Abstract: A Yule-Walker based, low-complexity voice activity detector (VAD) is disclosed. An input signal is typically noisy speech (i.e., corrupted with, for example, babble noise). In one embodiment, a first initialization stage of the VAD computes an occurrence of a silent period within the input signal and the AR parameters. The VAD could accordingly compute a tentative adaptive threshold and output hypothesis H1 (which means speech is present) during this stage. During the second initialization stage, the VAD generally builds a database of associated values and computes the adaptive threshold accordingly. The second initialization stage could also output tentative VAD decisions based on the tentative threshold computed in the first initialization stage. Finally, the VAD periodically retrains or updates AR parameters, threshold values and/or the database and outputs VAD decisions accordingly.

Abstract: A method for performing a search of a codebook is provided. The codebook includes a plurality of tracks each having a plurality of even pulse positions. The method includes partitioning a codevector having a plurality of pulses into a first subset of pulses and a second subset of pulses. Each pulse is assignable to a pulse position in the codevector, and each pulse is associated with a shift bit for indicating an odd position. The method also includes performing a first search for determining a first set of possible pulse positions for the pulses in the codevector. The method further includes performing a second search for determining a second set of possible pulse positions for the pulses in the codevector. In addition, the method includes forming the codevector using the first and second sets of possible pulse positions.