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Simplified common buffer reader. Implemented now unused Microsoft IMA

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ADPCM buffer reader. These folks invented ye another incompatible standard
and here it will sit #if 0'ed just for a case.

svn-id: r19164
This commit is contained in:
Eugene Sandulenko 2005-10-19 03:25:00 +00:00
parent 6d5cdb6c54
commit a050da784f
1 changed files with 37 additions and 11 deletions
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48
sound/adpcm.cpp
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@ -34,8 +34,6 @@
template <typesADPCM TYPE>
class ADPCMInputStream : public AudioStream {
private:
bool _evenPos;
byte _lastByte;
Common::SeekableReadStream *_stream;
uint32 _endpos;
@ -58,10 +56,14 @@ public:
int getRate() const { return 22050; }
};
template <>
int16 ADPCMInputStream<kADPCMOki>::decode(byte code);
template <>
int16 ADPCMInputStream<kADPCMIma>::decode(byte code);
template <typesADPCM TYPE>
ADPCMInputStream<TYPE>::ADPCMInputStream(Common::SeekableReadStream *stream, uint32 size)
: _stream(stream), _evenPos(true) {
: _stream(stream) {
_status.last = 0;
_status.stepIndex = 0;
@ -71,21 +73,45 @@ ADPCMInputStream<TYPE>::ADPCMInputStream(Common::SeekableReadStream *stream, uin
template <typesADPCM TYPE>
int ADPCMInputStream<TYPE>::readBuffer(int16 *buffer, const int numSamples) {
int samples;
byte data;
assert(numSamples % 2 == 0);
// Since we process high and low nibbles separately never check buffer end
// on low nibble
for (samples = 0; !_evenPos || samples < numSamples && !_stream->eos() && _stream->pos() < _endpos; samples++) {
if (_evenPos) {
_lastByte = _stream->readByte();
buffer[samples] = decode((_lastByte >> 4) & 0x0f);
} else {
buffer[samples] = decode(_lastByte & 0x0f);
}
_evenPos = !_evenPos;
for (samples = 0; samples < numSamples && !_stream->eos() && _stream->pos() < _endpos; samples += 2) {
data = _stream->readByte();
buffer[samples] = decode((data >> 4) & 0x0f);
buffer[samples + 1] = decode(data & 0x0f);
}
return samples;
}
// Microsoft as usual tries to implement it differently. Though we don't
// use this now
#if 0
template <>
int ADPCMInputStream<kADPCMIma>::readBuffer(int16 *buffer, const int numSamples) {
int samples;
uint32 data;
int nibble;
for (samples = 0; samples < numSamples && !_stream->eos() && _stream->pos() < _endpos;) {
for (int channel = 0; channel < 2; channel++) {
data = _stream->readUint32LE();
for (nibble = 0; nibble < 8; nibble++) {
byte k = ((data & 0xf0000000) >> 28);
buffer[samples + channel + nibble * 2] = decode(k);
data <<= 4;
}
}
samples += 16;
}
return samples;
}
#endif
// adjust the step for use on the next sample.
template <typesADPCM TYPE>
int16 ADPCMInputStream<TYPE>::stepAdjust(byte code) {