Sony Corporation

Peter C Boreland

James Hedley Wilkinson

John G Ive

Concealing errors in a digital television signal, which has a plurality of component sample values corresponding respectively to sample positions along a horizontal scan line of a television picture made up of a plurality of scan lines, in respect of each sample value which is in error, by calculating a first concealment accuracy by determining the difference between two immediately adjacent sample values both in the scan line immediately preceding or following the scan line which the error sample is in, and one of which sample values is immediately adjacent to the error sample, calculating a second concealment accuracy by determining the difference between two immediately adjacent sample values both in the vertical line immediately preceding or following the vertical line which the error sample is in, and one of which sample values is immediately adjacent to the error sample, selecting from the available concealment accuracies a preferred direction of the television picture for concealing the error sample, calculating a corrected value of the error sample using available sample values disposed along the preferred direction, and substituting the corrected sample value for the error sample so as to conceal the error.

Error concealment in digital television signals

A method of recording a digital audio signal in association with a digital video signal which is to be recorded in oblique tracks on a magnetic tape using a rotary head the rotational frequency of which is locked to the digital video signal, comprises the steps of assembling incoming audio data words which correspond to successive samples of an audio signal into groups nominally of N audio data words where N is the number of audio samples corresponding to the digital video signal to be recorded in one oblique track, allowing the number of audio data words in each group to vary preferably over the range N-1 to N+1 to maintain synchronism of the audio signal with the rotational frequency of the rotary head, coding the audio data words into error-correcting blocks for recording by the rotary head, and associating with each error-correcting block a status code for use on reproduction and which indicates whether the number of audio data words in the corresponding group is N-1, or N+1.

Recording and reproducing digital audio signals formed into groups of

Apparatus for concealing errors in a digital television signal comprises delay elements for deriving a current sample value and a first group of the sample values spatially closest to the current sample value in the same frame of the television signal and delay elements for deriving from the preceding frame of the television signal a delayed sample value corresponding in position to the current sample value and a second group of sample values respectively corresponding in position to the sample values. The current sample value and the delayed sample value are checked for error, and subtractors check pairs of sample values corresponding in position in the current and preceding frames of the television signal for error, derive a measure of the difference in the levels of the sample values in each pair, and combine the results of these checks to provide an output signal which is a measure of the number of the errors and of the sum of the differences. A threshold device checks the output signal against a predetermined threshold level corresponding to an acceptably small number of errors and a relative low degree of movement in the part of a television picture corresponding to the groups of sample values, and a selector is operative, if the sample value is in error, the delayed sample value in not in error, and the output signal is below the predetermined level, to replace the current sample value by the delayed sample value for supply to an output, and, in all other cases, to supply the current sample value to the output.

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Waterbury, CT, United States of America

Peter C Boreland