EP0413391A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Speech coding system and a method of encoding speech
Assignee: Philips Electronics UK Ltd
•
Filing: 1990-08-10
•
Granted: —
•
Expires: 2010-08-10
Abstract
Abstract A speech coding system of the code excited linear prediction (CELP) type comprises means (24,26) for filtering digitised speech samples to form perceptually weighted speech samples. Entries in a one-dimensional codebook (110) comprising frame length sequences are filtered in a perceptually weighted synthesis filter (28) to form a one-dimensional filtered codebook (38). The filtered codebook entries are compared with the perceptually weighted speech signals to obtain a codebook index which gives the minimum perceptually weighted error when the speech is resynthesised. Using a one-dimensional codebook (110) reduces the amount of computation which is required compared to using a two-dimensional codebook.
Inventors
- 👤 Timothy James Moulsley
- 👤 Patrick William Elliott
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 12:32
CPC Classifications
H; H03; H03M; H03M7/00; G; G10; G10L; G10L19/00; G10L19/04; G10L19/08; G10L19/12; G10L2019/0001; G10L2019/0002; G10L2019/0013; G10L2019/0014
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
59 words
A speech coding system comprising means for filtering digitised speech samples to form perceptually weighted speech samples, a one-dimensional codebook, means for filtering entries read-out from the codebook, and means for comparing the filtered codebook entries with the perceptually weighted speech signals to obtain a codebook index which gives the minimum perceptually weighted error when the speech is resynthesised.
Claim 2
Dependent Claim
59 words
A speech coding system comprising means for filtering digitised speech samples to form perceptually weighted speech samples, a one-dimensional codebook, means for filtering entries read-out from the codebook, and means for comparing the filtered codebook entries with the perceptually weighted speech signals to obtain a codebook index which gives the minimum perceptually weighted error when the speech is resynthesised.
Claim 3
Dependent Claim
22 words
A system as claimed in Claim 1, characterised in that the means for filtering the codebook entries comprises a perceptual weighting filter.
Claim 4
Dependent Claim
62 words
A system as claimed in Claim 1 or 2, characterised in that the means for filtering the digitised speech samples comprises a short term predictor and another perceptual weighting filter, and in that there is provided means for deriving the coefficients for the short term predictor and for the another perceptual weighting filter by linear predictive analysis of the digitised speech samples.
Claim 5
Dependent Claim
28 words
A system as claimed in Claim 3, when appended to Claim 2, characterised in that the transfer functions of the and the another perceptual weighting filters are different.
Claim 6
Dependent Claim
37 words
A system as claimed in Claim 4, characterised in that the means for comparing the filtered codebook entries with the perceptually weighted speech signals is adapted to search every pth entry, where p is greater than unity.
Claim 7
Independent Claim
82 words
A system as claimed in any one of Claims 1 to 5, characterised in that said comparing means is adapted to effect the comparison by calculating the sum of the cross products using the expression: where N is the number of digitised samples in a frame, n is the sample number, x is the signal being matched with the codebook, m is an integer having a low value g k is the unscaled filtered codebook sequence, and k is the codebook index.
Claim 8
Independent Claim
109 words
A system as claimed in any one of Claims 1 to 6, characterised in that there are provided means for forming a dynamic adaptive codebook from scaled entries selected from the filtered codebook, means for comparing entries from the dynamic adaptive codebook with perceptually weighted speech samples, means for determining an index which gives the smallest difference between the dynamic adaptive codebook entry and the perceptually weighted speech samples, means for subtracting the determined index from the perceptually weighted speech samples, and means for comparing the difference signal obtained from the subtraction with entries from the filtered codebook to obtain the filtered codebook index which gives the best match.
Claim 9
Dependent Claim
54 words
A system as claimed in Claim 7, characterised in that there are provided means for combining the filtered codebook entry which gives the best match with the corresponding dynamic adaptive codebook entry to form coded perceptually weighted speech samples, and filtering means for filtering the coded perceptually weighted speech samples to provide synthesised speech.
Claim 10
Dependent Claim
41 words
A system as claimed in Claim 8, characterised in that the dynamic adaptive codebook comprises a first-in, first out storage device of predetermined capacity and in that the input signals to the storage device comprise the coded perceptually weighted speech samples.
Claim 11
Dependent Claim
43 words
A system as claimed in Claim 8 or 9, characterised in that the filtering means for filtering the coded perceptually weighted samples comprise means for producing an inverse transfer function compared to the transfer function used to produce the perceptually weighted speech samples.
Claim 12
Independent Claim
64 words
A method of encoding speech in which digitised speech samples are filtered to produce perceptually weighted speech samples, entries are selected from a 1-dimensional code book and are filtered to form a filtered codebook, the perceptually weighted speech samples are compared with entries from the filtered codebook to obtain a codebook index which gives the minimum perceptually weighted error when the speech is resynthesised.
Claim 13
Independent Claim
64 words
A method of encoding speech in which digitised speech samples are filtered to produce perceptually weighted speech samples, entries are selected from a 1-dimensional code book and are filtered to form a filtered codebook, the perceptually weighted speech samples are compared with entries from the filtered codebook to obtain a codebook index which gives the minimum perceptually weighted error when the speech is resynthesised.
Claim 14
Dependent Claim
20 words
A method as claimed in Claim 11, characterised in that the codebook entries are filtered using a perceptual weighting filter.
Claim 15
Dependent Claim
56 words
A method as claimed in Claim 11 or 12, characterised in that the digitised speech samples are filtered using a short term predictor and another perceptual weighting filter, and in that the coefficients for the short term predictor and for the another perceptual weighting filter are derived by linear predictive analysis of the digitised speech samples.
Claim 16
Dependent Claim
22 words
A method as claimed in Claim 13, characterised in that the coefficients of the and the another perceptual weighting filter are different.
Claim 17
Dependent Claim
23 words
A method as claimed in Claim 14, characterised in that every pth filtered codebook entry is searched, where p is greater than unity.
Claim 18
Independent Claim
88 words
A method as claimed in any one of Claims 11 to 15, characterised in that the comparison of the perceptually weighted speech samples with entries from the filtered codebook is by calculating the sum of the cross products using the expression where N is the number of digitised samples in a frame, n is the sample number, x is the signal being matched with the codebook, g k is the unscaled filtered codebook sequence, k is the codebook index, and m is an integer having a low value.
Claim 19
Independent Claim
94 words
A method as claimed in any one of Claims 11 to 16, characterised by forming dynamic adaptive codebook from scaled entries selected from the filtered codebook, comparing entries from the dynamic adaptive codebook with perceptually weighted speech samples, determining an index which gives the smallest difference between the dynamic adaptive codebook entry and the perceptually weighted speech samples, subtracting the determined entry from the perceptually weighted speech samples and comparing the difference signal obtained by the subtraction with entries from the filtered codebook to obtain the filtered codebook index which gives the best match.
Claim 20
Dependent Claim
45 words
A method as claimed in Claim 17, characterised by combining the filtered codebook entry which gives the best match with the corresponding dynamic adaptive codebook entry to form coded perceptually weighted speech samples and filtering the coded perceptually weighted speech samples to provide synthesised speech.
Claim 21
Dependent Claim
34 words
A method as claimed in Claim 18, characterised in that the coded perceptually weighted samples are filtered using a transfer function which is the inverse of that to produce the perceptually weighted speech samples.
Claim 22
Independent Claim
98 words
A method of deriving speech comprising forming a filtered codebook by filtering a one dimensional codebook using a filter whose coefficients are specified in an input signal, selecting a predetermined sequence specified by a codebook index in the input signal, adjusting the amplitude of the selected predetermined sequence in response to a gain signal contained in the input signal, restoring the pitch of the selected predetermined sequence in response to pitch predictor index and gain signals contained in the input signal, and applying the pitch restored sequence to deweighting and inverse synthesis filters to produce a speech signal.
Claim 23
Independent Claim
98 words
A method of deriving speech comprising forming a filtered codebook by filtering a one dimensional codebook using a filter whose coefficients are specified in an input signal, selecting a predetermined sequence specified by a codebook index in the input signal, adjusting the amplitude of the selected predetermined sequence in response to a gain signal contained in the input signal, restoring the pitch of the selected predetermined sequence in response to pitch predictor index and gain signals contained in the input signal, and applying the pitch restored sequence to deweighting and inverse synthesis filters to produce a speech signal.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.