System for improved use of pitch enhancement with subcodebooks
First Claim
1. A method of pitch enhancement in a speech compression system, the method comprising:
- providing a fixed codebook comprising at least two fixed subcodebooks;
selecting one of the at least two fixed subcodebooks;
calculating a pitch enhancement coefficient dependent upon the one of the at least two fixed subcodebooks;
applying a pitch enhancement in response to the pitch enhancement coefficient and the one of the at least two fixed subcodebooks;
where the pitch enhancement is applied both forward and backward, where the pitch enhancement coefficient is applied to pulses selected from the group consisting of forward, backward, and forward and backward pitch pulses, of a main pulse, and where the pitch enhancement coefficient is applied to a first power for pulses one pitch lag away from the main pulse, and the pitch enhancement coefficient is applied to a second power for pulses two pitch lags away from the main pulse.
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Abstract
A speech compression system capable of encoding a speech signal into a bitstream for subsequent decoding to generate synthesized speech is disclosed. The speech compression system optimizes the bandwidth consumed by the bitstream by balancing the desired average bit rate with the perceptual quality of the reconstructed speech. The speech compression system comprises a full-rate codec, a half-rate codec, a quarter-rate codec and an eighth-rate codec. The codecs are selectively activated based on a rate selection. In addition, the full and half-rate codec are selectively activated based on a type classification. Each codec is selectively activated to encode and decode the speech signals at different bit rates emphasizing different aspects of the speech signal to enhance overall quality of the synthesized speech. The overall quality of the system is strongly related to the excitation. In order to enhance the excitation, the system contains a fixed codebook comprising several subcodebooks. The invention reveals a way to apply a pitch enhancement efficiently and differently for different subcodebooks without using additional bits. The technique is particularly applicable to selectable mode vocoder (SMV) systems.
41 Citations
34 Claims
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1. A method of pitch enhancement in a speech compression system, the method comprising:
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providing a fixed codebook comprising at least two fixed subcodebooks; selecting one of the at least two fixed subcodebooks; calculating a pitch enhancement coefficient dependent upon the one of the at least two fixed subcodebooks; applying a pitch enhancement in response to the pitch enhancement coefficient and the one of the at least two fixed subcodebooks; where the pitch enhancement is applied both forward and backward, where the pitch enhancement coefficient is applied to pulses selected from the group consisting of forward, backward, and forward and backward pitch pulses, of a main pulse, and where the pitch enhancement coefficient is applied to a first power for pulses one pitch lag away from the main pulse, and the pitch enhancement coefficient is applied to a second power for pulses two pitch lags away from the main pulse. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A speech coding system comprising:
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a pitch enhancement coefficient; a fixed codebook comprising at least two fixed subcodebooks; and a pitch enhancement based on the pitch enhancement coefficient and the one of the at least two fixed subcodebooks, wherein the pitch enhancement coefficient is dependent on the selected fixed subcodebook, where the pitch enhancement is applied forward and backward; where the pitch enhancement coefficient is applied to pulses selected from the group consisting of forward, backward, and forward and backward pitch pulses of a main pulse; where the pitch enhancement coefficient is applied to a first power for pulses one pitch lag away from the main pulse, and the pitch enhancement coefficient is applied to a second power for pulses two pitch lags away from the main pulse. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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Specification