A structured codebook and subsequent analyses were developed, guided by grounded theory [ 23, 24].
We consider an image in the overcomplete transform domain as a realization of a random source with a structured codebook of symbols where each symbol represents a particular edge shape.
Assuming that there are Nt tracks in a structured algebraic codebook, out of which Np pulses must be selected in each codebook search, then the respective numbers of searches required in RCM and this presented Fixed-G1-RCM searching approaches are given as Searches RCM, N = C Np N Nt = N !
Taking a structured algebraic codebook in G.729 as an instance (Nt = 4, Np = 1), this proposal requires N3 searches, while RCM requires as many as N4 searches.
Subsequently, a new finding in this study concerning a structured algebraic codebook in G.729 indicates that there is a 0.8321 probability that the number 1 ranked pulse in a global sorting by pulse contribution is indeed one of the optimal pulses.
To further improve the performance, a cluster-structured codebook is developed by clustering together the codewords with high correlation[31, 32].
Figure 7 shows the results of the MOS subjective quality test [32] at three different rates exploiting a tree-structured codebook identical to the one used in PESQ tests using a full search for choosing codewords.
Following the idea of area classification, next we consider a cluster-structured codebook-based coordinated beamforming and design an area-specific limited feedback.
The tree-like structured codebooks of our embedded quantizer, constructed through a cell merging process, help to make a fine-grain scalable speech coder.
By decreasing one bit, we select a codeword from a lower depth stage of the tree-structured codebook.
