Apparatus for playback of magnetically recorded data having a variable input rate

Claim 1

Apparatus for playback of data received at a variable input rate and recorded on a longitudinal recording medium, utilizing a playback transducer mounted on a rotating scanner drum, said input data rate being maintained constant during a particular recording operation, said data being recorded in the form of fixed length data blocks having variable spacing between said blocks, corresponding to said variable rate, a data block marker being recorded at the beginning of each block, and wherein said input data rate is encoded and recorded on said medium, comprising: playback synchronizing means (54) for providing an internal data transfer clock having a nominal rate, and deriving therefrom synchronously a signal for controlling a rate of rotation of said scanner drum during playback; an output clock generator (64) for providing an adjustable, stable data output clock; output control means (60) for receiving and decoding said played back input data rate, and providing responsively a first control signal applied to said data output clock generator means to adjust a rate of said data output clock to correspond to said input data rate; correlator means (20) for receiving said playback data and detecting said data block marker, and providing responsively a second, beginning of data block control signal; memory means (36) for receiving and storing said playback data at said internal data transfer clock rate, said stored data being read therefrom sequentially at said data output clock rate, said memory providing a third, memory status control signal corresponding to a predetermined level of fullness thereof, said third control signal being provided to coincide with said second control signal pertaining to a next sequential data block when an average amount of data being written into said memory is equal to an average amount of data being read from the memory; and memory write control means (34) receiving said second and third control signals, enabling input of a data block into said memory means in response to said second control signal, and detecting a difference in time between the occurrences of said second and third control signals, and applying responsively an error signal to said playback synchronizing signal generator means to adjust said internal data transfer clock rate to compensate for said time difference.

Claim 10

A method of playback of data received at a variable input rate and recorded on a longitudinal recording medium, said input data rate being maintained constant during a particular recording operation, said data being recorded in the form of fixed length data blocks having variable spacing between said blocks, corresponding to said variable rate, a data block marker being recorded at the beginning of each block, and wherein said input data rate is encoded and recorded on said medium, the method comprising: providing an internal data transfer clock having a nominal rate; providing an adjustable, stable data output clock; receiving and decoding the played back input data rate; adjusting said data output clock to correspond to said input data rate' receiving the played back data and detecting said data block marker, and providing responsively a control signal denoting the beginning of a data block; receiving and storing in a memory the played back data at the internal data transfer clock rate, the stored data being read from memory sequentially at said the output clock rate, providing a memory status control signal corresponding to a predetermined level of fullness of the memory; enabling input of a data block into the memory in response to said memory status control signal; detecting a difference in time between the occurrences of said control signals; and applying adjustment of the internal data transfer clock rate to compensate for said time difference.

Claim 11

A method of playback of data received at a variable input rate and recorded on a longitudinal recording medium, said input data rate being maintained constant during a particular recording operation, said data being recorded in the form of fixed length data blocks having variable spacing between said blocks, corresponding to said variable rate, a data block marker being recorded at the beginning of each block, and wherein said input data rate is encoded and recorded on said medium, the method comprising: providing an internal data transfer clock having a nominal rate; providing an adjustable, stable data output clock; receiving and decoding the played back input data rate; adjusting said data output clock to correspond to said input data rate' receiving the played back data and detecting said data block marker, and providing responsively a control signal denoting the beginning of a data block; receiving and storing in a memory the played back data at the internal data transfer clock rate, the stored data being read from memory sequentially at said the output clock rate, providing a memory status control signal corresponding to a predetermined level of fullness of the memory; enabling input of a data block into the memory in response to said memory status control signal; detecting a difference in time between the occurrences of said control signals; and applying adjustment of the internal data transfer clock rate to compensate for said time difference.