Method and apparatus for concealing errors in a digital television

• US 5,243,428 A
• Filed: 10/08/1991
• Issued: 09/07/1993
• Est. Priority Date: 01/29/1991
• Status: Expired due to Term

• Current Assignee: IPG Electronics 503 Limited (Coller IP Capital Limited)
• Original Assignee: North American Philips Corp. (Koninklijke Philips N.V.)
• Inventors: Challapali, Kiran S., Azadegan, Faramarz
• Primary Examiner(s): Powell, Mark R.
• Application Number:
  US07/774,006
• Time in Patent Office: 700 Days
• Field of Search: 371/31, 371/41, 358/167, 358/36, 358/37, 358/133, 358/166, 358/160, 358/105
• US Class Current: 348/607
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04N 21/426 Internal components of the client ; Characteristics thereof H04N5/44 takes precedence
• CPC Class Codes: H04N 5/211 Ghost signal cancellation H04N23/81 takes precedence
• CPC Class Codes: H04N 5/44 Receiver circuitry for the reception of television signals according to analogue transmission standards H04N5/14 takes precedence
• CPC Class Codes: H04N 7/063 Simultaneous transmission of separate parts of one picture
• CPC Class Codes: H04N 7/08 Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band , e.g. by time division H04N7/007 takes precedence

Abstract

A method and apparatus for concealing errors occurring during the transmission and or reception of digital television signals. Blocks of video information are received and if any of the blocks contain errors including missing coefficients and/or motion vectors which are not correctable by the error correction circuitry, they are concealed by deriving replacement coefficients and/or motion vectors from at least one of the other received blocks of video.

Claims

1. A method for concealing errors present in a sequence of blocks provided by a digital video compression system wherein a digital video signal is processed as a sequence of frames, said frames comprising intra-coded frames and predictive coded frames, each of said intra-coded frames comprising blocks which each comprise coefficients derived from said video signal, and each of said predictive coded frames comprising blocks which each comprise motion vectors derived from said video signal, and wherein an error signal is provided for a first block having an error, said method comprising the steps of:

a) storing said sequence of blocks including said first block so as to provide a sequence of output blocks delayed in time;

b) storing said error signal so as to provide an output error signal synchronized in time with said first block;

c) deriving a corrected block comprising information needed to conceal the error in said first block, whereby if said error consists of a loss of a coefficient, said information is replacement coefficient derived from coefficients of at least one of said stored plurality of blocks, and if said error consists of a loss of a motion vector, said information is a replacement motion vector derived from at least one motion vector of at least one of said stored plurality of blocks; and

d) substituting said corrected block for said first block in said sequence of output blocks in the presence of said output error signal.

2. The method described in claim 1 wherein said blocks of video information are coded from a source image having a first bandwidth to permit conveyance over a channel having a bandwidth which is more narrow than said first bandwidth.

3. An apparatus for concealing errors present in a sequence of blocks provided by a digital video compression system wherein a digital video signal is processed as a sequence of frames, said frames comprising intra-coded frames and predictive coded frames, each of said intra-coded frames comprising blocks which each comprise coefficients derived from said video signal, and each of said predictive coded frames comprising blocks which each comprise motion vectors derived from said video signal, and wherein an error signal is provided for a first block having an error, said apparatus comprising in combination:

a) first storage means for storing said sequence of blocks including said first block so as to provide a sequence of output blocks delayed in time;

b) second storage means for storing said error signal so as to provide an output error signal synchronized in time with said first block;

c) concealing means for receiving said sequence of blocks and said error signal and for deriving, upon detection of said output error signal, a corrected block comprising information needed to conceal the error in said first block, whereby if said error consists of a loss of a coefficient, said information is replacement coefficient derived from coefficients of at least one of said stored plurality of blocks, and if said error consists of a loss of a motion vector, said information is a replacement motion vector derived from at least one motion vector of at least one of said stored plurality of blocks; and

d) switching means coupled to said first and second storage means and said concealing means, for receiving as a first input said sequence of output blocks, as a second input said output error signal, and as a third input said corrected block, and for substituting, upon detection of said output error signal, said corrected block for said first block in said sequence of output blocks.

4. A television receiver comprising an apparatus for concealing errors present in a sequence of blocks provided by a television signal comprising a sequence of frames, said frames comprising intra-coded frames and predictive coded frames, each of said intra-coded frames comprising blocks which each comprise coefficients derived from said video signal, and each of said predictive coded frames comprising blocks which each comprise motion vectors derived from said video signal, and wherein an error signal is provided for a first block having an error, said apparatus comprising in combination:

a) first storage means for storing said sequence of blocks including said first block so as to provide a sequence of output blocks delayed in time;

b) second storage means for storing said error signal so as to provide an output error signal synchronized in time with said first block;

c) concealing means for receiving said sequence of blocks and said error signal and for deriving, upon detection of said output error signal, a corrected block comprising information needed to conceal the error in said first block, whereby if said error consists of a loss of a coefficient, said information is replacement coefficient derived from coefficients of at least one of said stored plurality of blocks, and if said error consists of a loss of a motion vector, said information is a replacement motion vector derived from at least one motion vector of at least one of said stored plurality of blocks; and

d) switching means coupled to said first and second storage means and said concealing means, for receiving as a first input said sequence of output blocks, as a second input said output error signal, and as a third input said corrected block, and for substituting, upon detection of said output error signal, said corrected block for said first block in said sequence of output blocks.