Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
226 words
A method of improving the detection and masking of bad frames in a coded speech signal resulting from channel transmission errors, said coded speech signal having a first group of bits comprising the most significant bits of said coded speech signal, error detection bits and error correction bits, a second group of bits comprising the second most significant bits and error correction bits and a third group of bits comprising the least significant bits, said method comprising the steps of: de-interleaving said coded signal to obtain a first series of bits comprising said first and second group of bits and a second series of bits comprising said third group of bits; convolutionally decoding said first series of bits for recovering said first and second group of bits; performing a Cyclic Redundancy Code (CRC) check on recovered bits of said first group; if said CRC check is successful, utilizing said third group of bits and said recovered bits of said first group for speech decoding and performing a maximum likelihood check on said second group of bits; if said maximum likelihood check is successful, utilizing said recovered bits of said second group for speech decoding; and if said maximum likelihood check is unsuccessful, replicating the pitch lag value and sub-frame gain for each sub-frame of said bad frame, from the last sub-frame of the previously accepted frame.
Claim 2
Independent Claim
226 words
A method of improving the detection and masking of bad frames in a coded speech signal resulting from channel transmission errors, said coded speech signal having a first group of bits comprising the most significant bits of said coded speech signal, error detection bits and error correction bits, a second group of bits comprising the second most significant bits and error correction bits and a third group of bits comprising the least significant bits, said method comprising the steps of: de-interleaving said coded signal to obtain a first series of bits comprising said first and second group of bits and a second series of bits comprising said third group of bits; convolutionally decoding said first series of bits for recovering said first and second group of bits; performing a Cyclic Redundancy Code (CRC) check on recovered bits of said first group; if said CRC check is successful, utilizing said third group of bits and said recovered bits of said first group for speech decoding and performing a maximum likelihood check on said second group of bits; if said maximum likelihood check is successful, utilizing said recovered bits of said second group for speech decoding; and if said maximum likelihood check is unsuccessful, replicating the pitch lag value and sub-frame gain for each sub-frame of said bad frame, from the last sub-frame of the previously accepted frame.
Claim 3
Dependent Claim
66 words
A method as defined in claim 1, further comprising the steps of: if said CRC check is not successful, replicating the frame energy and LPC parameters for said first and third group of bits; replicating the frame energy, LPC parameters, lag value and sub-frame gain for said second group of bits; and utilizing the replicated bits of said first, second and third groups for speech decoding.
Claim 4
Dependent Claim
18 words
A method as defined in claim 1, wherein said convolutional decoding comprises a Viterbi maximum likelihood convolution decoding.
Claim 5
Dependent Claim
33 words
A method as defined in claim 3, wherein said maximum likelihood check is successful if a metric assigned to the final surviving path by said Viterbi decoding is less than a predetermined threshold.
Claim 6
Dependent Claim
16 words
A method as defined in claim 4, wherein said metric is defined a the Hamming distance.