elbg.c File Reference

Codebook Generator using the ELBG algorithm. More...

#include <string.h>
#include "libavutil/avassert.h"
#include "libavutil/common.h"
#include "libavutil/lfg.h"
#include "elbg.h"
#include "avcodec.h"

Go to the source code of this file.

Data Structures
struct	cell
	In the ELBG jargon, a cell is the set of points that are closest to a codebook entry. More...
struct	elbg_data
	ELBG internal data. More...

Macros
#define	DELTA_ERR_MAX   0.1
	Precision of the ELBG algorithm (as percentual error)
#define	BIG_PRIME   433494437LL

Functions
static int	distance_limited (int *a, int *b, int dim, int limit)
static void	vect_division (int *res, int *vect, int div, int dim)
static int	eval_error_cell (elbg_data *elbg, int *centroid, cell *cells)
static int	get_closest_codebook (elbg_data *elbg, int index)
static int	get_high_utility_cell (elbg_data *elbg)
static int	simple_lbg (elbg_data *elbg, int dim, int *centroid[3], int newutility[3], int *points, cell *cells)
	Implementation of the simple LBG algorithm for just two codebooks.
static void	get_new_centroids (elbg_data *elbg, int huc, int *newcentroid_i, int *newcentroid_p)
static void	shift_codebook (elbg_data *elbg, int *indexes, int *newcentroid[3])
	Add the points in the low utility cell to its closest cell.
static void	evaluate_utility_inc (elbg_data *elbg)
static void	update_utility_and_n_cb (elbg_data *elbg, int idx, int newutility)
static void	try_shift_candidate (elbg_data *elbg, int idx[3])
	Evaluate if a shift lower the error.
static void	do_shiftings (elbg_data *elbg)
	Implementation of the ELBG block.
void	avpriv_init_elbg (int *points, int dim, int numpoints, int *codebook, int numCB, int max_steps, int *closest_cb, AVLFG *rand_state)
	Initialize the **codebook vector for the elbg algorithm.
void	avpriv_do_elbg (int *points, int dim, int numpoints, int *codebook, int numCB, int max_steps, int *closest_cb, AVLFG *rand_state)
	Implementation of the Enhanced LBG Algorithm Based on the paper "Neural Networks 14:1219-1237" that can be found in http://citeseer.ist.psu.edu/patan01enhanced.html .

Detailed Description

Codebook Generator using the ELBG algorithm.

Definition in file elbg.c.

Macro Definition Documentation

#define DELTA_ERR_MAX   0.1

Precision of the ELBG algorithm (as percentual error)

Definition at line 34 of file elbg.c.

Referenced by avpriv_do_elbg().

#define BIG_PRIME   433494437LL

Definition at line 325 of file elbg.c.

Referenced by avpriv_init_elbg().

Function Documentation

static int distance_limited ( int *  a, int *  b, int  dim, int  limit  )

inlinestatic

Definition at line 61 of file elbg.c.

Referenced by avpriv_do_elbg(), eval_error_cell(), get_closest_codebook(), shift_codebook(), and simple_lbg().

static void vect_division ( int *  res, int *  vect, int  div, int  dim  )

inlinestatic

Definition at line 73 of file elbg.c.

Referenced by avpriv_do_elbg(), simple_lbg(), and try_shift_candidate().

static int eval_error_cell ( elbg_data *  elbg, int *  centroid, cell *  cells  )

static

Definition at line 84 of file elbg.c.

Referenced by try_shift_candidate().

static int get_closest_codebook ( elbg_data *  elbg, int  index  )

static

Definition at line 93 of file elbg.c.

Referenced by do_shiftings().

static int get_high_utility_cell ( elbg_data *  elbg )

static

Definition at line 107 of file elbg.c.

Referenced by do_shiftings().

static int simple_lbg ( elbg_data *  elbg, int  dim, int *  centroid[3], int  newutility[3], int *  points, cell *  cells  )

static

Implementation of the simple LBG algorithm for just two codebooks.

Definition at line 123 of file elbg.c.

Referenced by try_shift_candidate().

static void get_new_centroids ( elbg_data *  elbg, int  huc, int *  newcentroid_i, int *  newcentroid_p  )

static

Definition at line 164 of file elbg.c.

Referenced by try_shift_candidate().

static void shift_codebook ( elbg_data *  elbg, int *  indexes, int *  newcentroid[3]  )

static

Add the points in the low utility cell to its closest cell.

Split the high utility cell, putting the separate points in the (now empty) low utility cell.

Parameters

elbg	Internal elbg data
indexes	{luc, huc, cluc}
newcentroid	A vector with the position of the new centroids

Definition at line 200 of file elbg.c.

Referenced by try_shift_candidate().

static void evaluate_utility_inc ( elbg_data *  elbg )

static

Definition at line 228 of file elbg.c.

Referenced by do_shiftings(), and try_shift_candidate().

static void update_utility_and_n_cb ( elbg_data *  elbg, int  idx, int  newutility  )

static

Definition at line 240 of file elbg.c.

Referenced by try_shift_candidate().

static void try_shift_candidate ( elbg_data *  elbg, int  idx[3]  )

static

Evaluate if a shift lower the error.

If it does, call shift_codebooks and update elbg->error, elbg->utility and elbg->nearest_cb.

Parameters

elbg	Internal elbg data
idx	{luc (low utility cell, huc (high utility cell), cluc (closest cell to low utility cell)}

Definition at line 256 of file elbg.c.

Referenced by do_shiftings().

static void do_shiftings ( elbg_data *  elbg )

static

Implementation of the ELBG block.

Definition at line 306 of file elbg.c.

Referenced by avpriv_do_elbg().

void avpriv_init_elbg	(	int *	points,
		int	dim,
		int	numpoints,
		int *	codebook,
		int	numCB,
		int	num_steps,
		int *	closest_cb,
		AVLFG *	rand_state
	)

Initialize the **codebook vector for the elbg algorithm.

If you have already a codebook and you want to refine it, you shouldn't call this function. If numpoints < 8*numCB this function fills **codebook with random numbers. If not, it calls avpriv_do_elbg for a (smaller) random sample of the points in **points. Get the same parameters as avpriv_do_elbg.

Definition at line 327 of file elbg.c.

Referenced by a64multi_encode_frame(), avpriv_init_elbg(), encode_frame(), filter_frame(), generate_codebook(), and quantize().

void avpriv_do_elbg	(	int *	points,
		int	dim,
		int	numpoints,
		int *	codebook,
		int	numCB,
		int	num_steps,
		int *	closest_cb,
		AVLFG *	rand_state
	)

Implementation of the Enhanced LBG Algorithm Based on the paper "Neural Networks 14:1219-1237" that can be found in http://citeseer.ist.psu.edu/patan01enhanced.html .

Parameters

points	Input points.
dim	Dimension of the points.
numpoints	Num of points in **points.
codebook	Pointer to the output codebook. Must be allocated.
numCB	Number of points in the codebook.
num_steps	The maximum number of steps. One step is already a good compromise between time and quality.
closest_cb	Return the closest codebook to each point. Must be allocated.
rand_state	A random number generator state. Should be already initialized by av_lfg_init().

Definition at line 354 of file elbg.c.

Referenced by a64multi_encode_frame(), avpriv_init_elbg(), encode_frame(), filter_frame(), generate_codebook(), and quantize().