Efficient Search in the Adaptive Codebook for ITU-T G.729 Codec

This paper describes computationally efficient implementations for the ITU-T G.729 speech codec. Focus is given to the adaptive codebook search, more specifically in the open-loop stage, which first estimates the pitch period of the speech frame being coded. Different strategies are discussed to achieve an excellent compromise between computational complexity and signal quality. The result is an accelerated procedure for the G.729 and G.729A versions, reducing encoding time in about 12% and 9%, respectively, while sustaining original signal quality, as verified by objective and subjective measurements.