Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Patent
1995-07-21
1998-02-10
Edun, Muhammad N.
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
369 49, 369 58, 369 59, G11B 700
Patent
active
057176701
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method and apparatus for bit compacting e.g., digital audio signals, a method and apparatus for expanding the compacted information, a method and apparatus for recording/transmitting the compacted information, a recording medium having the compacted information recorded thereon, an apparatus for reproducing the compacted information from a recording medium, and an apparatus for receiving the compacted information. More particularly, it relates to such method and apparatus for changing the time duration of a processing block depending on amplitude changes of an input signal waveform on the time axis.
BACKGROUND ART
The present Assignee has already proposed in e.g., U.S. Pat. No. 5,243,588 a technology of bit compacting input digital audio signals and recording them in a burst fashion on a recording medium with a pre-set data volume as a recording unit.
This technique employs a magneto-optical disc as a recording medium and records adaptive differential (AD) PCM audio data as prescribed in the audio data formats of the CD-interactive (CD-I) or CD-ROM on the magneto-optical disc while reproducing the ADPCM audio data from the magneto-optical disc. The ADPCM audio data are recorded in a burst fashion on the magneto-optical disc with e.g., 32 sectors of the ADPCM audio data and a few linking sectors for an interleaving operation.
As for the ADPCM audio data in the recording/reproducing apparatus employing the magneto-optical disc, several modes can be selected. For example, a level A, having a compaction ratio twice that of the reproducing time for usual compact disc (CD), with the sampling frequency being 37.8 kHz, a level B, having a four-fold compaction ratio, with the sampling frequency being 37.8 kHz, and a level C, having an eight-fold compaction ratio, with the sampling frequency being 18.9 kHz, are prescribed. That is, with the above level B, digital audio data are compacted to approximately one-fourth. The reproducing time or play time of the disc recorded with the level B is four times that of a standard CD format (CD-DA format). This reduces the size of the apparatus because the recording/reproducing time approximately equal to that of a smaller sized disc having a standard diameter of 12 cm can be achieved.
Meanwhile, since the speed of disc rotation of the recording/reproducing apparatus is the same as that of the standard CD, compacted data corresponding to the play time which is four times per unit time can be achieved for the level B. Thus the same compacted data is read four times in redundancy, with the time units of a sector or a cluster, and only one of the four times of reading is routed to audio reproduction. Specifically, track jump is carried out for returning to the original track position for each revolution during scanning or tracking a spirally-shaped recording track, so that the reproduction is carried out in such a manner that the same track is repeatedly tracked four times. Thus it suffices if regular compacted data is produced for at least one of the four times of readout attempts, so that the apparatus is strong against errors caused by disturbances or the like and hence may desirably be applied to a small-sized portable system.
It may also be contemplated to use a semiconductor memory as a recording medium. Specifically, it may be contemplated to record and/or reproduce audio signals using a so-called IC card. Compacted data obtained by bit compaction is recorded or reproduced on or from the IC card. Additional bit compaction is desirably carried out for further improving the compaction efficiency.
The IC card employing a semiconductor memory, for example, is increased in recording capacity or lowered in cost with progress in the semiconductor technology. In an initial stage in which the IC card has started to be offered to the market, it tends to be insufficient in capacity and expensive. Thus it is contemplated to transfer the contents of an other recording medium, which is less expensive and larger in capacity, such as the abov
REFERENCES:
patent: 5587978 (1996-12-01), Endo et al.
patent: 5615187 (1997-03-01), Shinada
IEICE Thesis Journal vol. J71-A, No. 2, Feb. 25, 1988 (25.02.88), Corp. IEICE pp. 443-452.
Edun Muhammad N.
Sony Corporation
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