libavcodec/qcelp_lsp.c File Reference

QCELP decoder. More...

#include "libavutil/mathematics.h"

Go to the source code of this file.

Defines

#define QCELP_BANDWITH_EXPANSION_COEFF   0.9883
 initial coefficient to perform bandwidth expansion on LPC

Functions

static void lsp2polyf (const float *lspf, double *f, int lp_half_order)
 Computes the Pa / (1 + z(-1)) or Qa / (1 - z(-1)) coefficients needed for LSP to LPC conversion.
void ff_qcelp_lspf2lpc (const float *lspf, float *lpc)
 Reconstructs LPC coefficients from the line spectral pair frequencies and performs bandwidth expansion.


Detailed Description

QCELP decoder.

Author:
Reynaldo H. Verdejo Pinochet
Remarks:
FFmpeg merging spearheaded by Kenan Gillet

Development mentored by Benjamin Larson

Definition in file qcelp_lsp.c.


Define Documentation

#define QCELP_BANDWITH_EXPANSION_COEFF   0.9883

initial coefficient to perform bandwidth expansion on LPC

Note:
: 0.9883 looks like an approximation of 253/256.
TIA/EIA/IS-733 2.4.3.3.6 6

Definition at line 39 of file qcelp_lsp.c.

Referenced by ff_qcelp_lspf2lpc().


Function Documentation

void ff_qcelp_lspf2lpc ( const float *  lspf,
float *  lpc 
)

Reconstructs LPC coefficients from the line spectral pair frequencies and performs bandwidth expansion.

Reconstructs LPC coefficients from the line spectral pair frequencies.

Parameters:
lspf line spectral pair frequencies
lpc linear predictive coding coefficients
Note:
: bandwith_expansion_coeff could be precalculated into a table but it seems to be slower on x86
TIA/EIA/IS-733 2.4.3.3.5

Definition at line 80 of file qcelp_lsp.c.

Referenced by interpolate_lpc().

static void lsp2polyf ( const float *  lspf,
double *  f,
int  lp_half_order 
) [static]

Computes the Pa / (1 + z(-1)) or Qa / (1 - z(-1)) coefficients needed for LSP to LPC conversion.

We only need to calculate the 6 first elements of the polynomial.

Parameters:
lspf line spectral pair frequencies
f [out] polynomial input/output as a vector
TIA/EIA/IS-733 2.4.3.3.5-1/2

Definition at line 51 of file qcelp_lsp.c.

Referenced by ff_qcelp_lspf2lpc().


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