noiseless.c

nds上大名鼎鼎的DSOrganize 2.8最新源代码。很值得研究。

/* ***** BEGIN LICENSE BLOCK *****  
 * Source last modified: $Id: noiseless.c,v 1.1.2.1 2005/02/26 02:05:12 jrecker Exp $ 
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 * Portions Copyright (c) 1995-2005 RealNetworks, Inc. All Rights Reserved.  
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 * to this file, the RCSL.  Please see the applicable RPSL or RCSL for 
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 * This file is part of the Helix DNA Technology. RealNetworks is the 
 * developer of the Original Code and owns the copyrights in the 
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 * ***** END LICENSE BLOCK ***** */  

/**************************************************************************************
 * Fixed-point HE-AAC decoder
 * Jon Recker ([e-mail])
 * February 2005
 *
 * noiseless.c - decode channel info, scalefactors, quantized coefficients, 
 *                 scalefactor band codebook, and TNS coefficients from bitstream
 **************************************************************************************/

#include "coder.h"

/**************************************************************************************
 * Function:    DecodeICSInfo
 *
 * Description: decode individual channel stream info
 *
 * Inputs:      BitStreamInfo struct pointing to start of ICS info
 *                (14496-3, table 4.4.6) 
 *              sample rate index
 *
 * Outputs:     updated icsInfo struct
 *
 * Return:      none
 **************************************************************************************/
void DecodeICSInfo(BitStreamInfo *bsi, ICSInfo *icsInfo, int sampRateIdx)
{
	int sfb, g, mask;

	icsInfo->icsResBit =      GetBits(bsi, 1);
	icsInfo->winSequence =    GetBits(bsi, 2);
	icsInfo->winShape =       GetBits(bsi, 1);
	if (icsInfo->winSequence == 2) {
		/* short block */
		icsInfo->maxSFB =     GetBits(bsi, 4);
		icsInfo->sfGroup =    GetBits(bsi, 7);
		icsInfo->numWinGroup =    1;
		icsInfo->winGroupLen[0] = 1;
		mask = 0x40;	/* start with bit 6 */
		for (g = 0; g < 7; g++) {
			if (icsInfo->sfGroup & mask)	{ 
				icsInfo->winGroupLen[icsInfo->numWinGroup - 1]++;
			} else { 
				icsInfo->numWinGroup++; 
				icsInfo->winGroupLen[icsInfo->numWinGroup - 1] = 1; 
			}
			mask >>= 1;
		}
	} else {
		/* long block */
		icsInfo->maxSFB =               GetBits(bsi, 6);
		icsInfo->predictorDataPresent = GetBits(bsi, 1);
		if (icsInfo->predictorDataPresent) {
			icsInfo->predictorReset =   GetBits(bsi, 1);
			if (icsInfo->predictorReset)
				icsInfo->predictorResetGroupNum = GetBits(bsi, 5);
			for (sfb = 0; sfb < MIN(icsInfo->maxSFB, predSFBMax[sampRateIdx]); sfb++)
				icsInfo->predictionUsed[sfb] = GetBits(bsi, 1);
		}
		icsInfo->numWinGroup = 1;
		icsInfo->winGroupLen[0] = 1;
	}
}

/**************************************************************************************
 * Function:    DecodeSectionData
 *
 * Description: decode section data (scale factor band groupings and 
 *                associated Huffman codebooks)
 *
 * Inputs:      BitStreamInfo struct pointing to start of ICS info
 *                (14496-3, table 4.4.25)
 *              window sequence (short or long blocks)
 *              number of window groups (1 for long blocks, 1-8 for short blocks)
 *              max coded scalefactor band
 *
 * Outputs:     index of Huffman codebook for each scalefactor band in each section
 *
 * Return:      none
 *
 * Notes:       sectCB, sectEnd, sfbCodeBook, ordered by window groups for short blocks
 **************************************************************************************/
static void DecodeSectionData(BitStreamInfo *bsi, int winSequence, int numWinGrp, int maxSFB, unsigned char *sfbCodeBook)
{
	int g, cb, sfb;
	int sectLen, sectLenBits, sectLenIncr, sectEscapeVal;

	sectLenBits = (winSequence == 2 ? 3 : 5);
	sectEscapeVal = (1 << sectLenBits) - 1;

	for (g = 0; g < numWinGrp; g++) {
		sfb = 0;
		while (sfb < maxSFB) {
			cb = GetBits(bsi, 4);	/* next section codebook */
			sectLen = 0;
			do {
				sectLenIncr = GetBits(bsi, sectLenBits);
				sectLen += sectLenIncr;
			} while (sectLenIncr == sectEscapeVal);

			sfb += sectLen;
			while (sectLen--)
				*sfbCodeBook++ = (unsigned char)cb;
		}
		ASSERT(sfb == maxSFB);
	}
}

/**************************************************************************************
 * Function:    DecodeOneScaleFactor
 *
 * Description: decode one scalefactor using scalefactor Huffman codebook
 *
 * Inputs:      BitStreamInfo struct pointing to start of next coded scalefactor
 *
 * Outputs:     updated BitstreamInfo struct
 *
 * Return:      one decoded scalefactor, including index_offset of -60
 **************************************************************************************/
static int DecodeOneScaleFactor(BitStreamInfo *bsi)
{
	int nBits, val;
	unsigned int bitBuf;

	/* decode next scalefactor from bitstream */
	bitBuf = GetBitsNoAdvance(bsi, huffTabScaleFactInfo.maxBits) << (32 - huffTabScaleFactInfo.maxBits);
	nBits = DecodeHuffmanScalar(huffTabScaleFact, &huffTabScaleFactInfo, bitBuf, &val);
	AdvanceBitstream(bsi, nBits);

	return val;
}

/**************************************************************************************
 * Function:    DecodeScaleFactors
 *
 * Description: decode scalefactors, PNS energy, and intensity stereo weights
 *
 * Inputs:      BitStreamInfo struct pointing to start of ICS info
 *                (14496-3, table 4.4.26)
 *              number of window groups (1 for long blocks, 1-8 for short blocks)
 *              max coded scalefactor band
 *              global gain (starting value for differential scalefactor coding)
 *              index of Huffman codebook for each scalefactor band in each section
 *
 * Outputs:     decoded scalefactor for each section
 *
 * Return:      none
 *
 * Notes:       sfbCodeBook, scaleFactors ordered by window groups for short blocks
 *              for section with codebook 13, scaleFactors buffer has decoded PNS
 *                energy instead of regular scalefactor
 *              for section with codebook 14 or 15, scaleFactors buffer has intensity
 *                stereo weight instead of regular scalefactor
 **************************************************************************************/
static void DecodeScaleFactors(BitStreamInfo *bsi, int numWinGrp, int maxSFB, int globalGain,
								  unsigned char *sfbCodeBook, short *scaleFactors)
{
	int g, sfbCB, nrg, npf, val, sf, is;

	/* starting values for differential coding */
	sf = globalGain;
	is = 0;
	nrg = globalGain - 90 - 256;
	npf = 1;

	for (g = 0; g < numWinGrp * maxSFB; g++) {
		sfbCB = *sfbCodeBook++;

		if (sfbCB  == 14 || sfbCB == 15) {
			/* intensity stereo - differential coding */
			val = DecodeOneScaleFactor(bsi);
			is += val;
			*scaleFactors++ = (short)is;
		} else if (sfbCB == 13) {
			/* PNS - first energy is directly coded, rest are Huffman coded (npf = noise_pcm_flag) */ 
			if (npf) {
				val = GetBits(bsi, 9);
				npf = 0;
			} else {
				val = DecodeOneScaleFactor(bsi);
			}
			nrg += val;
			*scaleFactors++ = (short)nrg;
		} else if (sfbCB >= 1 && sfbCB <= 11) {
			/* regular (non-zero) region - differential coding */
			val = DecodeOneScaleFactor(bsi);
			sf += val;
			*scaleFactors++ = (short)sf;
		} else {
			/* inactive scalefactor band if codebook 0 */
			*scaleFactors++ = 0;
		}
	}
}

/**************************************************************************************
 * Function:    DecodePulseInfo
 *
 * Description: decode pulse information
 *
 * Inputs:      BitStreamInfo struct pointing to start of pulse info
 *                (14496-3, table 4.4.7)
 *