#include "swf.h"#ifdef RCSIDstatic char *rcsid = "$Id: adpcm.cc,v 1.1 1998/08/31 21:52:39 olivier Exp $";#endif// This file has been rearranged from the code posted// on news:forums.macromedia.com by Jonathan Gay.// Courtesy of Macromedia//// ADPCM tables//static const int indexTable2[2] = {    -1, 2,};// Is this ok?static const int indexTable3[4] = {    -1, -1, 2, 4,};static const int indexTable4[8] = {    -1, -1, -1, -1, 2, 4, 6, 8,};static const int indexTable5[16] = { -1, -1, -1, -1, -1, -1, -1, -1, 1, 2, 4, 6, 8, 10, 13, 16,};static const int* indexTables[] = { indexTable2, indexTable3, indexTable4, indexTable5};static const int stepsizeTable[89] = {    7, 8, 9, 10, 11, 12, 13, 14, 16, 17,    19, 21, 23, 25, 28, 31, 34, 37, 41, 45,    50, 55, 60, 66, 73, 80, 88, 97, 107, 118,    130, 143, 157, 173, 190, 209, 230, 253, 279, 307,    337, 371, 408, 449, 494, 544, 598, 658, 724, 796,    876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066,    2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358,    5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,    15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767};longAdpcm::GetBits(int n){	if ( bitPos < n ) FillBuffer();	assert(bitPos >= n);	long v = ((unsigned long)bitBuf << (32-bitPos)) >> (32-n);	bitPos -= n;	return v;}longAdpcm::GetSBits(int n){	if ( bitPos < n ) FillBuffer();	assert(bitPos >= n);	long v = ((long)bitBuf << (32-bitPos)) >> (32-n);	bitPos -= n;	return v;}//// The Decompressor//// ConstructorAdpcm::Adpcm(unsigned char *buffer, long isStereo){	stereo = isStereo;	src = buffer;	nBits = 0; // flag that it is not inited	nSamples = 0;	bitPos = 0;	bitBuf = 0;}voidAdpcm::FillBuffer(){	while ( bitPos <= 24 /*&& srcSize > 0*/ ) {		bitBuf = (bitBuf<<8) | *src++;		bitPos += 8;	}}voidAdpcm::Decompress(short *dst, long n){	if ( nBits == 0 ) {		// Get the compression header		nBits = (int)GetBits(2)+2;	}	const int* indexTable = indexTables[nBits-2];	int k0 = 1 << (nBits-2);	int signmask = 1 << (nBits-1);	if ( !stereo ) {		// Optimize for mono		long		vp = valpred[0]; // maybe these can get into registers...		int		ind = index[0];		long		ns = nSamples;		while ( n-- > 0 ) {			ns++;			if ( (ns & 0xFFF) == 1 ) {				// Get a new block header				*dst++ = (short)(vp = GetSBits(16));				ind = (int)GetBits(6); // The first sample in a block does not have a delta			} else {				// Process a delta value				int delta = (int)GetBits(nBits);				// Compute difference and new predicted value				// Computes 'vpdiff = (delta+0.5)*step/4'				int step = stepsizeTable[ind];				long vpdiff = 0;				int k = k0;				do {					if ( delta & k )					vpdiff += step;					step >>= 1;					k >>= 1;				} while ( k );				vpdiff += step; // add 0.5				if ( delta & signmask ) // the sign bit					vp -= vpdiff;				else					vp += vpdiff;				// Find new index value				ind += indexTable[delta&(~signmask)];				if ( ind < 0 )					ind = 0;				else if ( ind > 88 )					ind = 88;				// clamp output value				if ( vp != (short)vp )					vp = vp < 0 ? -32768 : 32767;				/* Step 7 - Output value */				*dst++ = (short)vp;			}		}		valpred[0] = vp;		index[0] = ind;		nSamples = ns;	} else {		int sn = stereo ? 2 : 1;		// Stereo		while ( n-- > 0 ) {			nSamples++;			if ( (nSamples & 0xFFF) == 1 ) {				// Get a new block header				for ( int i = 0; i < sn; i++ ) {					*dst++ = (short)(valpred[i] = GetSBits(16));					// The first sample in a block does not have a delta					index[i] = (int)GetBits(6);				}			} else {				// Process a delta value				for ( int i = 0; i < sn; i++ ) {					int delta = (int)GetBits(nBits);					// Compute difference and new predicted value					// Computes 'vpdiff = (delta+0.5)*step/4'					int step = stepsizeTable[index[i]];					long vpdiff = 0;					int k = k0;					do {						if ( delta & k ) vpdiff += step;						step >>= 1;						k >>= 1;					} while ( k );					vpdiff += step; // add 0.5					if ( delta & signmask ) // the sign bit						valpred[i] -= vpdiff;					else						valpred[i] += vpdiff;					// Find new index value					index[i] += indexTable[delta&(~signmask)];					if ( index[i] < 0 )						index[i] = 0;					else if ( index[i] > 88 )						index[i] = 88;					// clamp output value					if ( valpred[i] != (short)valpred[i] )						valpred[i] = valpred[i] < 0 ? -32768 : 32767;					/* Step 7 - Output value */					*dst++ = (short)valpred[i];				}			}		}	}}