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#ifndef USNG_ADPCM_H
#define USNG_ADPCM_H
#include <iostream>
#include <stdexcept>
#include <vector>
class Adpcm {
public:
/** Initialize the decoder.
* Typical values for interleave are 0xB800 and 0xBB80. This information can
* be extracted from music.mih
**/
Adpcm(unsigned int interleave_, unsigned int channels_ = 2): m_interleave(interleave_), headers(channels_) {}
/** Decode 16 bytes of each channel, outputting 28 samples/ch. **/
template <typename OutIt> OutIt decodeBlock(char const* data, OutIt pcm) {
// Read headers
for (unsigned ch = 0; ch < headers.size(); ++ch) headers[ch].parse(data + ch * m_interleave);
for (unsigned n = 0; n < 28; ++n) {
for (unsigned ch = 0; ch < headers.size(); ++ch) {
Header& h = headers[ch];
// Get a nibble and left-align it
short sample = (data[2 + n / 2 + ch * m_interleave] << (n % 2 ? 8 : 12)) & 0xF000;
int i_sample = sample;
// Apply ADPCM exponent
i_sample >>= h.shift;
// Apply prediction
i_sample += (h.pr1 * h.prev1 + h.pr2 * h.prev2 + 32) >> 6;
if( i_sample > 32767 ) {
sample = 32767;
} else if( i_sample < -32768 ) {
sample = -32768;
} else {
sample = i_sample;
}
// Store history for prediction
h.prev2 = h.prev1;
h.prev1 = sample;
// Output sample
*pcm++ = sample;
}
}
return pcm;
}
unsigned int chunkFrames() const { return m_interleave / 16 * 28; }
unsigned int chunkBytes() const { return m_interleave * 2; }
void interleave(unsigned int _interleave) {m_interleave = _interleave; }
/** Decode chunkBytes() bytes, outputting chunkFrames() samples/ch. **/
template <typename OutIt> OutIt decodeChunk(char const* data, OutIt pcm) {
for (unsigned pos = 0; pos < m_interleave; pos += 16) pcm = decodeBlock(data + pos, pcm);
return pcm;
}
private:
unsigned int m_interleave;
struct Header {
Header(): prev1(), prev2() {}
int shift;
int pr1;
int pr2;
char loopend;
char loop;
char loopstart;
short prev1;
short prev2;
void parse(char const* data) {
static const int f[5][2] = { { 0, 0 }, { 60, 0 }, { 115, -52 }, { 98, -55 }, { 122, -60 } };
shift = data[0] & 0xF;
unsigned mode = (data[0] >> 4) & 0xF;
if (mode >= 5) throw std::runtime_error("Invalid mode");
pr1 = f[mode][0];
pr2 = f[mode][1];
loopend = data[1] & 1;
loop = (data[1] >> 1) & 1;
loopstart = (data[1] >> 2) & 1;
}
};
std::vector<Header> headers;
};
#endif
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