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SCUMM: Move ADPCM decoder into separate function
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@fingolfin
fingolfin committed Apr 13, 2011
1 parent 79f514a commit 29962bf
Showing 1 changed file with 127 additions and 127 deletions.
254 changes: 127 additions & 127 deletions engines/scumm/imuse_digi/dimuse_codecs.cpp
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Expand Up @@ -183,8 +183,133 @@ static int32 compDecode(byte *src, byte *dst) {
}
#undef NextBit

int32 decompressADPCM(byte *compInput, byte *compOutput, int channels) {
byte *src;

// Decoder for the the IMA ADPCM variants used in COMI.
// Contrary to regular IMA ADPCM, this codec uses a variable
// bitsize for the encoded data.

const int MAX_CHANNELS = 2;
int32 outputSamplesLeft;
int32 destPos;
int16 firstWord;
byte initialTablePos[MAX_CHANNELS] = {0, 0};
//int32 initialimcTableEntry[MAX_CHANNELS] = {7, 7};
int32 initialOutputWord[MAX_CHANNELS] = {0, 0};
int32 totalBitOffset, curTablePos, outputWord;
byte *dst;
int i;

// We only support mono and stereo
assert(channels == 1 || channels == 2);

src = compInput;
dst = compOutput;
outputSamplesLeft = 0x1000;

// Every data packet contains 0x2000 bytes of audio data
// when extracted. In order to encode bigger data sets,
// one has to split the data into multiple blocks.
//
// Every block starts with a 2 byte word. If that word is
// non-zero, it indicates the size of a block of raw audio
// data (not encoded) following it. That data we simply copy
// to the output buffer and the proceed by decoding the
// remaining data.
//
// If on the other hand the word is zero, then what follows
// are 7*channels bytes containing seed data for the decoder.
firstWord = READ_BE_UINT16(src);
src += 2;
if (firstWord != 0) {
// Copy raw data
memcpy(dst, src, firstWord);
dst += firstWord;
src += firstWord;
assert((firstWord & 1) == 0);
outputSamplesLeft -= firstWord / 2;
} else {
// Read the seed values for the decoder.
for (i = 0; i < channels; i++) {
initialTablePos[i] = *src;
src += 1;
//initialimcTableEntry[i] = READ_BE_UINT32(src);
src += 4;
initialOutputWord[i] = READ_BE_UINT32(src);
src += 4;
}
}

totalBitOffset = 0;
// The channels are encoded separately.
for (int chan = 0; chan < channels; chan++) {
// Read initial state (this makes it possible for the data stream
// to be split & spread across multiple data chunks.
curTablePos = initialTablePos[chan];
//imcTableEntry = initialimcTableEntry[chan];
outputWord = initialOutputWord[chan];

// We need to interleave the channels in the output; we achieve
// that by using a variables dest offset:
destPos = chan * 2;

const int bound = (channels == 1)
? outputSamplesLeft
: ((chan == 0)
? (outputSamplesLeft+1) / 2
: outputSamplesLeft / 2);
for (i = 0; i < bound; ++i) {
// Determine the size (in bits) of the next data packet
const int32 curTableEntryBitCount = _imcTableEntryBitCount[curTablePos];
assert(2 <= curTableEntryBitCount && curTableEntryBitCount <= 7);

// Read the next data packet
const byte *readPos = src + (totalBitOffset >> 3);
const uint16 readWord = (uint16)(READ_BE_UINT16(readPos) << (totalBitOffset & 7));
const byte packet = (byte)(readWord >> (16 - curTableEntryBitCount));

// Advance read position to the next data packet
totalBitOffset += curTableEntryBitCount;

// Decode the data packet into a delta value for the output signal.
const byte signBitMask = (1 << (curTableEntryBitCount - 1));
const byte dataBitMask = (signBitMask - 1);
const byte data = (packet & dataBitMask);

int32 delta = imcTable[curTablePos] * (2 * data + 1) >> (curTableEntryBitCount - 1);

// The topmost bit in the data packet tells is a sign bit
if ((packet & signBitMask) != 0) {
delta = -delta;
}

// Accumulate the delta onto the output data
outputWord += delta;

// Clip outputWord to 16 bit signed, and write it into the destination stream
if (outputWord > 0x7fff)
outputWord = 0x7fff;
if (outputWord < -0x8000)
outputWord = -0x8000;
WRITE_BE_UINT16(dst + destPos, outputWord);
destPos += channels << 1;

// Adjust the curTablePos
curTablePos += (int8)imxOtherTable[curTableEntryBitCount - 2][data];
if (curTablePos < 0)
curTablePos = 0;
else if (curTablePos >= ARRAYSIZE(imcTable))
curTablePos = ARRAYSIZE(imcTable) - 1;
}
}

return 0x2000;
}


int32 decompressCodec(int32 codec, byte *compInput, byte *compOutput, int32 inputSize) {
int32 outputSize, channels;
int32 outputSize;
int32 offset1, offset2, offset3, length, k, c, s, j, r, t, z;
byte *src, *t_table, *p, *ptr;
byte t_tmp1, t_tmp2;
Expand Down Expand Up @@ -506,132 +631,7 @@ int32 decompressCodec(int32 codec, byte *compInput, byte *compOutput, int32 inpu

case 13:
case 15:
if (codec == 13) {
channels = 1;
} else {
channels = 2;
}

{
// Decoder for the the IMA ADPCM variants used in COMI.
// Contrary to regular IMA ADPCM, this codec uses a variable
// bitsize for the encoded data.

const int MAX_CHANNELS = 2;
int32 outputSamplesLeft;
int32 destPos;
int16 firstWord;
byte initialTablePos[MAX_CHANNELS] = {0, 0};
//int32 initialimcTableEntry[MAX_CHANNELS] = {7, 7};
int32 initialOutputWord[MAX_CHANNELS] = {0, 0};
int32 totalBitOffset, curTablePos, outputWord;
byte *dst;
int i;

// We only support mono and stereo
assert(channels == 1 || channels == 2);

src = compInput;
dst = compOutput;
outputSize = 0x2000;
outputSamplesLeft = 0x1000;

// Every data packet contains 0x2000 bytes of audio data
// when extracted. In order to encode bigger data sets,
// one has to split the data into multiple blocks.
//
// Every block starts with a 2 byte word. If that word is
// non-zero, it indicates the size of a block of raw audio
// data (not encoded) following it. That data we simply copy
// to the output buffer and the proceed by decoding the
// remaining data.
//
// If on the other hand the word is zero, then what follows
// are 7*channels bytes containing seed data for the decoder.
firstWord = READ_BE_UINT16(src);
src += 2;
if (firstWord != 0) {
// Copy raw data
memcpy(dst, src, firstWord);
dst += firstWord;
src += firstWord;
assert((firstWord & 1) == 0);
outputSamplesLeft -= firstWord / 2;
} else {
// Read the seed values for the decoder.
for (i = 0; i < channels; i++) {
initialTablePos[i] = *src;
src += 1;
//initialimcTableEntry[i] = READ_BE_UINT32(src);
src += 4;
initialOutputWord[i] = READ_BE_UINT32(src);
src += 4;
}
}

totalBitOffset = 0;
// The channels are encoded separately.
for (int chan = 0; chan < channels; chan++) {
// Read initial state (this makes it possible for the data stream
// to be split & spread across multiple data chunks.
curTablePos = initialTablePos[chan];
//imcTableEntry = initialimcTableEntry[chan];
outputWord = initialOutputWord[chan];

// We need to interleave the channels in the output; we achieve
// that by using a variables dest offset:
destPos = chan * 2;

const int bound = (channels == 1)
? outputSamplesLeft
: ((chan == 0)
? (outputSamplesLeft+1) / 2
: outputSamplesLeft / 2);
for (i = 0; i < bound; ++i) {
// Determine the size (in bits) of the next data packet
const int32 curTableEntryBitCount = _imcTableEntryBitCount[curTablePos];
assert(2 <= curTableEntryBitCount && curTableEntryBitCount <= 7);

// Read the next data packet
const byte *readPos = src + (totalBitOffset >> 3);
const uint16 readWord = (uint16)(READ_BE_UINT16(readPos) << (totalBitOffset & 7));
const byte packet = (byte)(readWord >> (16 - curTableEntryBitCount));

// Advance read position to the next data packet
totalBitOffset += curTableEntryBitCount;

// Decode the data packet into a delta value for the output signal.
const byte signBitMask = (1 << (curTableEntryBitCount - 1));
const byte dataBitMask = (signBitMask - 1);
const byte data = (packet & dataBitMask);

int32 delta = imcTable[curTablePos] * (2 * data + 1) >> (curTableEntryBitCount - 1);

// The topmost bit in the data packet tells is a sign bit
if ((packet & signBitMask) != 0) {
delta = -delta;
}

// Accumulate the delta onto the output data
outputWord += delta;

// Clip outputWord to 16 bit signed, and write it into the destination stream
if (outputWord > 0x7fff)
outputWord = 0x7fff;
if (outputWord < -0x8000)
outputWord = -0x8000;
WRITE_BE_UINT16(dst + destPos, outputWord);
destPos += channels << 1;

// Adjust the curTablePos
curTablePos += (int8)imxOtherTable[curTableEntryBitCount - 2][data];
if (curTablePos < 0)
curTablePos = 0;
else if (curTablePos >= ARRAYSIZE(imcTable))
curTablePos = ARRAYSIZE(imcTable) - 1;
}
}
}
outputSize = decompressADPCM(compInput, compOutput, (codec == 13) ? 1 : 2);
break;

default:
Expand Down

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