blkdec.cpp

此源码是在VC平台下,实现MPEG4编解码的源码

			}
			else 
			{ // MPEG-4
					decodeIntraVLCtableIndex (lIndex, iLevel, iRun, bIsLastRun);
					
			}
				
		}
		else	{
			decodeEscape (iLevel, iRun, bIsLastRun, g_rgiLMAXintra, g_rgiRMAXintra, 
						  m_pentrdecSet->m_pentrdecDCTIntra, CVideoObjectDecoder::decodeIntraVLCtableIndex);
		}
		//fprintf(stderr,"%d %d %d %d\n", lIndex,iLevel,iRun,bIsLastRun);
		for (Int i = 0; i < iRun; i++)	{
			rgiCoefQ [rgiZigzag [iCoef]] = 0;
			iCoef++;
		}
		rgiCoefQ [rgiZigzag [iCoef]] = iLevel;			
		iCoef++;
	}															
	for (Int i = iCoef; i < BLOCK_SQUARE_SIZE; i++)			// fill the rest w/ zero
		rgiCoefQ [rgiZigzag [i]]  = 0;
}

Void CVideoObjectDecoder::decodeEscape (Int& iLevel, Int& iRun, Int& bIsLastRun, const Int* rgiLMAX, const Int* rgiRMAX, 
				   CEntropyDecoder* pentrdec, DECODE_TABLE_INDEX decodeVLCtableIndex)
{
	//	Modified by Toshiba(1997-11-14)
	if (!short_video_header) { // Added bij KPN [FDS]
	if (m_pbitstrmIn->getBits (1) == 0)	{				//vlc; Level+
	//if (m_pbitstrmIn->getBits (1) == 1)	{				//vlc; Level+
	//	End Toshiba(1997-11-14)
		Int iIndex = pentrdec->decodeSymbol();
		(this->*decodeVLCtableIndex) (iIndex, iLevel, iRun, bIsLastRun);
		//get level back
		Int iLevelPlusAbs = abs (iLevel);
		Int iLevelAbs = iLevelPlusAbs + rgiLMAX [(iRun & 0x0000003F) + (bIsLastRun << 6)];		//hashing the table
		iLevel = sign(iLevel) * iLevelAbs;
	}
	//	Modified Toshiba(1997-11-14)
	else if (m_pbitstrmIn->getBits (1) == 0) {			//vlc; Run+
	//else if (m_pbitstrmIn->getBits (1) == 1) {			//vlc; Run+
	//	End Toshiba(1997-11-14)
		Int iIndex = pentrdec->decodeSymbol();
		(this->*decodeVLCtableIndex) (iIndex, iLevel, iRun, bIsLastRun);		
		iRun = iRun + rgiRMAX [(abs(iLevel) & 0x0000001F) + (bIsLastRun << 5)];	//get run back; RMAX tabl incl. + 1 already
	}
	else {												//flc
		bIsLastRun = (Bool) m_pbitstrmIn->getBits (1);		
		iRun =	(Int) m_pbitstrmIn->getBits (NUMBITS_ESC_RUN);			
		assert (iRun < BLOCK_SQUARE_SIZE);\
		Int iLevelBits = 12; // = m_volmd.nBits;
		Int iMarker = m_pbitstrmIn->getBits (1);
		assert(iMarker == 1);
		iLevel = (Int) m_pbitstrmIn->getBits (iLevelBits);
		iMarker = m_pbitstrmIn->getBits (1);
		assert(iMarker == 1);
		Int iMaxAC = (1<<(iLevelBits-1)) - 1;
		assert(iLevel!=iMaxAC+1);
		if (iLevel > iMaxAC)
			iLevel -= (1<<iLevelBits);
		assert(iLevel != 0);
	}
	} // Escape coding short headers. Added by KPN
	else
	{
		bIsLastRun = (Bool) m_pbitstrmIn->getBits (1);
		iRun = (Int) m_pbitstrmIn->getBits (6);
		int iLevelIndex = (Int) m_pbitstrmIn->getBits(8);
		if (iLevelIndex==0||iLevelIndex==128) 
		{
			fprintf(stderr,"Short header mode. Levels 0 and 128 are not allowed\n");
			exit(2);
		}
		if (iLevelIndex >=0 && iLevelIndex <128) 
		{
			iLevel=iLevelIndex;
		} else 
		{
			iLevel=iLevelIndex-256;
		}
	}
}

Void CVideoObjectDecoder::decodeInterTCOEF (Int* rgiCoefQ, Int iCoefStart, Int* rgiZigzag)
{
	Bool bIsLastRun = FALSE;
	Int  iRun = 0;
	Int	 iLevel = 0;
	Int  iCoef = iCoefStart;
	Long lIndex;
	while (!bIsLastRun) {
		lIndex = m_pentrdecSet->m_pentrdecDCT->decodeSymbol();
		if (lIndex != TCOEF_ESCAPE)	{							// if Huffman
			decodeInterVLCtableIndex (lIndex, iLevel, iRun, bIsLastRun);
			assert (iRun < BLOCK_SQUARE_SIZE);
		}
		else
			decodeEscape (iLevel, iRun, bIsLastRun, g_rgiLMAXinter, g_rgiRMAXinter, 
						  m_pentrdecSet->m_pentrdecDCT, CVideoObjectDecoder::decodeInterVLCtableIndex);
		for (Int i = 0; i < iRun; i++)	{
			rgiCoefQ [rgiZigzag [iCoef]] = 0;
			iCoef++;
		}
		rgiCoefQ [rgiZigzag [iCoef]] = iLevel;			
		iCoef++;
	}															
	for (Int i = iCoef; i < BLOCK_SQUARE_SIZE; i++)					// fill the rest w/ zero
		rgiCoefQ [rgiZigzag [i]]  = 0;
}


Void CVideoObjectDecoder::decodeIntraVLCtableIndex  (Int iIndex, Int& iLevel, Int& iRun, Int& bIsLastRun)
{
	static Int iLevelMask = 0x0000001F;
	static Int iRunMask = 0x000003E0;
	static Int iLastRunMask = 0x00000400;
	iLevel = iLevelMask & grgiIntraYAVCLHashingTable [iIndex];
	iRun = (iRunMask & grgiIntraYAVCLHashingTable [iIndex]) >> 5;
	bIsLastRun = (iLastRunMask  & grgiIntraYAVCLHashingTable [iIndex]) >> 10;
	if (m_pentrdecSet->m_pentrdecDCT->bitstream()->getBits (1) == TRUE)	// get signbit
		iLevel = -iLevel;
	assert (iRun < BLOCK_SQUARE_SIZE);
}

															
Void CVideoObjectDecoder::decodeInterVLCtableIndex (Int   iIndex, Int& iLevel,		// return islastrun, run and level													 
													Int&  iRun, Bool& bIsLastRun)
{	
	assert (iIndex >= 0 && iIndex < 102);
	bIsLastRun = FALSE;
	Int iIndexLeft = (Int) iIndex;
	if (iIndex >= 58)	{
		iIndexLeft -= 58;
		bIsLastRun = TRUE;
	}
	iRun = 0;
	while (iIndexLeft >= 0)	{
		if (!bIsLastRun)
			iIndexLeft -= grgIfNotLastNumOfLevelAtRun [iRun];
		else
			iIndexLeft -= grgIfLastNumOfLevelAtRun [iRun];
		iRun++;
	}
	assert (iRun > 0);
	iRun--;
	if (!bIsLastRun)
		iLevel = iIndexLeft + grgIfNotLastNumOfLevelAtRun [iRun] + 1;
	else
		iLevel = iIndexLeft + grgIfLastNumOfLevelAtRun [iRun] + 1;	
	assert (iRun >= 0);
	if (m_pentrdecSet->m_pentrdecDCT->bitstream()->getBits (1) == TRUE)	// get signbit
		iLevel = -iLevel;
}

Int CVideoObjectDecoder::decodeIntraDCmpeg (Bool bIsYBlk)
{
	Long lSzDiffIntraDC;
	if (bIsYBlk)
		lSzDiffIntraDC = m_pentrdecSet->m_pentrdecIntraDCy->decodeSymbol();
	else 
		lSzDiffIntraDC = m_pentrdecSet->m_pentrdecIntraDCc->decodeSymbol();
	Int iDiffIntraDC = 0;
	if (lSzDiffIntraDC !=0 )	{
	    if (lSzDiffIntraDC<=8) { // NBIT
		U8 chDiffIntraDC = 
			(U8) m_pentrdecSet->m_pentrdecIntraDCy->bitstream()->getBits (lSzDiffIntraDC);	
		if (!((1 << (lSzDiffIntraDC - 1)) & chDiffIntraDC))
			iDiffIntraDC = -1 * ((0x00FF >> (8 - lSzDiffIntraDC)) & (~chDiffIntraDC));
		else
			iDiffIntraDC = (Int) chDiffIntraDC;
	    } else { // NBIT - marker bit inserted after 8 bits
/*
		UInt uiDiffIntraDC =
			(UInt) m_pentrdecSet->m_pentrdecIntraDCy->bitstream()->getBits (lSzDiffIntraDC+1);
			Int iOffset = lSzDiffIntraDC-8;
			uiDiffIntraDC = ( uiDiffIntraDC>>(iOffset+1)<<iOffset )
				      + ( uiDiffIntraDC & ((1<<iOffset)-1) );
*/
			UInt uiDiffIntraDC =
				(UInt) m_pentrdecSet->m_pentrdecIntraDCy->bitstream()->getBits (lSzDiffIntraDC);
			if (!((1 << (lSzDiffIntraDC - 1)) & uiDiffIntraDC))
				iDiffIntraDC = -1 * ((0xFFFF >> (16 - lSzDiffIntraDC)) & (~uiDiffIntraDC));
			else
				iDiffIntraDC = (Int) uiDiffIntraDC;
			m_pentrdecSet->m_pentrdecIntraDCy->bitstream()->getBits (1);
	    }
	}
	return iDiffIntraDC;
}

Void CVideoObjectDecoder::inverseDCACPred (const CMBMode* pmbmd, Int iBlkIdx,
										   Int* rgiCoefQ, Int iQP,
										   Int iDcScaler,
										   const BlockMemory blkmPred,
										   Int iQpPred)
{
	UInt nBits = m_volmd.nBits; // NBIT
	Int iDefVal = 1<<(nBits+2); // NBIT

	//do DC prediction
	if (!short_video_header)
	{		// Added by KPN for short video headers
		if (blkmPred == NULL)
			rgiCoefQ [0] += divroundnearest(iDefVal, iDcScaler);
		else {
			rgiCoefQ [0] += divroundnearest(blkmPred [0], iDcScaler);
			// clip range after inverse pred
			rgiCoefQ [0] = rgiCoefQ[0] < -2048 ? -2048 : (rgiCoefQ[0] > 2047 ? 2047 : rgiCoefQ[0]);
			if (iBlkIdx<(A_BLOCK1 - 1) && pmbmd->m_bACPrediction
				|| iBlkIdx>=(A_BLOCK1 - 1) && pmbmd->m_bACPredictionAlpha)	{
				Int i, j;
				//do AC prediction
				if (pmbmd->m_preddir [iBlkIdx] == HORIZONTAL)	{
					for (i = 8, j = 8; j < 2 * BLOCK_SIZE - 1; i += 8, j++)
					{
						rgiCoefQ [i] += (blkmPred == NULL) ? 0 : (iQP == iQpPred) ?
										 blkmPred [j] : divroundnearest(blkmPred [j] * iQpPred, iQP);
						// clip range after inverse pred
						rgiCoefQ [i] = rgiCoefQ[i] < -2048 ? -2048 : (rgiCoefQ[i] > 2047 ? 2047 : rgiCoefQ[i]);
					}

				}
				else if  (pmbmd->m_preddir [iBlkIdx] == VERTICAL)	{
					//horizontal zigzag scan
					for (i = 1; i < BLOCK_SIZE; i++)
					{
						rgiCoefQ [i] += (blkmPred == NULL) ? 0 : (iQP == iQpPred) ?
										 blkmPred [i] : divroundnearest(blkmPred [i] * iQpPred, iQP);
						// clip range after inverse pred
						rgiCoefQ [i] = rgiCoefQ[i] < -2048 ? -2048 : (rgiCoefQ[i] > 2047 ? 2047 : rgiCoefQ[i]);
					}
				}
				else
					assert (FALSE);
			}
		}
	}// End short video headers
}