Data processing: speech signal processing – linguistics – language – Speech signal processing – Synthesis
Patent
1996-11-07
2000-05-23
Hudspeth, David R.
Data processing: speech signal processing, linguistics, language
Speech signal processing
Synthesis
704267, 704268, G10L 1306
Patent
active
060675195
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to speech synthesis, and is particularly concerned with speech synthesis in which stored segments of digitised waveforms are retrieved and combined.
SUMMARY OF THE INVENTION
According to the present invention there is provided a method of speech synthesis comprising the steps of: desired speech waveform and first pitch data defining excitation instants of the waveform; desired speech waveform and second pitch data defining excitation instants of the second waveform; extension sequence, the extension sequence being pitch adjusted to be synchronous with the excitation instants of the respective other sequence; sequence(s) and samples of the extension sequence(s).
In another aspect of the invention provides an apparatus for speech synthesis comprising the steps of: speech waveform and pitch data defining excitation instants of those waveforms; digital samples corresponding to desired portions of speech waveform and the corresponding pitch data defining excitation instants of the waveform; in operation (a) to synthesise from at least the first of a pair of retrieved sequences an extension sequence to extend that sequence into an overlap region with the other sequence of the pair, the extension sequence being pitch adjusted to be synchronous with the excitation instants of that other sequence and (b) to form for the overlap region weighted sum of samples of the original sequence(s) and samples of the extension sequence(s).
Other aspects of the invention are defined in the sub-claims.
BRIEF DESCRIPTION OF THE DRAWING
Some embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a block diagram of one form of speech synthesiser in accordance with the invention;
FIG. 2 is a flowchart illustrating the operation of the joining unit 5 of the apparatus of FIG. 1; and
FIG. 3 to 9 are waveform diagrams illustrating the operation of the joining unit 5.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
In the speech synthesiser of FIG. 1, a store 1 contains speech waveform sections generated from a digitised passage of speech, originally recorded by a human speaker reading a passage (of perhaps 200 sentences) selected to contain all possible (or at least, a wide selection of) different sounds. Thus each entry in the waveform store 1 comprises digital samples of a portion of speech corresponding to one or more phonemes, with marker information indicating the boundaries between the phonemes. Accompanying each section is stored data defining "pitchmarks" indicative of points of glottal closure in the signal, generated in conventional manner during the original recording.
An input signal representing speech to be synthesised, in the form of a phonetic representation, is supplied to an input 2. This input may if wished be generated from a text input by conventional means (not shown). This input is processed in known manner by a selection unit 3 which determines, for each unit of the input, the addresses in the store 1 of a stored waveform section corresponding to the sound represented by the unit. The unit may, as mentioned above, be a phoneme, diphone, triphone or other sub-word unit, and in general the length of a unit may vary according to the availability in the waveform store of a corresponding waveform section. Where possible, it is preferred to select a unit which overlaps a preceding unit by one phoneme. Techniques for achieving this are described in our CO-pending International patent application no. PCT/GB/9401688 and U.S. patent application Ser. No. 166,988 of 16 Dec. 1993.
The units, once read out, are each individually subjected to an amplitude normalisation process in an amplitude adjustment unit 4 whose operation is described in our co-pending European patent application no. 95301478.4.
The units are then to be joined together, at 5. A flowchart for the operation of this device is shown in FIG. 2. In this description a unit and the unit which fol
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Hirokawa et al, "High Quality Speech Synthesis System Based on Waveform Concatenation of Phoneme Segment", IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, vol. 76A, No. 11, Nov. 1993, Tokyo, pp. 1964-1970, XP002009059.
Shadle et al, "Speech Sythesis by Linear Interpolation of Spectral Parameters Between Dyad Boundaries", The Journal of the Acoustical Society of America, vol. 66, No. 5, Nov. 1979, New York, pp. 1325-1332, XP002009060.
British Telecommunications public limited company
Hudspeth David R.
Lerner Martin
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