quant.cpp

《Visual C++小波变换技术与工程实践》靳济芳编著的光盘程序。

/* $Id: quant.c,v 1.15 1998/05/14 21:41:40 hjlee Exp $ */
/****************************************************************************/
/*   MPEG4 Visual Texture Coding (VTC) Mode Software                        */
/*                                                                          */
/*   This software was jointly developed by the following participants:     */
/*                                                                          */
/*   Single-quant,  multi-quant and flow control                            */
/*   are provided by  Sarnoff Corporation                                   */
/*     Iraj Sodagar   ([e-mail])                                    */
/*     Hung-Ju Lee    ([e-mail])                                   */
/*     Paul Hatrack   ([e-mail])                                 */
/*     Shipeng Li     ([e-mail])                                 */
/*     Bing-Bing Chai ([e-mail])                                   */
/*     B.S. Srinivas  ([e-mail])                               */
/*                                                                          */
/*   Bi-level is provided by Texas Instruments                              */
/*     Jie Liang      ([e-mail])                                        */
/*                                                                          */
/*   Shape Coding is provided by  OKI Electric Industry Co., Ltd.           */
/*     Zhixiong Wu    ([e-mail])                                 */
/*     Yoshihiro Ueda ([e-mail])                               */
/*     Toshifumi Kanamaru ([e-mail])                        */
/*                                                                          */
/*   OKI, Sharp, Sarnoff, TI and Microsoft contributed to bitstream         */
/*   exchange and bug fixing.                                               */
/*                                                                          */
/*                                                                          */
/* In the course of development of the MPEG-4 standard, this software       */
/* module is an implementation of a part of one or more MPEG-4 tools as     */
/* specified by the MPEG-4 standard.                                        */
/*                                                                          */
/* The copyright of this software belongs to ISO/IEC. ISO/IEC gives use     */
/* of the MPEG-4 standard free license to use this  software module or      */
/* modifications thereof for hardware or software products claiming         */
/* conformance to the MPEG-4 standard.                                      */
/*                                                                          */
/* Those intending to use this software module in hardware or software      */
/* products are advised that use may infringe existing  patents. The        */
/* original developers of this software module and their companies, the     */
/* subsequent editors and their companies, and ISO/IEC have no liability    */
/* and ISO/IEC have no liability for use of this software module or         */
/* modification thereof in an implementation.                               */
/*                                                                          */
/* Permission is granted to MPEG members to use, copy, modify,              */
/* and distribute the software modules ( or portions thereof )              */
/* for standardization activity within ISO/IEC JTC1/SC29/WG11.              */
/*                                                                          */
/* Copyright 1995, 1996, 1997, 1998 ISO/IEC                                 */
/****************************************************************************/

/************************************************************/
/*     Sarnoff Very Low Bit Rate Still Image Coder          */
/*     Copyright 1995, 1996, 1997, 1998 Sarnoff Corporation */
/************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include "basic.hpp"
#include "dataStruct.hpp"
#include "quant.hpp"


/* sign */
#define SGN(x) (((x)<0) ? -1 : 1)
/* Integer rounding */
#define IROUND(n,d) ( ((n)/(d)) + (((n)%(d) > (d-1)/2) || (n)<(d))) 
/* Integer ceiling */
#define ICEIL(n,d) ( ((n)/(d)) + ((n)%(d)!=0 || (n)<(d)) ) 

/* For partitionType bit field processing */
#define MASK_fromReduced  ((UChar)'\1')
#define MASK_fromDeadZone ((UChar)'\2')

#define SET_fromReduced(x)  ((x) |= MASK_fromReduced)
#define SET_fromDeadZone(x) ((x) |= MASK_fromDeadZone)

#define CLR_fromReduced(x)  ((x) &= ~(MASK_fromReduced))
#define CLR_fromDeadZone(x) ((x) &= ~(MASK_fromDeadZone))

#define fromReduced(x)  ((x) & MASK_fromReduced)
#define fromDeadZone(x) (((x) & MASK_fromDeadZone)>>1)


/*------------------------- QUANTIZATION --------------------------*/


/* 
函数输入：
quantState *state：		指向表征量化器状态的指针；
Int *statePrevQ：		指向先前量化状态的指针；
Int initialValue：		进行量化的系数值。
函数功能描述：
对一个给定的系数值完成其量化器的初始化工作。
函数功能评价：
本函数必须在量化前调用。此外，对于每一次进行量化的系数，必须有一个独立的量化器状态结构来进行记录，这样可以保证系数的并行量化处理。每一个需要进行量化的系数，只需要调用一次量化器初始化即可。

*/

Void CVTCCommon::initQuantSingleStage(quantState *state, Int *statePrevQ, Int initialVal)
{
  state->residualValue = initialVal;
  state->partitionType = 0x2; /* fromReduced = 0 and fromDeadZone  = 1 */
  *statePrevQ          = 0;
}

/*
函数输入：
Int Q：			量化数值，它表示预设的量化级别的多少；
quantState *state：	量化器状态值；
Int *statePrevQ：	前线量化的数值状态；
Int updatePrevQ：	是否更新statePrevQ的数值：0表示不更新；非0表示需要进行更新。
函数返回值：
Qindex，即新的量化索引（量化级别索引）。
函数功能描述：
实现系数的量化。
函数功能评价：
调用initQuantSingleStage函数对量化器完成初始化后，该函数将在当前量化值得基础上计算出一个新的量化索引。

  */

Int CVTCEncoder::quantSingleStage(Int Q, quantState *state, Int *statePrevQ,
				 Int updatePrevQ)
{
	Int refLevs;	//在新的量化级上有多少细化级别
	Int QIndex;	//完成本级量化后返回的新的量化索引
//完成量化器的初始化工作后第一次调用量化函数
	if (*statePrevQ==0)
	{
		QIndex = state->residualValue/Q;

		//更新量化器状态
		if (QIndex)
			state->residualValue = abs(state->residualValue) - (abs(QIndex)*Q);
		CLR_fromReduced(state->partitionType);
		if (QIndex)
			CLR_fromDeadZone(state->partitionType);
		else
			SET_fromDeadZone(state->partitionType);
 
		if (updatePrevQ)
 			*statePrevQ = Q;

		return QIndex;
	}

//非第一次调用量化函数
	//由上一次量化状态值得到此次量化的细化级别数
	refLevs = IROUND(*statePrevQ,Q);
	//如果细化没有完成，继续！并且不改变量化器的状态信息
	if (refLevs<=1)
		QIndex = 0;
	else
	{
		Int inDeadZone;			//是否在量化静区（dead zone）
		Int lastQUsed;			//最后一次量化所用的Q值
		Int val;				//用于量化的系数值
		Int lastLevSize;			//上一次量化的量化级别数
		Int newQUsed, newStateQ;
		Int excess;

		//初始化上一次实用的量化系数值
		lastQUsed = *statePrevQ;
		
		//更新得到一个新的Q值状态
		newStateQ = newQUsed = ICEIL(lastQUsed,refLevs);
		if (updatePrevQ)
			*statePrevQ = newStateQ;

		//获取最后的量化级别步长
		lastLevSize = lastQUsed-fromReduced(state->partitionType);

		//查看细化细节是否有效
		if (refLevs*(newQUsed-1) >= lastLevSize)
		{
			--newQUsed;
			excess=0;
		}
		else
			excess=lastLevSize-refLevs*newQUsed;

		//设置量化静区的指示
		inDeadZone = fromDeadZone(state->partitionType);
		
		//设置上一量化后的区间左端数值
		val=state->residualValue;

		//计算QIndex，并更新residualValue和fromReduced的状态
		if (excess==0)
		{
			QIndex = val/newQUsed;
			if (newQUsed < newStateQ)
	SET_fromReduced(state->partitionType);
			else
	CLR_fromReduced(state->partitionType);

			
			if (QIndex)
	state->residualValue -= QIndex*newQUsed;
		}
		else
		{
			Int reducedParStart; 
			Int reducedIdx;

			reducedParStart = newQUsed*(refLevs+excess);
			if (abs(val) >= reducedParStart)
			{
	SET_fromReduced(state->partitionType);
	QIndex = SGN(state->residualValue)*(refLevs+excess);
	state->residualValue -= QIndex*newQUsed;

	--newQUsed;
	reducedIdx = 
		SGN(state->residualValue) * (abs(val)-reducedParStart) / newQUsed;
	QIndex += reducedIdx;
	state->residualValue -= reducedIdx*newQUsed;
			}
			else
			{
	CLR_fromReduced(state->partitionType);
	QIndex = val/newQUsed;
	state->residualValue -= QIndex*newQUsed;
			}
		}
		
		if (inDeadZone && QIndex)
		{
			//系数的符号信息，那么可以保证量化差异值为正数
			state->residualValue = abs(state->residualValue);
			CLR_fromDeadZone(state->partitionType);
		}
	}

	//返回新的量化索引
	return QIndex;