Recording digital signals

Claim 3

A method according to claim 1 wherein the sampling is a `n` times the subcarrier frequency and wherein the information for replacing the word in error is derived from words of the same line that are `n` displaced before and after the word in error.

Claim 4

A method according to claim 1, and wherein sampling occurs at two times subcarrier frequency.

Claim 5

A method according to claim 1, wherein the recording step further comprises processing the words by delaying words in one channel with respect to words representing adjacent samples of the same phase in another channel.

Claim 6

A method according to claim 4, wherein the recording step further comprises combining the channels and recording them on a single track on a recording medium.

Claim 7

A method according to claim 1, wherein each channel is recorded as a separate track on a recording medium.

Claim 8

A method according to claim 6, wherein there are two tracks and wherein sampling occurs at `n` times subcarrier frequency and `n` successive words are recorded on a first track before a further `n` successive words are recorded on the other track.

Claim 9

A method according to claim 6, wherein there are two tracks and wherein sampling occurs at three times subcarrier frequency, succeeding words being recorded on alternate tracks.

Claim 10

The method as defined in claim 1, wherein the analog signal represents a line of a video raster.

Claim 11

A method of correcting errors in digital video signals recorded by the method according to claim 9, and comprising detecting a word in error and replacing that word using information derived from at least one digital word from the same video line and of the same phase of subcarrier as the word in error.

Claim 12

A method according to claim 10, wherein when a word in error is detected a corresponding word from a previous line is retained in a memory.

Claim 13

A method according to claim 11, wherein the corresponding word from two lines previously is retained.

Claim 14

The method as defined in claim 1, and further including the steps of (f) detecting the individual words of each channel recorded on said recording medium, respectively; (g) separating the words of each channel, respectively; (h) examining the error detection signals of the words of each channel to detect an error therein; (i) storing in data storage means for each channel the correct words that do not contain an error; (j) storing in error storage means for each channel the words that contain errors: and (k) generating, in response to the correct words stored in said data storage means, a replacement word for a given word in error.

Claim 15

A method according to claim 13, wherein said at least one digital word is from the same line of video.

Claim 16

A method according to claim 13, wherein said at least one digital word is from a previous line of video.

Claim 17

Apparatus for recording an alternating current analog signal in a manner to alleviate drop-outs, said signal having a given subcarrier frequency (f sc ), comprising (a) means including an analog to digital converter (10) for sampling the analog signal at a sampling frequency which is a multiple of the subcarrier frequency (f sc ), and for producing a plurality of digital words constituted by a plurality of bits; (b) means (11, 12a, 12b) for introducing into said digital words an error detection signal (P); (c) means (16a, 16b; and 16c, 16d) for storing groups of said digital words in at least two separate channels, respectively, a first group of words of one channel including first and second subgroups of words of different phase relative to each other, and a second group of words of the other channel including third and fourth subgroups of words of different phase relative to each other; (d) at least two parallel to series converter means (17a, 17b) for serializing the subgroups of words of each channel, respectively; and (e) at least two recording devices (18a, 18b) for recording on a recording medium the serialized channel signals from said parallel to series converter means, respectively.

Claim 18

Apparatus for recording an alternating current analog signal in a manner to alleviate drop-outs, said signal having a given subcarrier frequency (f sc ), comprising (a) means including an analog to digital converter (10) for sampling the analog signal at a sampling frequency which is a multiple of the subcarrier frequency (f sc ), and for producing a plurality of digital words constituted by a plurality of bits; (b) means (11, 12a, 12b) for introducing into said digital words an error detection signal (P); (c) means (16a, 16b; and 16c, 16d) for storing groups of said digital words in at least two separate channels, respectively, a first group of words of one channel including first and second subgroups of words of different phase relative to each other, and a second group of words of the other channel including third and fourth subgroups of words of different phase relative to each other; (d) at least two parallel to series converter means (17a, 17b) for serializing the subgroups of words of each channel, respectively; and (e) at least two recording devices (18a, 18b) for recording on a recording medium the serialized channel signals from said parallel to series converter means, respectively.

Claim 19

Apparatus as defined in claim 16, and further including (f) means (18a, 18b, 25) for detecting the individual words of each channel recorded on said recording medium, respectively; (g) means (26) for separating the words of each channel, respectively; (h) error detector means (30) for each channel for examining the error detection signals of the words to detect an error therein; (i) data storage means (32, 34) for each channel for storing those words that do not contain an error; (j) error storage means (36, 38) for each channel for storing the words that contain errors; and (k) error concealing means (45) responsive to the correct words stored in said data storage means for generating a replacement word for a given word in error.

Claim 20

Apparatus as defined in claim 17, and further including data selector means (39, 41) for supplying to said error concealing means in series the words contained in said storage means, said error concealing means including an averaging means (45e), and word latch means (45a-45d) for feeding words successively to said averaging means at a frequency which is the same as the sampling frequency of the analog signals.