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#include "swf.h"
#ifdef RCSID
static char *rcsid = "$Id$";
#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
};
long
Adpcm::GetBits(int n)
{
if ( bitPos < n ) FillBuffer();
assert(bitPos >= n);
long v = ((unsigned long)bitBuf << (32-bitPos)) >> (32-n);
bitPos -= n;
return v;
}
long
Adpcm::GetSBits(int n)
{
if ( bitPos < n ) FillBuffer();
assert(bitPos >= n);
long v = ((long)bitBuf << (32-bitPos)) >> (32-n);
bitPos -= n;
return v;
}
//
// The Decompressor
//
// Constructor
Adpcm::Adpcm(unsigned char *buffer, long isStereo)
{
stereo = isStereo;
src = buffer;
nBits = 0; // flag that it is not inited
nSamples = 0;
bitPos = 0;
bitBuf = 0;
}
void
Adpcm::FillBuffer()
{
while ( bitPos <= 24 /*&& srcSize > 0*/ ) {
bitBuf = (bitBuf<<8) | *src++;
bitPos += 8;
}
}
void
Adpcm::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];
}
}
}
}
}
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