Coefficient Clustering - Frequency Domain

The first thing to be done in a more advanced approach is to cluster the masking thresholds in the frequency, so that quantization step sizes do not take too many bits. This is often done in critical bands. This coder uses 24 slightly adjusted critical bands, in each of which the amplitude mean of the masking threshold is used as quantization step size. The bands were adjusted to better use the total clipping which often occurs at high frequencies, due to the ATH.

Band	First bin	Last bin	Coefficient ratio
1	0	1	0.874486
2	2	3	0.810296
3	4	5	0.831361
4	6	7	0.835856
5	8	9	0.894511
6	10	11	0.938870
7	12	13	1.000000
8	14	15	1.000000
9	16	18	1.000000
10	19	21	1.000000
11	22	24	1.000000
12	25	28	1.000000
13	29	33	0.932482
14	34	38	0.962853
15	39	45	0.839628
16	46	53	0.789081
17	54	64	0.685002
18	65	77	0.684814
19	78	91	0.712828
20	92	108	0.683237
21	109	128	0.672980
22	129	149	0.681761
23	150	170	0.818602
24	171	255	0.894698

The table shows the clustering of the frequency bins into bands. The ``Coefficient ratio'' column is described below for stationary coding mode.