sbrside.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: sbrside.c,v 1.1.2.2 2005/05/24 20:34:40 albertofloyd Exp $ 
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/**************************************************************************************
 * Fixed-point HE-AAC decoder
 * Jon Recker ([e-mail])
 * February 2005
 *
 * sbrside.c - functions for unpacking side info from SBR bitstream
 **************************************************************************************/

#include "sbr.h"

/**************************************************************************************
 * Function:    GetSampRateIdx
 *
 * Description: get index of given sample rate
 *
 * Inputs:      sample rate (in Hz)
 *
 * Outputs:     none
 *
 * Return:      index of sample rate (table 1.15 in 14496-3:2001(E))
 *              -1 if sample rate not found in table
 **************************************************************************************/
int GetSampRateIdx(int sampRate)
{
	int idx;

	for (idx = 0; idx < NUM_SAMPLE_RATES; idx++) {
		if (sampRate == sampRateTab[idx])
			return idx;
	}

	return -1;
}

/**************************************************************************************
 * Function:    UnpackSBRHeader
 *
 * Description: unpack SBR header (table 4.56)
 *
 * Inputs:      BitStreamInfo struct pointing to start of SBR header
 *
 * Outputs:     initialized SBRHeader struct for this SCE/CPE block
 *
 * Return:      non-zero if frame reset is triggered, zero otherwise
 **************************************************************************************/
int UnpackSBRHeader(BitStreamInfo *bsi, SBRHeader *sbrHdr)
{
	SBRHeader sbrHdrPrev;

	/* save previous values so we know whether to reset decoder */
	sbrHdrPrev.startFreq =     sbrHdr->startFreq;
	sbrHdrPrev.stopFreq =      sbrHdr->stopFreq;
	sbrHdrPrev.freqScale =     sbrHdr->freqScale;
	sbrHdrPrev.alterScale =    sbrHdr->alterScale;
	sbrHdrPrev.crossOverBand = sbrHdr->crossOverBand;
	sbrHdrPrev.noiseBands =    sbrHdr->noiseBands;

	sbrHdr->ampRes =        GetBits(bsi, 1);
	sbrHdr->startFreq =     GetBits(bsi, 4);
	sbrHdr->stopFreq =      GetBits(bsi, 4);
	sbrHdr->crossOverBand = GetBits(bsi, 3);
	sbrHdr->resBitsHdr =    GetBits(bsi, 2);
	sbrHdr->hdrExtra1 =     GetBits(bsi, 1);
	sbrHdr->hdrExtra2 =     GetBits(bsi, 1);

	if (sbrHdr->hdrExtra1) {
		sbrHdr->freqScale =    GetBits(bsi, 2);
		sbrHdr->alterScale =   GetBits(bsi, 1);
		sbrHdr->noiseBands =   GetBits(bsi, 2);
	} else {
		/* defaults */
		sbrHdr->freqScale =    2;
		sbrHdr->alterScale =   1;
		sbrHdr->noiseBands =   2;
	}

	if (sbrHdr->hdrExtra2) {
		sbrHdr->limiterBands = GetBits(bsi, 2);
		sbrHdr->limiterGains = GetBits(bsi, 2);
		sbrHdr->interpFreq =   GetBits(bsi, 1);
		sbrHdr->smoothMode =   GetBits(bsi, 1);
	} else {
		/* defaults */
		sbrHdr->limiterBands = 2;
		sbrHdr->limiterGains = 2;
		sbrHdr->interpFreq =   1;
		sbrHdr->smoothMode =   1;
	}
	sbrHdr->count++;

	/* if any of these have changed from previous frame, reset the SBR module */
	if (sbrHdr->startFreq != sbrHdrPrev.startFreq || sbrHdr->stopFreq != sbrHdrPrev.stopFreq ||
		sbrHdr->freqScale != sbrHdrPrev.freqScale || sbrHdr->alterScale != sbrHdrPrev.alterScale ||
		sbrHdr->crossOverBand != sbrHdrPrev.crossOverBand || sbrHdr->noiseBands != sbrHdrPrev.noiseBands
		)
		return -1;
	else
		return 0;
}

/* cLog2[i] = ceil(log2(i)) (disregard i == 0) */
static const unsigned char cLog2[9] = {0, 0, 1, 2, 2, 3, 3, 3, 3};

/**************************************************************************************
 * Function:    UnpackSBRGrid
 *
 * Description: unpack SBR grid (table 4.62)
 *
 * Inputs:      BitStreamInfo struct pointing to start of SBR grid
 *              initialized SBRHeader struct for this SCE/CPE block
 * 
 * Outputs:     initialized SBRGrid struct for this channel
 *
 * Return:      none
 **************************************************************************************/
static void UnpackSBRGrid(BitStreamInfo *bsi, SBRHeader *sbrHdr, SBRGrid *sbrGrid)
{
	int numEnvRaw, env, rel, pBits, border, middleBorder=0;
	unsigned char relBordLead[MAX_NUM_ENV], relBordTrail[MAX_NUM_ENV];
	unsigned char relBorder0[3], relBorder1[3], relBorder[3];
	unsigned char numRelBorder0, numRelBorder1, numRelBorder, numRelLead=0, numRelTrail;
	unsigned char absBordLead=0, absBordTrail=0, absBorder;
	
	sbrGrid->ampResFrame = sbrHdr->ampRes;
	sbrGrid->frameClass = GetBits(bsi, 2);
	switch (sbrGrid->frameClass) {

	case SBR_GRID_FIXFIX:
		numEnvRaw = GetBits(bsi, 2);
		sbrGrid->numEnv = (1 << numEnvRaw);
		if (sbrGrid->numEnv == 1)
			sbrGrid->ampResFrame = 0;

		ASSERT(sbrGrid->numEnv == 1 || sbrGrid->numEnv == 2 || sbrGrid->numEnv == 4);

		sbrGrid->freqRes[0] = GetBits(bsi, 1);
		for (env = 1; env < sbrGrid->numEnv; env++)
			 sbrGrid->freqRes[env] = sbrGrid->freqRes[0];

		absBordLead =  0;
		absBordTrail = NUM_TIME_SLOTS;
		numRelLead =   sbrGrid->numEnv - 1;
		numRelTrail =  0;

		/* numEnv = 1, 2, or 4 */
		if (sbrGrid->numEnv == 1)		border = NUM_TIME_SLOTS / 1;
		else if (sbrGrid->numEnv == 2)	border = NUM_TIME_SLOTS / 2;
		else							border = NUM_TIME_SLOTS / 4;

		for (rel = 0; rel < numRelLead; rel++)
			relBordLead[rel] = border;

		middleBorder = (sbrGrid->numEnv >> 1);

		break;

	case SBR_GRID_FIXVAR:
		absBorder = GetBits(bsi, 2) + NUM_TIME_SLOTS;
		numRelBorder = GetBits(bsi, 2);
		sbrGrid->numEnv = numRelBorder + 1;
		for (rel = 0; rel < numRelBorder; rel++)
			relBorder[rel] = 2*GetBits(bsi, 2) + 2;

		pBits = cLog2[sbrGrid->numEnv + 1];
		sbrGrid->pointer = GetBits(bsi, pBits);

		for (env = sbrGrid->numEnv - 1; env >= 0; env--)
			sbrGrid->freqRes[env] = GetBits(bsi, 1);

		absBordLead =  0;
		absBordTrail = absBorder;
		numRelLead =   0;
		numRelTrail =  numRelBorder;

		for (rel = 0; rel < numRelTrail; rel++)
			relBordTrail[rel] = relBorder[rel];

		if (sbrGrid->pointer > 1)			middleBorder = sbrGrid->numEnv + 1 - sbrGrid->pointer;
		else								middleBorder = sbrGrid->numEnv - 1;

		break;

	case SBR_GRID_VARFIX:
		absBorder = GetBits(bsi, 2);
		numRelBorder = GetBits(bsi, 2);
		sbrGrid->numEnv = numRelBorder + 1;
		for (rel = 0; rel < numRelBorder; rel++)
			relBorder[rel] = 2*GetBits(bsi, 2) + 2;

		pBits = cLog2[sbrGrid->numEnv + 1];
		sbrGrid->pointer = GetBits(bsi, pBits);

		for (env = 0; env < sbrGrid->numEnv; env++)
			sbrGrid->freqRes[env] = GetBits(bsi, 1);

		absBordLead =  absBorder;
		absBordTrail = NUM_TIME_SLOTS;
		numRelLead =   numRelBorder;
		numRelTrail =  0;

		for (rel = 0; rel < numRelLead; rel++)
			relBordLead[rel] = relBorder[rel];

		if (sbrGrid->pointer == 0)			middleBorder = 1;
		else if (sbrGrid->pointer == 1)		middleBorder = sbrGrid->numEnv - 1;
		else								middleBorder = sbrGrid->pointer - 1;

		break;

	case SBR_GRID_VARVAR:
		absBordLead =   GetBits(bsi, 2);	/* absBorder0 */
		absBordTrail =  GetBits(bsi, 2) + NUM_TIME_SLOTS;	/* absBorder1 */
		numRelBorder0 = GetBits(bsi, 2);
		numRelBorder1 = GetBits(bsi, 2);

		sbrGrid->numEnv = numRelBorder0 + numRelBorder1 + 1;
		ASSERT(sbrGrid->numEnv <= 5);

		for (rel = 0; rel < numRelBorder0; rel++)
			relBorder0[rel] = 2*GetBits(bsi, 2) + 2;

		for (rel = 0; rel < numRelBorder1; rel++)
			relBorder1[rel] = 2*GetBits(bsi, 2) + 2;

		pBits = cLog2[numRelBorder0 + numRelBorder1 + 2];
		sbrGrid->pointer = GetBits(bsi, pBits);

		for (env = 0; env < sbrGrid->numEnv; env++)
			sbrGrid->freqRes[env] = GetBits(bsi, 1);

		numRelLead =  numRelBorder0;
		numRelTrail = numRelBorder1;

		for (rel = 0; rel < numRelLead; rel++)
			relBordLead[rel] = relBorder0[rel];

		for (rel = 0; rel < numRelTrail; rel++)
			relBordTrail[rel] = relBorder1[rel];

		if (sbrGrid->pointer > 1)			middleBorder = sbrGrid->numEnv + 1 - sbrGrid->pointer;
		else								middleBorder = sbrGrid->numEnv - 1;

		break;
	}

	/* build time border vector */
	sbrGrid->envTimeBorder[0] = absBordLead * SAMPLES_PER_SLOT;

	rel = 0;
	border = absBordLead;
	for (env = 1; env <= numRelLead; env++) {