[vorbis-dev] floor0.c and lsp.c optimisations

TIMMERMANS ANDRE Andre.Timmermans at sbs.be
Wed Sep 11 00:04:32 PDT 2002


I think that the introduction of the lsp_look lookup array
isn't ideal and found a better change that can be applied.

in floor0_map_lazy_init() you can replace




and in vorbis_lsp_to_curve you then replace

float w=vorbis_coslook(wdel*k);


float w=map[i];

then get rid of the ln function parameter and the k local variable.

<p><p>Next the fact that p and q are initialised to 1/sqrt(2),
multiplied by a series of factors and finally squared
means that on exit the 1/sqrt(2) becomes a 1/2 factor
and me think that there are some multiplications
that can be spared in the process by doing

float p=lsp[0]-w;
float q=lsp[1]-w;
int c=(m>>1)-1;

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