Abstract: A multi-part fixed codebook includes both individual fixed codebooks for each channel and a shared fixed codebook. Although the shared fixed codebook is common to all channels, the channels are associated with individual lags. Furthermore, the individual fixed codebooks are associated with individual gains, and the individual lags are also associated with individual gains. The excitation from each individual fixed codebook is added to the corresponding excitation (a shared codebook vector, but individual lags and gains for each channel) from the shared fixed codebook.

Abstract: A multi-codebook fixed bitrate CELP signal block encoder/decoder includes a codebook selector (22) for selecting, for each signal block, a corresponding codebook identification in accordance with a deterministic selection procedure that is independent of signal type. Included are also means for encoding/decoding each signal block by using a codebook having the selected codebook identification.

Abstract: A multi-codebook fixed bitrate CELP signal block encoder/decoder includes a codebook selector (22) for selecting, for each signal block, a corresponding codebook identification in accordance with a deterministic selection procedure that is independent of signal type. Included are also means for encoding/decoding each signal block by using a codebook having the selected codebook identification.

Abstract: A multi-codebook fixed bitrate CELP signal block encoder/decoder includes a codebook selector (22) for selecting, for each signal block, a corresponding codebook identification in accordance with a deterministic selection procedure that is independent of signal type. Included are also means for encoding/decoding each signal block by using a codebook having the selected codebook identification.

Abstract: An improved forward error correction (FEC) technique for coding speech data provides an encoder module which primary-encodes an input speech signal using a primary synthesis model to produce primary-encoded data, and redundant-encodes the input speech signal using a redundant synthesis model to produce redundant-encoded data. A packetizer combines the primary-encoded data and the redundant-encoded data into a series of packets and transmits the packets over a packet-based network, such as an Internet Protocol (IP) network. A decoding module primary-decodes the packets using the primary synthesis model, and redundant-decodes the packets using the redundant synthesis model. The technique provides interaction between the primary synthesis model and the redundant synthesis model during and after decoding to improve the quality of a synthesized output speech signal. Such “interaction,” for instance, may take the form of updating states in one model using the other model.

Abstract: A multi-part fixed codebook includes both individual fixed codebooks (FC1, FC2) for each channel and a shared fixed codebook (FCS). Although the shared fixed codebook (FCS) is common to all channels, the channels are associated with individual lags (D1, D2). Furthermore, the individual fixed codebooks (FC1, FC2) are associated with individual gains (gF1, gF2), and the individual lags (D1, D2) are also associated with individual gains (gFS1, gFS2). The excitation from each individual fixed codebook (FS1, FS2) is added to the corresponding excitation (a shared codebook vector, but individual lags and gains for each channel) from the shared fixed codebook (FCS).

Abstract: Perceptually relevant non-speech information can be preserved during encoding of an audio signal by determining whether the audio signal includes such information. If so, a speech/noise classification of the audio signal is overriden to prevent misclassification of the audio signal as noise.

Abstract: In producing an approximation of an original speech signal from encoded information about the original speech signal, current parameters associated with a current segment of the original speech signal are determined from the encoded information. Reproduction of a noise component of the original speech signal is improved by using at least one of the current parameters and corresponding previous parameters respectively associated with previous segments of the original speech signal to produce a modified parameter. The modified parameter is then used to produce an approximation of the current segment of the original speech signal.