Jim C Chevalley, 77880 32Nd Ave, San Francisco, CA 94121

5222069, Jun 22, 1993

Sep 20, 1990

7/586490

Jim C. Chevalley - San Francisco CA

Ampex Systems Corporation - Redwood City CA

G11B 2018

371 403

With a digital audio or video recorder/playback decoder, an erasure flag signals (1) that an error(s) was not detected in a video signal or that an error(s) was detected and was corrected or (2) that an error(s) was detected and was not corrected. Decoders either (1) may not detect certain errors, called "unflagged errors," or (2) may detect certain errors but not correct those errors, called "flagged errors. " Here, video signal data, which may have flagged or unflagged errors, is concealed. The structure detects an unflagged error in the digital data and modifies the concealment flag of that digital data. The structure also detects a first-good sample of digital data; sets the erasure flag of the first-good sample to indicate that it is to be treated as having a detected error; and extends the first-good sample to an ECC system and to a miscorrection detector. The first-good sample and a corresponding sample at the output of the ECC system are compared and (1), if the compared samples are the same, the structure modifies the concealment flag of the first-good sample to a "good" value or (2), if the compared samples are not the same, modifies the concealment flag of the first-good sample or the entire data block of which the good-sample is an element to a "bad" value dependent on whether the then existing concealment flag of the corresponding sample output is itself bad or good, respectively.