quant_mpeg4.c

mpeg4代码,比较具体

/*****************************************************************************
 *
 *  XVID MPEG-4 VIDEO CODEC
 *  - Mpeg4 quantization/dequantization functions -
 *
 *  Copyright(C) 2002 Peter Ross <[e-mail]>
 *
 *  This file is part of XviD, a free MPEG-4 video encoder/decoder
 *
 *  XviD is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 *  Under section 8 of the GNU General Public License, the copyright
 *  holders of XVID explicitly forbid distribution in the following
 *  countries:
 *
 *    - Japan
 *    - United States of America
 *
 *  Linking XviD statically or dynamically with other modules is making a
 *  combined work based on XviD.  Thus, the terms and conditions of the
 *  GNU General Public License cover the whole combination.
 *
 *  As a special exception, the copyright holders of XviD give you
 *  permission to link XviD with independent modules that communicate with
 *  XviD solely through the VFW1.1 and DShow interfaces, regardless of the
 *  license terms of these independent modules, and to copy and distribute
 *  the resulting combined work under terms of your choice, provided that
 *  every copy of the combined work is accompanied by a complete copy of
 *  the source code of XviD (the version of XviD used to produce the
 *  combined work), being distributed under the terms of the GNU General
 *  Public License plus this exception.  An independent module is a module
 *  which is not derived from or based on XviD.
 *
 *  Note that people who make modified versions of XviD are not obligated
 *  to grant this special exception for their modified versions; it is
 *  their choice whether to do so.  The GNU General Public License gives
 *  permission to release a modified version without this exception; this
 *  exception also makes it possible to release a modified version which
 *  carries forward this exception.
 *
 * $Id: quant_mpeg4.c,v 1.8 2002/12/15 01:21:12 edgomez Exp $
 *
 ****************************************************************************/

#include "quant_mpeg4.h"
#include "quant_matrix.h"

/*****************************************************************************
 * Function pointers
 ****************************************************************************/

quant_intraFuncPtr quant4_intra;
quant_intraFuncPtr dequant4_intra;
dequant_interFuncPtr dequant4_inter;
quant_interFuncPtr quant4_inter;


/*****************************************************************************
 * Local data
 ****************************************************************************/

#define DIV_DIV(A,B)    ( (A) > 0 ? ((A)+((B)>>1))/(B) : ((A)-((B)>>1))/(B) )
#define SIGN(A)  ((A)>0?1:-1)
#define VM18P    3
#define VM18Q    4


/*
 * divide-by-multiply table
 * need 17 bit shift (16 causes slight errors when q > 19)
 */

#define SCALEBITS    17
#define FIX(X)        ((1UL << SCALEBITS) / (X) + 1)

static const uint32_t multipliers[32] = {
	0, FIX(2), FIX(4), FIX(6),
	FIX(8), FIX(10), FIX(12), FIX(14),
	FIX(16), FIX(18), FIX(20), FIX(22),
	FIX(24), FIX(26), FIX(28), FIX(30),
	FIX(32), FIX(34), FIX(36), FIX(38),
	FIX(40), FIX(42), FIX(44), FIX(46),
	FIX(48), FIX(50), FIX(52), FIX(54),
	FIX(56), FIX(58), FIX(60), FIX(62)
};

/*****************************************************************************
 * Functions
 ****************************************************************************/

#if	0
/*    quantize intra-block	*/

    // const int32_t quantd = DIV_DIV(VM18P*quant, VM18Q);
    //
    // level = DIV_DIV(16 * data[i], default_intra_matrix[i]);
    // coeff[i] = (level + quantd) / quant2;
#endif

void
quant4_intra_c(int16_t * coeff,
			   const int16_t * data,
			   const uint32_t quant,
			   const uint32_t dcscalar)
{
	const uint32_t quantd = ((VM18P * quant) + (VM18Q / 2)) / VM18Q;
	const uint32_t mult = multipliers[quant];
	uint32_t i;
	int16_t *intra_matrix;

	intra_matrix = get_intra_matrix();

	coeff[0] = (int16_t)(DIV_DIV(data[0], (int32_t) dcscalar));

	for (i = 1; i < 64; i++) {
		if (data[i] < 0) {
			uint32_t level = -data[i];

			level = ((level << 4) + (intra_matrix[i] >> 1)) / intra_matrix[i];
			level = ((level + quantd) * mult) >> 17;
			coeff[i] = -(int16_t) level;
		} else if (data[i] > 0) {
			uint32_t level = data[i];

			level = ((level << 4) + (intra_matrix[i] >> 1)) / intra_matrix[i];
			level = ((level + quantd) * mult) >> 17;
			coeff[i] = (int16_t)level;
		} else {
			coeff[i] = 0;
		}
	}
}



/*    dequantize intra-block & clamp to [-2048,2047]	*/
    /* data[i] = (coeff[i] * default_intra_matrix[i] * quant2) >> 4; */


void
dequant4_intra_c(int16_t * data,
				 const int16_t * coeff,
				 const uint32_t quant,
				 const uint32_t dcscalar)
{
	uint32_t i;
	int16_t *intra_matrix;

	intra_matrix = get_intra_matrix();

	data[0] = (int16_t)(coeff[0] * dcscalar);
	if (data[0] < -2048) {
		data[0] = -2048;
	} else if (data[0] > 2047) {
		data[0] = 2047;
	}

	for (i = 1; i < 64; i++) {
		if (coeff[i] == 0) {
			data[i] = 0;
		} else if (coeff[i] < 0) {
			uint32_t level = -coeff[i];

			level = (level * intra_matrix[i] * quant) >> 3;
			data[i] = (level <= 2048 ? -(int16_t) level : -2048);
		} else					/* if (coeff[i] > 0) */
		{
			uint32_t level = coeff[i];

			level = (level * intra_matrix[i] * quant) >> 3;
			data[i] = (int16_t)(level <= 2047 ? level : 2047);
		}
	}
}



#if	0
/*    quantize inter-block	*/

    // level = DIV_DIV(16 * data[i], default_intra_matrix[i]);
    // coeff[i] = (level + quantd) / quant2;
    // sum += abs(level);
#endif

uint32_t
quant4_inter_c(int16_t * coeff,
			   const int16_t * data,
			   const uint32_t quant)
{
	const uint32_t mult = multipliers[quant];
	uint32_t sum = 0;
	uint32_t i;
	int16_t *inter_matrix;

	inter_matrix = get_inter_matrix();

	for (i = 0; i < 64; i++) {
		if (data[i] < 0) {
			uint32_t level = -data[i];

			level = ((level << 4) + (inter_matrix[i] >> 1)) / inter_matrix[i];
			level = (level * mult) >> 17;
			sum += level;
			coeff[i] = -(int16_t) level;
		} else if (data[i] > 0) {
			uint32_t level = data[i];

			level = ((level << 4) + (inter_matrix[i] >> 1)) / inter_matrix[i];
			level = (level * mult) >> 17;
			sum += level;
			coeff[i] = (int16_t)level;
		} else {
			coeff[i] = 0;
		}
	}
	return sum;
}



/* dequantize inter-block & clamp to [-2048,2047]
  data = ((2 * coeff + SIGN(coeff)) * inter_matrix[i] * quant) / 16
*/

void
dequant4_inter_c(int16_t * data,
				 const int16_t * coeff,
				 const uint32_t quant)
{
	uint32_t sum = 0;
	uint32_t i;
	int16_t *inter_matrix;

	inter_matrix = get_inter_matrix();

	for (i = 0; i < 64; i++) {
		if (coeff[i] == 0) {
			data[i] = 0;
		} else if (coeff[i] < 0) {
			int32_t level = -coeff[i];

			level = ((2 * level + 1) * inter_matrix[i] * quant) >> 4;
			data[i] = (level <= 2048 ? -level : -2048);
		} else					/* if (coeff[i] > 0) */
		{
			uint32_t level = coeff[i];

			level = ((2 * level + 1) * inter_matrix[i] * quant) >> 4;
			data[i] = (int16_t)(level <= 2047 ? level : 2047);
		}

		sum ^= data[i];
	}

	/* mismatch control */

	if ((sum & 1) == 0) {
		data[63] ^= 1;
	}
}