Encoding rate-based, programmable, linear velocity, compressed audio compact disc player
AssigneeTexas Instruments Incorporated
InventorsStephen J. Fedigan, Thomas N. Millikan
Life of this patent
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Abstract
An audio player permits compressed or uncompressed audio CDs to be played. The preferred player includes a spindle motor control that causes the CD to be spun at a constant linear velocity that is commensurate with the encoding rate of the file being played. In this manner, the data can be continuously pulled of the CD at just the right rate so that, after being decoded and decompressed, the data can be played. The player also dynamically adjusts its constant linear velocity to the encoding rate of the file being played to permit files on the same disc having different encoding rates to be played.
Claims17
A compressed audio player, comprising:
- an optical pickup;
- processing logic coupled to said optical pickup and receiving a compressed bit stream from said optical pickup;
- a programmable motor control coupled to said processing logic;
- and
- a motor coupled to said programmable motor control;
- wherein said processing logic determines the encoding rate of compressed audio on the disc and programs the programmable motor control to operate the motor so as to spin a disc at a constant linear velocity that is a function of the encoding rate of the compressed audio;
- and
- wherein said programmable motor control includes a programmable frequency divider that divides down a reference clock by a division factor determined by said processing logic.
A method of playing compressed audio files from a CD being spun at a constant linear velocity by a motor, comprising the steps of:
- (a) retrieving compressed audio data from the CD;
- (b) determining the encoding rate of said compressed audio data;
- and
- (c) adjusting the constant linear velocity of the motor according to the encoding rate of said compressed audio data, said adjusting step including
- (1) recovering a clock signal from compressed audio data from the CD,
- (2) dividing a reference clock signal by a division factor,
- (3) comparing the phase of the divided reference clock signal with the phase of the recovered clock signal to produce an error signal,
- (4) controlling the constant linear velocity of the motor according to said error signal, and
- (5) controlling the division factor to minimize said error signal.
A programmable motor control, comprising:
- a first frequency divider which receives a recovered clock from a compressed audio bit stream;
- a second frequency divider which receives a reference clock;
- a phase comparator which compares the divided down frequencies from the first and second dividers;
- wherein said phase comparator produces an average output voltage relative to the phase difference of the divided down frequencies from the first and second frequency dividers;
- and
- wherein the second frequency divider is programmed to divide down the reference clock by an amount that is a function of the encoding rate of the compressed audio bit stream.
Dependencies are inferred from the claim text.