Koninklijke Philips Corporation N.V.

U.S. Philips Corporaion

Fransiscus M J De Bont

Friedhelm Wuppermann

In a CELP coder a comparison between a target signal and a plurality of synthetic signals is made. The synthetic signal is derived by filtering a plurality of excitation sequences by a synthesis filter having parameters derived from the target signal. The excitation signal which results in a minimum error between the target signal and the synthetic signal is selected. The search for the best excitation signal requires a substantial computational complexity. To reduce the complexity a preselection of a small number of excitation sequences is made by selecting a small number of excitation sequences resembling the most a backward filtered target signal. With this small number of excitation sequences a full complexity search is made. Due to the reduced number of excitation sequences involved in the final selection the required computational complexity is reduced.

Reduced complexity signal transmission system

In a CELP coder a comparison between a target signal and a plurality of synthetic signals is made. The synthetic signal is derived by filtering a plurality of excitation sequences from a one dimensional codebook by a synthesis filter having parameters derived from the target signal. The excitation signal that results in a minimum error between the target signal and the synthetic signal is selected. In order to reduce the complexity of the search for the best excitation signal, the selection is done in two stages. First a preselection of a small number of excitation sequences is made by selecting only every L.sup.th codebook entry for preselecting a plurality of excitation sequences. Thereafter, with this small number of excitation sequences, a fill complexity search is made in which all excitation sequences surrounding the preselected ones are involved in the selection.

CELP coding with two-stage search over displaced segments of a one-dimensional codebook

In a CELP coder, a comparison between a target signal and a plurality of synthetic signals is made. The synthetic signal is derived by filtering a plurality of excitation sequences by a synthesis filter having parameters derived from the target signal. The excitation signal which results in a minimum error between the target signal and synthetic signal is selected. The search for the best excitation signal requires a substantial computational complexity. To reduce the complexity, a preselection of a small number of excitation sequences is made using a reduced complexity synthesis filter. With this small number of excitation sequences, a full complexity search is made. Due to the reduced number of excitation sequences involved in the final selection, the required computational complexity is reduced.

In a CELP coder, a comparison between a target signal and a plurality of synthetic signals is made. A synthetic signal is derived by filtering a plurality of excitation sequences by a synthesis filter having parameters derived from the target signal. The excitation signal, which results in a minimum error between the target signal and the synthetic signal, is selected. The search for the best excitation signal requires a substantial computational complexity. To reduce the complexity, a preselection of a small number of excitation sequences is made by selecting a small number of excitation sequences resembling the most backward filtered target signal. With this small number of excitation sequences a full complexity search is made. Due to the reduced number of excitation sequences involved in the final selection the required computational complexity is reduced.

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Eindhoven, Netherlands

Fransiscus M J De Bont