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lpc: add ff_lpc_calc_ref_coefs_f() function

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This commit adds a function to get the reflection coefficients on
floating point samples. It's functionally identical to
ff_lpc_calc_ref_coefs() except it works on float samples and will
return the global prediction gain. The Welch window implementation
which is more optimized works only on int32_t samples so a slower
generic expression was used.

Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>
This commit is contained in:
Rostislav Pehlivanov 2015-09-01 06:34:50 +01:00
parent a70ee2bdcd
commit 0fc3a51353
2 changed files with 22 additions and 0 deletions
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20
libavcodec/lpc.c
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@ -167,6 +167,26 @@ int ff_lpc_calc_ref_coefs(LPCContext *s,
return order;
}
double ff_lpc_calc_ref_coefs_f(LPCContext *s, const float *samples, int len,
int order, double *ref)
{
int i;
double signal = 0.0f, avg_err = 0.0f;
double autoc[MAX_LPC_ORDER+1] = {0}, error[MAX_LPC_ORDER] = {0};
const double c = (len - 1)/2.0f;
/* Welch window */
for (i = 0; i < len; i++)
s->windowed_samples[i] = 1.0f - ((samples[i]-c)/c)*((samples[i]-c)/c);
s->lpc_compute_autocorr(s->windowed_samples, len, order, autoc);
signal = autoc[0];
compute_ref_coefs(autoc, order, ref, error);
for (i = 0; i < order; i++)
avg_err = (avg_err + error[i])/2.0f;
return signal/avg_err;
}
/**
* Calculate LPC coefficients for multiple orders
*

2
libavcodec/lpc.h
View File

@ -100,6 +100,8 @@ int ff_lpc_calc_coefs(LPCContext *s,
int ff_lpc_calc_ref_coefs(LPCContext *s,
const int32_t *samples, int order, double *ref);
double ff_lpc_calc_ref_coefs_f(LPCContext *s, const float *samples, int len,
int order, double *ref);
/**
* Initialize LPCContext.