Error protection system for a sub-band coder suitable for use in an audio signal processor

A method of decoding digital audio information comprising sub-band audio signals;

• a scaling factor for sub-band coded audio signal components;
• and data blocks comprising (a) a header including control information, (b) a first error processing code relative to said header, (c) an audio data field including said scaling factors, (d) an ancillary information field including ancillary information relating to said audio signals and (e) a second error processing code for protecting said scaling factors, said code being inserted near the end of said data blocks in a region that incorporates items of said ancillary information, wherein said method of decoding comprises thesteps of:
• detecting a scaling factor level change,
• comparing said change with a statistically expected level change, said detected level change being considered erroneous if a deviation from said expected change is detected, and
• compensating for an erroneous scale factor change.

Apparatus for decoding digital audio information comprising sub-band audio signals;

• a scaling factor for sub-band coded audio signal components;
• and data blocks comprising (a) a header including control information, (b) a first error processing code relative to said header, (c) an audio data field including said scaling factors, (d) an ancillary information field including ancillary information relating to said audio signals and (e) a second error processing code for the protecting said scaling factors, said second code being inserted near the end of said data blocks in a region that incorporates items of said ancillary information, said apparatus comprising:
• a source of said data blocks;
• means coupled to said source for extracting said second code and said scaling factors from said data blocks;
• means responsive to said scaling factors and to said second code for compensating for erroneous scaling factors using said second code;
• and
• means responsive to said scaling factors for decoding said coded audio signals.

A medium storing method for producing a coded digital audio signal, said method comprising the steps of:

• sub-band coding said audio signals,
• generating a scaling factor for sub-band coded audio signal components;
• and
• generating data blocks comprising:
• (a) a header including control information,
• (b) a first error processing code relative to said header,
• (c) an audio data field including said scaling factors,
• (d) an ancillary information field including ancillary information relating to said audio signals and
• (e) a second error processing code for protecting said scaling factors, said second code being inserted near the end of said data blocks in a region that incorporates items of said ancillary information.

A method of communicating a digital audio signal, comprising the steps of:

• (a) sub-band coding said audio signal, wherein at least one scale factor is associated with a sub-band;
• (b) transmitting said sub-band coded audio signal in successive data frames, wherein a data frame includes:
• (a1) a header including control information;
• (a2) an audio data code including:
• a bit allocation table;
• scale factor selection information;
• a scale factor;
• and
• sampling values associated with said sub-bands;
• (a3) error detection data including a first error protection code, wherein said first protection code is a Cyclic Redundancy Check (CRC) code for detection of transmission errors in said header, said scale factor selection information and said bit allocation table;
• and
• (a4) an ancillary information field containing information concerning said audio data signal and including a second CRC protection code for protecting the MSB's of said scale factor, wherein said second protection code is inserted at the end of said data frame in a region of said data frame that incorporates items of said ancillary information.

A method of receiving a sub-band coded digital audio signal organized in successive data frames, wherein at least one scale factor is associated with a sub-band, said method comprising the steps of:

• (a) decoding information in a data frame of said sub-band coded audio signal, including:
• (a1) a header including control information;
• (a2) an audio data code including:
• a bit allocation table;
• scale factor selection information;
• a scale factor;
• and
• sampling values associated with said sub-bands;
• (a3) error detection data including a Cyclic Redundancy Check (CRC) first error protection code for detecting transmission errors in said header, said scale factor selection information and said bit allocation table;
• and
• (a4) an ancillary information field containing information concerning said audio data signal and including a second CRC protection code for protecting the MSB's of said scale factor, wherein said second protection code is inserted at the end of said data frame in a region of said data frame that incorporates items of said ancillary information;
• and
• (b) reproducing audio information using an item of decoded data frame information produced in step (a).