libavcodec/lsp.c File Reference

#include <inttypes.h>
#include "avcodec.h"
#include "mathops.h"
#include "lsp.h"
#include "celp_math.h"

Go to the source code of this file.

Defines
#define	FRAC_BITS   14
Functions
void	ff_acelp_reorder_lsf (int16_t *lsfq, int lsfq_min_distance, int lsfq_min, int lsfq_max, int lp_order)
	(I.F) means fixed-point value with F fractional and I integer bits
void	ff_set_min_dist_lsf (float *lsf, double min_spacing, int size)
	Adjust the quantized LSFs so they are increasing and not too close.
void	ff_acelp_lsf2lsp (int16_t *lsp, const int16_t *lsf, int lp_order)
	Convert LSF to LSP.
static void	lsp2poly (int *f, const int16_t *lsp, int lp_half_order)
	decodes polynomial coefficients from LSP
void	ff_acelp_lsp2lpc (int16_t *lp, const int16_t *lsp, int lp_half_order)
	LSP to LP conversion (3.2.6 of G.729).
void	ff_acelp_lp_decode (int16_t *lp_1st, int16_t *lp_2nd, const int16_t *lsp_2nd, const int16_t *lsp_prev, int lp_order)
	Interpolate LSP for the first subframe and convert LSP -> LP for both subframes (3.2.5 and 3.2.6 of G.729).
void	ff_lsp2polyf (const double *lsp, 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_acelp_lspd2lpc (const double *lsp, float *lpc, int lp_half_order)
	Reconstructs LPC coefficients from the line spectral pair frequencies.
void	ff_sort_nearly_sorted_floats (float *vals, int len)
	Sort values in ascending order.

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Define Documentation

#define FRAC_BITS   14

Definition at line 27 of file lsp.c.

Referenced by add_yblock(), compute_stereo(), decode_frame(), decode_init(), ff_snow_inner_add_yblock(), gen_image(), imdct36(), int_cos(), lsp2poly(), main(), mpegaudio_tableinit(), predict_slice(), predict_slice_buffered(), swf_write_header(), and swf_write_video().

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Function Documentation

void ff_acelp_lp_decode	(	int16_t *	lp_1st,
		int16_t *	lp_2nd,
		const int16_t *	lsp_2nd,
		const int16_t *	lsp_prev,
		int	lp_order
	)

Interpolate LSP for the first subframe and convert LSP -> LP for both subframes (3.2.5 and 3.2.6 of G.729).

Parameters:

	lp_1st	[out] decoded LP coefficients for first subframe (-0x8000 <= (3.12) < 0x8000)
	lp_2nd	[out] decoded LP coefficients for second subframe (-0x8000 <= (3.12) < 0x8000)
	lsp_2nd	LSP coefficients of the second subframe (-0x8000 <= (0.15) < 0x8000)
	lsp_prev	LSP coefficients from the second subframe of the previous frame (-0x8000 <= (0.15) < 0x8000)
	lp_order	LP filter order

Definition at line 112 of file lsp.c.

Referenced by decode_frame().

void ff_acelp_lsf2lsp	(	int16_t *	lsp,
		const int16_t *	lsf,
		int	lp_order
	)

Convert LSF to LSP.

Parameters:

	lsp	[out] LSP coefficients (-0x8000 <= (0.15) < 0x8000)
	lsf	normalized LSF coefficients (0 <= (2.13) < 0x2000 * PI)
	lp_order	LP filter order

Remarks:

It is safe to pass the same array into the lsf and lsp parameters.

Definition at line 58 of file lsp.c.

Referenced by decode_frame().

void ff_acelp_lsp2lpc	(	int16_t *	lp,
		const int16_t *	lsp,
		int	lp_half_order
	)

LSP to LP conversion (3.2.6 of G.729).

Parameters:

	lp	[out] decoded LP coefficients (-0x8000 <= (3.12) < 0x8000)
	lsp	LSP coefficients (-0x8000 <= (0.15) < 0x8000)
	lp_half_order	LP filter order, divided by 2

Definition at line 90 of file lsp.c.

Referenced by ff_acelp_lp_decode().

void ff_acelp_lspd2lpc	(	const double *	lsp,
		float *	lpc,
		int	lp_half_order
	)

Reconstructs LPC coefficients from the line spectral pair frequencies.

Parameters:

	lsp	line spectral pairs in cosine domain
	lpc	linear predictive coding coefficients
	lp_half_order	half the number of the amount of LPCs to be reconstructed, need to be smaller or equal to MAX_LP_HALF_ORDER

Note:

buffers should have a minimux size of 2*lp_half_order elements.

TIA/EIA/IS-733 2.4.3.3.5

Definition at line 148 of file lsp.c.

Referenced by acelp_lp_decodef(), amrnb_decode_frame(), lspf2lpc(), synth_block(), and synth_frame().

void ff_acelp_reorder_lsf	(	int16_t *	lsfq,
		int	lsfq_min_distance,
		int	lsfq_min,
		int	lsfq_max,
		int	lp_order
	)

(I.F) means fixed-point value with F fractional and I integer bits

ensure a minimum distance between LSFs

Parameters:

	lsfq	[in/out] LSF to check and adjust
	lsfq_min_distance	minimum distance between LSFs
	lsfq_min	minimum allowed LSF value
	lsfq_max	maximum allowed LSF value
	lp_order	LP filter order

Definition at line 32 of file lsp.c.

Referenced by lsf_decode().

void ff_lsp2polyf	(	const double *	lsp,
		double *	f,
		int	lp_half_order
	)

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:

	lsp	line spectral pairs in cosine domain
	f	[out] polynomial input/output as a vector

TIA/EIA/IS-733 2.4.3.3.5-1/2

Definition at line 131 of file lsp.c.

Referenced by ff_acelp_lspd2lpc(), and lsp2lpc_sipr().

void ff_set_min_dist_lsf	(	float *	lsf,
		double	min_spacing,
		int	order
	)

Adjust the quantized LSFs so they are increasing and not too close.

This step is not mentioned in the AMR spec but is in the reference C decoder. Omitting this step creates audible distortion on the sinusoidal sweep test vectors in 3GPP TS 26.074.

Parameters:

[in,out]	lsf	LSFs in Hertz
	min_spacing	minimum distance between two consecutive lsf values
	size	size of the lsf vector

Definition at line 50 of file lsp.c.

Referenced by ff_sipr_decode_frame_16k(), lsf2lsp_3(), lsf2lsp_for_mode12k2(), and lsf_decode_fp().

void ff_sort_nearly_sorted_floats	(	float *	vals,
		int	len
	)

Sort values in ascending order.

Note:

O(n) if data already sorted, O(n^2) - otherwise

Definition at line 167 of file lsp.c.

Referenced by decode_lsp(), and lsf_decode_fp().

static void lsp2poly	(	int *	f,
		const int16_t *	lsp,
		int	lp_half_order
	)			[static]

decodes polynomial coefficients from LSP

Parameters:

	f	[out] decoded polynomial coefficients (-0x20000000 <= (3.22) <= 0x1fffffff)
	lsp	LSP coefficients (-0x8000 <= (0.15) <= 0x7fff)

Definition at line 73 of file lsp.c.

Referenced by ff_acelp_lsp2lpc().