Abstract: System and method embodiments for dual modes pitch coding are provided. The system and method embodiments are configured to adaptively code pitch lags of a voiced speech signal using one of two pitch coding modes according to a pitch length, stability, or both. The two pitch coding modes include a first pitch coding mode with relatively high precision and reduced dynamic range, and a second pitch coding mode with relatively large dynamic range and reduced precision. The first pitch coding mode is used upon determining that the voiced speech signal has a relatively short or substantially stable pitch. The second pitch coding mode is used upon determining that the voiced speech signal has a relatively long or less stable pitch or is a substantially noisy signal.

Abstract: Systems and method for managing and/or mitigating the impact of bit errors on encoded frames received by an LC-SBC (Low Complexity Sub-band Coding) decoder are described herein. For example, in one embodiment, the impact of bit errors on an LC-SBC frame received by an LC-SBC decoder is estimated and one of a plurality of bit error management techniques is applied to the LC-SBC frame based on the estimated impact, wherein the bit error management techniques may include performing PLC, performing normal SBC decoding, or performing some other technique for managing and/or mitigating the impact of the bit errors. Techniques for concealing bit errors in LC-SBC frames are also described.

Abstract: Provided is a method for converting a dimension of a vector. The vector dimension conversion method for vector quantization includes the steps of: extracting a specific parameter having a pitch period from an input speech signal and then generating a vector of a dimension that varies according to the pitch period; dividing an entire frequency domain of the generated vector of the variable dimension into at least two frequency domains; and converting the vector of the variable dimension into vectors of mutually different fixed dimensions according to the divided frequency domains. Thereby, not only an error due to the vector dimension conversion is suppressed but codebook memory required for the vector quantization is effectively reduced.

Abstract: Various strategies for rate/quality control and loss resiliency in an audio codec are described. The various strategies can be used in combination or independently. For example, a real-time speech codec uses intra frame coding/decoding, adaptive multi-mode forward error correction [“FEC”], and rate/quality control techniques. Intra frames help a decoder recover quickly from packet losses, while compression efficiency is still emphasized with predicted frames. Various strategies for inserting intra frames and signaling intra/predicted frames are described. With the adaptive multi-mode FEC, an encoder adaptively selects between multiple modes to efficiently and quickly provide a level of FEC that takes into account the bandwidth currently available for FEC. The FEC information itself may be predictively encoded and decoded relative to primary encoded information. Various rate/quality and FEC control strategies allow additional adaptation to available bandwidth and network conditions.

Abstract: A pitch-estimation method, a pitch-estimation system, and a pitch-estimation program are provided, which estimate a weight of a probability density function of a fundamental frequency and relative amplitude of a harmonic component through fewer computations than ever. In the improved pitch-estimation method, 1200 log2 h and exp[?(x?(F+1200 log2 h))2/2W2] in the following expression are computed in advance and then stored in a memory of a computer: c ? ? ( t ) ? ( h ? F , m ) ? 1 2 ? ? ? ? W 2 ? exp ( - ( x - ( F + 1200 ? ? log 2 ? h ) ) 2 2 ? W 2 ) ( 61 ) The above expression is computed only with respect to a fundamental frequency F wherein x?(F+1200 log2 h) is close to zero. With this arrangement, computations to be performed may considerably be reduced, and computing time may accordingly be shortened.