Digital signal reproducing apparatus

Claim 2

In a device for recording and/or reproducing magnetic recordings: a video signal circuit comprising: means for recording data on a recording media and for obtaining a reproduced signal from said recording media; and means responsive to a change in the value of instant input data for correcting the value of a prior input data.

Claim 3

In a device using a partial response method for reproducing predetermined data recorded on a magnetic recording medium, the combination of: means for reproducing the recorded data; Viterbi decoding circuit means for decoding the reproduced data; detecting means for detecting the level of decoded reproduced data output from said Viterbi decoding circuit means; means for comparing the detected level of the decoded reproduced data with a predetermined level; means for determining if the compared detected level falls within a predetermined range; and means for correcting the level of the decoded data which falls within said predetermined range.

Claim 4

In a device using a partial response method for reproducing predetermined data recorded on a magnetic recording medium, the combination of: means for reproducing the recorded data; Viterbi decoding circuit means for decoding the reproduced data; detecting means for detecting the level of decoded reproduced data output from said Viterbi decoding circuit means; means for comparing the detected level of the decoded reproduced data with a predetermined level; means for determining if the compared detected level falls within a predetermined range; and means for correcting the level of the decoded data which falls within said predetermined range.

Claim 5

In a system for reproducing recorded data, the combination of: means for converting an input signal from analog form to the form of digital data; a moving magnetic recording medium; means for magnetically recording said data on said record medium; means for reading data recorded on said moving medium and producing an analog playback signal indicative thereof; means for converting said analog playback signal into a digital playback signal; signal dividing means for dividing said digital playback signal into first and second signal portions; first and second Viterbi decoding circuits which respectively receive said first and second signal portions; signal re-combining means for receiving outputs of said first and second Viterbi decoding circuits and forming a reconstituted digital signal therefrom; means for converting said reconstituted digital signal into an analog output signal; and modifying means associated with said first and second Viterbi decoding circuits for modifying either the outputs of said first and second Viterbi circuits or the signal portions respectively received by said Viterbi decoding circuits so as to reduce the bit error in the outputs of said first and second Viterbi circuits.

Claim 6

In a system for reproducing recorded data, the combination of: means for converting an input signal from analog form to the form of digital data; a moving magnetic recording medium; means for magnetically recording said data on said record medium; means for reading data recorded on said moving medium and producing an analog playback signal indicative thereof; means for converting said analog playback signal into a digital playback signal; signal dividing means for dividing said digital playback signal into first and second signal portions; first and second Viterbi decoding circuits which respectively receive said first and second signal portions; signal re-combining means for receiving outputs of said first and second Viterbi decoding circuits and forming a reconstituted digital signal therefrom; means for converting said reconstituted digital signal into an analog output signal; and modifying means associated with said first and second Viterbi decoding circuits for modifying either the outputs of said first and second Viterbi circuits or the signal portions respectively received by said Viterbi decoding circuits so as to reduce the bit error in the outputs of said first and second Viterbi circuits.

Claim 7

A system according to claim 3; wherein said modifying means includes: comparator means operatively connected with said first and second Viterbi decoding circuits in a manner to receive data which indicates differences between values of sequentially received signal portions, said comparator means being operative to compare said difference indicating data with a reference value, and a variable gain amplifier connected with said comparator means and arranged between said means for reading the data recorded on said moving recording medium and producing an analog playback signal indicative thereof and said means for converting the analog playback signal into a digital playback signal.

Claim 8

A system according to claim 3; wherein said modifying means includes first and second level detection means for detecting the levels of said first and second signal portions, respectively, and for controlling the operations of said first and second Viterbi decoding circuits, respectively.

Claim 9

A system according to claim 3; wherein each of said first and second Viterbi decoding circuits comprises: an input terminal for receiving the respective one of said signal portions; first and second adders having respective inputs connected with said input terminal and further having respective outputs; multiplier means; first and second comparators having respective outputs connected to said multiplier means; latch means including a memory, a latch input connected to said output of the second adder and a latch output connected to inputs of said second comparator and said first adder, said output of the first adder being connected to an input of said first comparator, and said output of the first comparator being connected to another input of said second adder; a control circuit connected to an output of said multiplier; and a data memory circuit having a first input connected with said output of the second comparator and a second input connected with an output of said control circuit.

Claim 10

A system according to claim 6; wherein said modifying means comprises: level detection means for detecting the level of said respective signal portion, said level detection means having an output which is connected to another input of said first comparator, said first comparator being responsive to said level detection means in a manner to change a decision level therein.

Claim 11

A system according to claim 6; wherein said modifying means comprises: a third comparator operatively connected with said latch output; and variable gain amplifier means controllable by an output from said third comparator and arranged between said means for reading the recorded data and producing an analog playback signal indicative thereof and said means for converting the analog playback signal into a digital playback signal.