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Part 1 of 2 of Kenan Gillet's 'make ff_qcelp_lspf2lpc

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more general' changeset. This one splits ff_qcelp_lspf2lpc
into the QCELP-especific ff_qcelp_lspf2lpc + the more general
ff_qcelp_lspf2lpc.

Originally committed as revision 17799 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Reynaldo H. Verdejo Pinochet 2009-03-04 01:28:07 +00:00
parent e1374c06d6
commit 77bd18e117
1 changed files with 32 additions and 14 deletions
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46
libavcodec/qcelp_lsp.c
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@ -48,16 +48,16 @@
*
* TIA/EIA/IS-733 2.4.3.3.5-1/2
*/
static void lsp2polyf(const float *lspf, double *f, int lp_half_order)
static void lsp2polyf(const double *lspf, double *f, int lp_half_order)
{
int i, j;
f[0] = 1.0;
f[1] = -2 * cos(M_PI * lspf[0]);
f[1] = -2 * lspf[0];
lspf -= 2;
for(i=2; i<=lp_half_order; i++)
{
double val = -2 * cos(M_PI * lspf[2*i]);
double val = -2 * lspf[2*i];
f[i] = val * f[i-1] + 2*f[i-2];
for(j=i-1; j>1; j--)
f[j] += f[j-1] * val + f[j-2];
@ -65,6 +65,30 @@ static void lsp2polyf(const float *lspf, double *f, int lp_half_order)
}
}
/**
* Reconstructs LPC coefficients from the line spectral pair frequencies.
*
* @param lspf line spectral pair frequencies
* @param lpc linear predictive coding coefficients
*/
void ff_celp_lspf2lpc(const double *lspf, float *lpc)
{
double pa[6], qa[6];
int i;
lsp2polyf(lspf, pa, 5);
lsp2polyf(lspf + 1, qa, 5);
for (i=4; i>=0; i--)
{
double paf = pa[i+1] + pa[i];
double qaf = qa[i+1] - qa[i];
lpc[i ] = 0.5 * (paf+qaf);
lpc[9-i] = 0.5 * (paf-qaf);
}
}
/**
* Reconstructs LPC coefficients from the line spectral pair frequencies
* and performs bandwidth expansion.
@ -79,21 +103,15 @@ static void lsp2polyf(const float *lspf, double *f, int lp_half_order)
*/
void ff_qcelp_lspf2lpc(const float *lspf, float *lpc)
{
double pa[6], qa[6];
double lsf[10];
double bandwith_expansion_coeff = QCELP_BANDWITH_EXPANSION_COEFF;
int i;
double bandwith_expansion_coeff = QCELP_BANDWITH_EXPANSION_COEFF * 0.5;
lsp2polyf(lspf, pa, 5);
lsp2polyf(lspf + 1, qa, 5);
for (i=0; i<10; i++)
lsf[i] = cos(M_PI * lspf[i]);
for (i=4; i>=0; i--)
{
double paf = pa[i+1] + pa[i];
double qaf = qa[i+1] - qa[i];
ff_celp_lspf2lpc(lsf, lpc);
lpc[i ] = paf + qaf;
lpc[9-i] = paf - qaf;
}
for (i=0; i<10; i++)
{
lpc[i] *= bandwith_expansion_coeff;