In a bid to enhance the search performance, this paper presents an improved version of reduced candidate\nmechanism (RCM), an algebraic code book search conducted on an algebraic code-excited linear prediction (ACELP)\nspeech coder. This improvement is made based on two findings in a piece of our prior work. The first finding is\nthat a pulse with a high contribution in the associated track is more likely to serve as an optimal pulse in the\noptimal code vector and the second is that the speech quality can be well maintained at a search accuracy above\n50% approximately. Subsequently, a new finding in this study concerning a structured algebraic code book in G.729\nindicates that there is a 0.8321 probability that the number 1 ranked pulse in a global sorting by pulse contribution\nis indeed one of the optimal pulses. Hence, the number 1 pulse in the global sorting is labeled as one of the\noptimal pulses, following which a sequence of search tasks are fulfilled through RCM. This proposed complexity\nreduction algorithm, implemented on a G.729A speech codec, takes as few as eight searches, a search load tantamount to 2.5% of G.729A, 12.5% of global pulse replacement method (iterati 16.7% of iteration-free\npulse replacement method, and 50% of RCM (N = 2). This proposal is thus found to successfully reduce the\nrequired computational complexity to a great extent as intended.
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