacity that they are used mainly for recording and reproducing data on a real-time basis. Data, such as video and audio, that should be recorded and reproduced on a real-time basis is hereinafter called Real-time data. Especially, in writable DVD-format discs, such as DVD-RAM, DVD-R, and DVD-RW discs, a real-time recording (RTR) format is used for recording Real-time data. In the RTR format, Real-time data is compressed with MPEG2 at a compression rate enabling single-speed recording, and then is recorded on a disc. Therefore, the Real-time data recorded in the RTR format (hereinafter, “RTR-format data ”) is generally reproduced at single speed (normal speed) in a disc drive device.
Unlike magnetic tapes, discs (especially, optical discs where data can be recorded or reproduced without any contact) have a feature of enabling a quick change of data locations to be read. Using this feature, one conventional scheme is to read data at a speed equal to or faster than single speed, and then sequentially store the read data in memory of the device before reproduction. In this scheme, if data fails to be read due to a scratch or stain on the disc or vibrations of the device (if a read error occurs), such data can be read again while other data stored in memory is being reproduced. In recent years, technology has been so advanced as to enable CD-ROM drives to carry out data processing at 32× to 48× speeds and DVD-ROM drives to carry out at 8× to 16× speeds.
In general, disc drive devices capable of high-speed reading at single or more speed are also capable of low-speed reading. For example, disc drive devices capable of reading DVD-ROM discs at 8× speed at maximum are often capable of reading at quadruple speed and also at double speed. Note that which speeds are supported by a particular disc drive device depend on its vender.
An example technique using the above feature of supporting a plurality of speeds is disclosed in Japanese Patent No. 2570004, in which the reading speed is varied between Real-time data and program data in order to improve efficiency of reading and executing data that does not have to be read or executed on a real-time basis.
In general, data recorded on a disc is more likely to be successfully read at a low speed, compared with when read at a high speed. Therefore, if an error has occurred during high-speed data reading, the data is generally tried to be re-read at the high speed for several times. If an error still occurs, the data is then tried to be read at the low speed. If a plurality of speeds are supported, the reading speed is changed stepwise within the supported speeds, such as from 8× speed, quadruple speed, double speed, and then to single speed.
Here, if the reading speed is changed to the low speed due to the occurrence of an error, and kept thereat for data reading, data reading has to be carried out always at the low speed even in a case where any further errors will not possibly occur. Such low-speed reading is a waste of time. Therefore, in general, after being changed to the low speed due to the occurrence of an error, the reading speed is returned to the high speed in such a case as after data reading has been carried out for a predetermined number of sectors; after a predetermined time passes; when data reading is carried out for a sector away from the one where the error has occurred, or others.
However, to re-read data after an error has been detected, it takes several tens to hundreds of milliseconds (seek time). Moreover, a process for decelerating or accelerating the reading speed can take several hundreds to thousands of milliseconds at a time. Therefore, such processing time greatly interferes with reproduction of Real-time data, such as RTR-format data. Especially, as for a disc that is error-prone at high-speed reading, if the reading speed is decelerated or accelerated every time when an error occurs with a sufficient amount of data not yet been stored in memory, video and audio recorded on the disc cannot be played back without interruption because data cannot be read during the deceleration or acceleration process.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a disc drive device that optimally controls a speed for reading RTR-format data, such as video and audio, recorded on a DVD-format disc, thereby enabling real-time playback without interruption.
The present invention has the following features to attain the object mentioned above.
A first aspect of the present invention is directed to a disc drive device supporting at least two types of reading speeds, a high speed and a low speed, capable of driving a DVD-format disc, reading data from the disc by following a read instruction from a host section, and sending the read data to the host section. The disc drive device includes: a processing section operable to read, from the disc at one of the reading speeds, the data corresponding to the read instruction and additional information related to the data; a determining section operable to determine, based on the additional information, whether the read data is Real-time data; a storage section operable to temporarily store the read data; and a sending section operable to send the data stored in the storage section to the host section in predetermined playback timing. When the reading speed is currently the low speed, the processing section keeps the reading speed while the determining section determines that the read data is the Real-time data.
Here, when the reading speed is currently the high speed, the processing section changes the reading speed to the low speed when the determining section determines, successively for a predetermined number of times, that the read data is the Real-time data; when a data read error occurs; or after a data read error occurs and then a predetermined condition is satisfied.
At this time, the predetermined condition is preferably whether data reading has been carried out for a predetermined number of times, or for a predetermined period.
Moreover, when the reading speed is currently the low speed, the processing section changes the reading speed to the high speed when the determining section determines that the read data is not the Real-time data and when a predetermined condition is satisfied. Here, when the disc is a DVD-RAM disc and the reading speed is currently the low speed, the processing section may change, under a predetermined condition, the reading speed to the high speed while a reading head is passing through a gap specified in DVD-RAM specifications even though the determining section determines that the read data is the Real-time data.
At this time, the predetermined condition is preferably whether data reading has been successfully carried out for a predetermined number of times or for a predetermined period after a data read error was cleared.
Still further, the additional information is a recording type bit recorded on a header of a sector that stores the data.
As described above, in the first aspect, the information added to the sector is used for determining whether the data is the one recorded on a real-time basis (RTR-format data). When an error occurs at high-speed reading of RTR-format data and therefore the reading speed is changed to the low speed, the reading speed is so controlled as to be kept at the low speed for reading the following RTR-format data. Thus, for RTR-format data, overhead due to repetitive acceleration and deceleration processes can be avoided, and re
Imada Masayuki
Kawasaki Masahiro
Suetomo Toru
Yamamoto Yo-ichi
Edun Muhammad
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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