adapt_quant.c

mpeg4代码,比较具体

/*****************************************************************************
 *
 *  XVID MPEG-4 VIDEO CODEC
 *  - Adaptive quantization functions -
 *
 *  Copyright(C) 2002 Peter Ross <[e-mail]>
 *               2002 Christoph Lampert <[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: adapt_quant.c,v 1.13 2002/11/26 23:44:11 edgomez Exp $
 *
 ****************************************************************************/

#include "../portab.h"
#include "adapt_quant.h"

#include <stdlib.h>				/* free, malloc */

#define MAX(a,b)      (((a) > (b)) ? (a) : (b))
#define RDIFF(a,b)    ((int)(a+0.5)-(int)(b+0.5))

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

int
normalize_quantizer_field(float *in,
						  int *out,
						  int num,
						  int min_quant,
						  int max_quant)
{
	int i;
	int finished;

	do {
		finished = 1;
		for (i = 1; i < num; i++) {
			if (RDIFF(in[i], in[i - 1]) > 2) {
				in[i] -= (float) 0.5;
				finished = 0;
			} else if (RDIFF(in[i], in[i - 1]) < -2) {
				in[i - 1] -= (float) 0.5;
				finished = 0;
			}

			if (in[i] > max_quant) {
				in[i] = (float) max_quant;
				finished = 0;
			}
			if (in[i] < min_quant) {
				in[i] = (float) min_quant;
				finished = 0;
			}
			if (in[i - 1] > max_quant) {
				in[i - 1] = (float) max_quant;
				finished = 0;
			}
			if (in[i - 1] < min_quant) {
				in[i - 1] = (float) min_quant;
				finished = 0;
			}
		}
	} while (!finished);

	out[0] = 0;
	for (i = 1; i < num; i++)
		out[i] = RDIFF(in[i], in[i - 1]);

	return (int) (in[0] + 0.5);
}

int
adaptive_quantization(unsigned char *buf,
					  int stride,
					  int *intquant,
					  int framequant,
					  int min_quant,
					  int max_quant,
					  int mb_width,
					  int mb_height)	/* no qstride because normalization */
{
	int i, j, k, l;

	float *quant;
	unsigned char *ptr;
	float *val;
	float global = 0.;
	uint32_t mid_range = 0;

	const float DarkAmpl = 14 / 2;
	const float BrightAmpl = 10 / 2;
	const float DarkThres = 70;
	const float BrightThres = 200;

	const float GlobalDarkThres = 60;
	const float GlobalBrightThres = 170;

	const float MidRangeThres = 20;
	const float UpperLimit = 200;
	const float LowerLimit = 25;


	if (!(quant = (float *) malloc(mb_width * mb_height * sizeof(float))))
		return(-1);

	if(!(val = (float *) malloc(mb_width * mb_height * sizeof(float)))) {
		free(quant);
		return(-1);
	}

	for (k = 0; k < mb_height; k++) {
		for (l = 0; l < mb_width; l++)	/* do this for all macroblocks individually  */
		{
			quant[k * mb_width + l] = (float) framequant;

			/* calculate luminance-masking */
			ptr = &buf[16 * k * stride + 16 * l];	/* address of MB */

			val[k * mb_width + l] = 0.;

			for (i = 0; i < 16; i++)
				for (j = 0; j < 16; j++)
					val[k * mb_width + l] += ptr[i * stride + j];
			val[k * mb_width + l] /= 256.;
			global +=val[k * mb_width + l];

			if ((val[k * mb_width + l] > LowerLimit) &&
				(val[k * mb_width + l] < UpperLimit))
				mid_range++;
		}
	}

	global /=mb_width * mb_height;

	if (((global <GlobalBrightThres) &&(global >GlobalDarkThres))
		|| (mid_range < MidRangeThres)) {
		for (k = 0; k < mb_height; k++) {
			for (l = 0; l < mb_width; l++)	/* do this for all macroblocks individually  */
			{
				if (val[k * mb_width + l] < DarkThres)
					quant[k * mb_width + l] +=
						DarkAmpl * (DarkThres -
									val[k * mb_width + l]) / DarkThres;
				else if (val[k * mb_width + l] > BrightThres)
					quant[k * mb_width + l] +=
						BrightAmpl * (val[k * mb_width + l] -
									  BrightThres) / (255 - BrightThres);
			}
		}
	}

	i = normalize_quantizer_field(quant, intquant,
								  mb_width * mb_height,
								  min_quant, max_quant);

	free(val);
	free(quant);

	return(i);

}