#include <inttypes.h>
#include "avcodec.h"
#include "acelp_filters.h"
Go to the source code of this file.
Functions | |
void | ff_acelp_interpolate (int16_t *out, const int16_t *in, const int16_t *filter_coeffs, int precision, int frac_pos, int filter_length, int length) |
Generic FIR interpolation routine. | |
void | ff_acelp_high_pass_filter (int16_t *out, int hpf_f[2], const int16_t *in, int length) |
high-pass filtering and upscaling (4.2.5 of G.729). | |
Variables | |
const int16_t | ff_acelp_interp_filter [61] |
low-pass Finite Impulse Response filter coefficients. |
void ff_acelp_high_pass_filter | ( | int16_t * | out, | |
int | hpf_f[2], | |||
const int16_t * | in, | |||
int | length | |||
) |
high-pass filtering and upscaling (4.2.5 of G.729).
out | [out] output buffer for filtered speech data | |
hpf_f | [in/out] past filtered data from previous (2 items long) frames (-0x20000000 <= (14.13) < 0x20000000) | |
in | speech data to process | |
length | input data size |
The filter has a cut-off frequency of 1/80 of the sampling freq
AMR uses mostly the same filter (cut-off frequency 60Hz, same formula, but constants differs in 5th sign after comma). Fortunately in fixed-point all coefficients are the same as in G.729. Thus this routine can be used for the fixed-point AMR decoder, too.
Definition at line 85 of file acelp_filters.c.
void ff_acelp_interpolate | ( | int16_t * | out, | |
const int16_t * | in, | |||
const int16_t * | filter_coeffs, | |||
int | precision, | |||
int | frac_pos, | |||
int | filter_length, | |||
int | length | |||
) |
Generic FIR interpolation routine.
out | [out] buffer for interpolated data | |
in | input data | |
filter_coeffs | interpolation filter coefficients (0.15) | |
precision | sub sample factor, that is the precision of the position | |
frac_pos | fractional part of position [0..precision-1] | |
filter_length | filter length | |
length | length of output |
Definition at line 43 of file acelp_filters.c.
const int16_t ff_acelp_interp_filter[61] |
Initial value:
{ 29443, 28346, 25207, 20449, 14701, 8693, 3143, -1352, -4402, -5865, -5850, -4673, -2783, -672, 1211, 2536, 3130, 2991, 2259, 1170, 0, -1001, -1652, -1868, -1666, -1147, -464, 218, 756, 1060, 1099, 904, 550, 135, -245, -514, -634, -602, -451, -231, 0, 191, 308, 340, 296, 198, 78, -36, -120, -163, -165, -132, -79, -19, 34, 73, 91, 89, 70, 38, 0, }
Hamming windowed sinc filter with cutoff freq 3/40 of the sampling freq, the coefficients are scaled by 2^15. This array only contains the right half of the filter. This filter is likely identical to the one used in G.729, though this could not be determined from the original comments with certainity.
Definition at line 28 of file acelp_filters.c.