mbprediction.c

这是一个压缩解压包,用C语言进行编程的,里面有详细的源代码.

/*****************************************************************************
 *
 *  XVID MPEG-4 VIDEO CODEC
 *  - Prediction module -
 *
 *  Copyright (C) 2001-2003 Michael Militzer <[e-mail]>
 *                2001-2003 Peter Ross <[e-mail]>
 *
 *  This program 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
 *
 * $Id: mbprediction.c,v 1.18 2005/11/22 10:23:01 suxen_drol Exp $
 *
 ****************************************************************************/

#include <stdlib.h>

#include "../global.h"
#include "../encoder.h"
#include "mbprediction.h"
#include "../utils/mbfunctions.h"
#include "../bitstream/cbp.h"
#include "../bitstream/mbcoding.h"
#include "../bitstream/zigzag.h"


static int __inline
rescale(int predict_quant,
		int current_quant,
		int coeff)
{
	return (coeff != 0) ? DIV_DIV((coeff) * (predict_quant),
								  (current_quant)) : 0;
}


static const int16_t default_acdc_values[15] = {
	1024,
	0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0
};


/*	get dc/ac prediction direction for a single block and place
	predictor values into MB->pred_values[j][..]
*/


void
predict_acdc(MACROBLOCK * pMBs,
			 uint32_t x,
			 uint32_t y,
			 uint32_t mb_width,
			 uint32_t block,
			 int16_t qcoeff[64],
			 uint32_t current_quant,
			 int32_t iDcScaler,
			 int16_t predictors[8],
			 const int bound)

{
	const int mbpos = (y * mb_width) + x;
	int16_t *left, *top, *diag, *current;

	int32_t left_quant = current_quant;
	int32_t top_quant = current_quant;

	const int16_t *pLeft = default_acdc_values;
	const int16_t *pTop = default_acdc_values;
	const int16_t *pDiag = default_acdc_values;

	uint32_t index = x + y * mb_width;	/* current macroblock */
	int *acpred_direction = &pMBs[index].acpred_directions[block];
	uint32_t i;

	left = top = diag = current = NULL;

	/* grab left,top and diag macroblocks */

	/* left macroblock */

	if (x && mbpos >= bound + 1  &&
		(pMBs[index - 1].mode == MODE_INTRA ||
		 pMBs[index - 1].mode == MODE_INTRA_Q)) {

		left = (int16_t*)pMBs[index - 1].pred_values[0];
		left_quant = pMBs[index - 1].quant;
	}
	/* top macroblock */

	if (mbpos >= bound + (int)mb_width &&
		(pMBs[index - mb_width].mode == MODE_INTRA ||
		 pMBs[index - mb_width].mode == MODE_INTRA_Q)) {

		top = (int16_t*)pMBs[index - mb_width].pred_values[0];
		top_quant = pMBs[index - mb_width].quant;
	}
	/* diag macroblock */

	if (x && mbpos >= bound + (int)mb_width + 1 &&
		(pMBs[index - 1 - mb_width].mode == MODE_INTRA ||
		 pMBs[index - 1 - mb_width].mode == MODE_INTRA_Q)) {

		diag = (int16_t*)pMBs[index - 1 - mb_width].pred_values[0];
	}

	current = (int16_t*)pMBs[index].pred_values[0];

	/* now grab pLeft, pTop, pDiag _blocks_ */

	switch (block) {

	case 0:
		if (left)
			pLeft = left + MBPRED_SIZE;

		if (top)
			pTop = top + (MBPRED_SIZE << 1);

		if (diag)
			pDiag = diag + 3 * MBPRED_SIZE;

		break;

	case 1:
		pLeft = current;
		left_quant = current_quant;

		if (top) {
			pTop = top + 3 * MBPRED_SIZE;
			pDiag = top + (MBPRED_SIZE << 1);
		}
		break;

	case 2:
		if (left) {
			pLeft = left + 3 * MBPRED_SIZE;
			pDiag = left + MBPRED_SIZE;
		}

		pTop = current;
		top_quant = current_quant;

		break;

	case 3:
		pLeft = current + (MBPRED_SIZE << 1);
		left_quant = current_quant;

		pTop = current + MBPRED_SIZE;
		top_quant = current_quant;

		pDiag = current;

		break;

	case 4:
		if (left)
			pLeft = left + (MBPRED_SIZE << 2);
		if (top)
			pTop = top + (MBPRED_SIZE << 2);
		if (diag)
			pDiag = diag + (MBPRED_SIZE << 2);
		break;

	case 5:
		if (left)
			pLeft = left + 5 * MBPRED_SIZE;
		if (top)
			pTop = top + 5 * MBPRED_SIZE;
		if (diag)
			pDiag = diag + 5 * MBPRED_SIZE;
		break;
	}

	/* determine ac prediction direction & ac/dc predictor place rescaled ac/dc
	 * predictions into predictors[] for later use */
	if (abs(pLeft[0] - pDiag[0]) < abs(pDiag[0] - pTop[0])) {
		*acpred_direction = 1;	/* vertical */
		predictors[0] = DIV_DIV(pTop[0], iDcScaler);
		for (i = 1; i < 8; i++) {
			predictors[i] = rescale(top_quant, current_quant, pTop[i]);
		}
	} else {
		*acpred_direction = 2;	/* horizontal */
		predictors[0] = DIV_DIV(pLeft[0], iDcScaler);
		for (i = 1; i < 8; i++) {
			predictors[i] = rescale(left_quant, current_quant, pLeft[i + 7]);
		}
	}
}


/* decoder: add predictors to dct_codes[] and
   store current coeffs to pred_values[] for future prediction
*/

/* Up to this version, no DC clipping was performed, so we try to be backward
 * compatible to avoid artifacts */
#define BS_VERSION_BUGGY_DC_CLIPPING 34

void
add_acdc(MACROBLOCK * pMB,
		 uint32_t block,
		 int16_t dct_codes[64],
		 uint32_t iDcScaler,
		 int16_t predictors[8],
		 const int bsversion)
{
	uint8_t acpred_direction = pMB->acpred_directions[block];
	int16_t *pCurrent = (int16_t*)pMB->pred_values[block];
	uint32_t i;

	DPRINTF(XVID_DEBUG_COEFF,"predictor[0] %i\n", predictors[0]);

	dct_codes[0] += predictors[0];	/* dc prediction */
	pCurrent[0] = dct_codes[0]*iDcScaler;
	if (!bsversion || bsversion > BS_VERSION_BUGGY_DC_CLIPPING) {
		pCurrent[0] = CLIP(pCurrent[0], -2048, 2047);
	}

	if (acpred_direction == 1) {
		for (i = 1; i < 8; i++) {
			int level = dct_codes[i] + predictors[i];

			DPRINTF(XVID_DEBUG_COEFF,"predictor[%i] %i\n",i, predictors[i]);

			dct_codes[i] = level;
			pCurrent[i] = level;
			pCurrent[i + 7] = dct_codes[i * 8];
		}
	} else if (acpred_direction == 2) {
		for (i = 1; i < 8; i++) {
			int level = dct_codes[i * 8] + predictors[i];
			DPRINTF(XVID_DEBUG_COEFF,"predictor[%i] %i\n",i*8, predictors[i]);

			dct_codes[i * 8] = level;
			pCurrent[i + 7] = level;
			pCurrent[i] = dct_codes[i];
		}
	} else {
		for (i = 1; i < 8; i++) {
			pCurrent[i] = dct_codes[i];
			pCurrent[i + 7] = dct_codes[i * 8];
		}
	}
}



/*****************************************************************************
 ****************************************************************************/

/* encoder: subtract predictors from qcoeff[] and calculate S1/S2

returns sum of coeefficients *saved* if prediction is enabled

S1 = sum of all (qcoeff - prediction)
S2 = sum of all qcoeff
*/

static int
calc_acdc_coeff(MACROBLOCK * pMB,
		  uint32_t block,
		  int16_t qcoeff[64],
		  uint32_t iDcScaler,
		  int16_t predictors[8])
{
	int16_t *pCurrent = (int16_t*)pMB->pred_values[block];
	uint32_t i;
	int S1 = 0, S2 = 0;


	/* store current coeffs to pred_values[] for future prediction */

	pCurrent[0] = qcoeff[0] * iDcScaler;
	pCurrent[0] = CLIP(pCurrent[0], -2048, 2047);
	for (i = 1; i < 8; i++) {
		pCurrent[i] = qcoeff[i];
		pCurrent[i + 7] = qcoeff[i * 8];
	}

	/* subtract predictors and store back in predictors[] */

	qcoeff[0] = qcoeff[0] - predictors[0];

	if (pMB->acpred_directions[block] == 1) {
		for (i = 1; i < 8; i++) {
			int16_t level;

			level = qcoeff[i];
			S2 += abs(level);
			level -= predictors[i];
			S1 += abs(level);
			predictors[i] = level;
		}
	} else						/* acpred_direction == 2 */
	{
		for (i = 1; i < 8; i++) {
			int16_t level;

			level = qcoeff[i * 8];
			S2 += abs(level);
			level -= predictors[i];
			S1 += abs(level);
			predictors[i] = level;
		}

	}


	return S2 - S1;
}



/* returns the bits *saved* if prediction is enabled */

static int
calc_acdc_bits(MACROBLOCK * pMB,
		  uint32_t block,
		  int16_t qcoeff[64],
		  uint32_t iDcScaler,
		  int16_t predictors[8])
{
	const int direction = pMB->acpred_directions[block];
	int16_t *pCurrent = (int16_t*)pMB->pred_values[block];
	int16_t tmp[8];
	unsigned int i;