Dynamic information storage or retrieval – Information location or remote operator actuated control – Selective addressing of storage medium
Reexamination Certificate
1999-07-26
2001-11-20
Dinh, Tan (Department: 2651)
Dynamic information storage or retrieval
Information location or remote operator actuated control
Selective addressing of storage medium
Reexamination Certificate
active
06320825
ABSTRACT:
FIELD OF THE INVENTION
The invention is related to the field of recording variable bitrate compressed digital audio signals.
BACKGROUND OF THE INVENTION
The invention relates to a method for recording audio information on a record carrier, the method comprising the steps of encoding the audio information to compressed audio data having a variable bitrate, recording the compressed audio data at a transfer speed, and controlling the transfer speed in dependence on the variable bitrate.
The invention further relates to a device for recording audio information on a record carrier, the device comprising compression means for encoding the audio information to compressed audio data having a variable bitrate, recording means for recording the compressed audio data at a transfer speed, and a control unit for controlling the transfer speed in dependence on the variable bitrate.
The invention further relates to a record carrier carrying audio information, which audio information is encoded to compressed audio data having a variable bitrate, and transfer speed information for controlling a transfer speed at playback.
The invention further relates to a playback device for retrieving audio information from the record carrier, the device comprising reading means for retrieving the compressed audio data at a transfer speed, and a control unit for controlling the transfer speed.
Such a method and apparatus are known from Research Disclosure 36411, document D1 in the list of related documents. The document discloses a system for variable speed recording of audio information on a record carrier, in particular speech on a magnetic tape. Compression of the audio information is used to minimize tape consumption and realize a high effective audio information density, i.e. the amount of audio information per unit of record carrier surface. When data is recorded on the tape at a constant spatial data density the data transfer speed is proportional to the tape transport speed. The known recording apparatus comprises an audio compressor for encoding the audio information to digital audio data having a variable bitrate. A channel encoder formats the compressed audio data and passes the data to a recording head via a smoothing buffer. The actual bitrate of the compressed audio data at the output of the audio compressor is measured by a bitrate determining means, which means controls the tape transport speed in dependence on the actual bitrate. The buffer is kept half full during normal operation and will absorb sudden changes in the actual bitrate, while the tape transport speed can be adapted according to the data rate changes at the output of the smoothing buffer. A speed control signal, indicating the actual tape transport speed at the moment of recording, may be recorded on the record carrier, e.g. a clock signal in a separate track of the tape. An optical disc is mentioned as record carrier in a further embodiment, which embodiment comprises a buffer sufficiently large to store the data recordable in one winding of the track. Recording is performed for one complete revolution of the disk and then halted until the buffer again contains sufficient data. The average data transfer speed of the disc is controlled by jumping back, i.e. moving the head to the previous track when recording is halted, while the transport speed of the disc relative to the recording head, called the linear speed, is not changed. Those skilled in the art are directed to the following related documents:
(D1) Research Disclosure number 36411. August 1994, page 412-413
(D2) PCT/IB97/01156 (PHN 16.452) 1 bit ADC and lossless compression of audio
(D3) PCT/IB97/01303 (PHN 16.405) Audio compressor
(D4) EP-A 402,973 (PHN 13.241) Audio compression
(D5) 'A digital decimating filter for analog-to-digital conversion of hi-fi audio signals', by J. J. van der Kam in Philips Tech. Rev. 42, no. 6/7, April 1986, pp. 230-8
(D6) 'A higher order topology for interpolative modulators for oversampling A/D converters', by Kirk C. H. Chao et al in IEEE Trans. on Circuits and Systems, Vol 37, no. 3, March 1990, pp. 309-18.
The above citations are hereby incorporated in whole by reference.
SUMMARY OF THE INVENTION
The known recording apparatus and record carrier have the problem, that changing the data transfer speed by controlling the transport speed and/or moving the head requires complex control means and relatively powerful servo motors, while frequent transport speed changes and/or head movements cause excessive wear.
It is an object of the invention to provide means for transferring audio information via a record carrier in a less complex way, while realizing a high effective information density.
For this purpose a method as described in the opening paragraph is characterized according to the invention in that the method comprises the steps of determining a transfer speed profile for an item of audio information in which profile the average transfer speed is higher than an average transfer speed minimally required to transfer the compressed audio data of said item, adding stuffing data to the compressed audio data according to the transfer speed profile, and recording transfer speed profile information on the record carrier for enabling playback at a transfer speed as indicated by the transfer speed profile information.
For this purpose a recording device as described in the opening paragraph is characterized according to the invention in that the control unit is arranged for determining a transfer speed profile for an item of audio information in which profile the average transfer speed is higher than an average transfer speed minimally required to transfer the compressed audio data of said item, and in that the device comprises data combination means for adding stuffing data to the compressed audio data according to the transfer speed profile, and in that the recording means are arranged for recording transfer speed profile information on the record carrier for enabling playback at a transfer speed as indicated by the transfer speed profile information.
For this purpose a record carrier as described in the opening paragraph is characterized according to the invention in that the transfer speed information comprises transfer speed profile information, the transfer speed profile indicating the transfer speed at playback for an item of audio information, in which profile the average transfer speed is higher than an average transfer speed minimally required to transfer the compressed audio data of said item, and in that the record carrier comprises stuffing data in addition to the compressed audio data according to the transfer speed profile.
For this purpose a playback device as described in the opening paragraph is characterized according to the invention in that the device comprises data selection means for retrieving the transfer speed profile information from the record carrier and for removing stuffing data from the data retrieved, and in that the control unit is arranged for setting the transfer speed for an item of audio information according to the transfer speed profile.
The above means according to the invention enable transferring audio information via a record carrier as follows. On the record carrier the audio information is accessible for a user as one item or several separate items. An item of audio information is to be construed as a coherent amount of audio information of a certain playing time. An item may be a song or a set of songs, or a representation in stereo or a multi channel format, or the audio information may be subdivided in items of a certain playing time, e.g. for the convenience of the user in pieces of a few minutes like individual songs or parts of a the symphony, as usual on an audio CD. An item may be preceded and followed by silent the fragments or a pause of a few seconds, but it may also be a part of a larger and continuing piece of music. A transfer speed profile for an item of audio information indicates the actual transfer speed of the record carrier when reproducing the respective item.
Bakx Johannus L.
Bruekers Alphons A.M.L.
De Haan Wiebe
Van De Kerkhof Leon M.
Belk Michael E.
Dinh Tan
U.S. Philips Corporation
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