@@ -76,7 +76,7 @@ std::vector<int16_t> AdpcmDecoder::decode(const std::vector<char>& data, uint32_

   }

   std::vector<int16_t> sample;

   sample.reserve(length << 1);

-  for (int i = 0; i < length; i++) {

+  for (uint32_t i = 0; i < length; i++) {

     sample.push_back(getNextSample(data[offset + i] & 0x0f));

     sample.push_back(getNextSample(uint8_t(data[offset + i] & 0xf0) >> 4));

   }

new file mode 100644

@@ -0,0 +1,84 @@

+#include "adpcmdecoder.h"

+#include <iostream>

+

+template <typename T, typename T2>

+static inline T clamp(T2 value, T lower, T upper)

+{

+  return value < lower ? lower : (value > upper ? upper : value);

+}

+

+template <typename T, typename Container>

+static inline T parseInt(const Container& buffer, int offset)

+{

+  uint64_t result = 0;

+  for (int i = sizeof(T) - 1; i >= 0; --i) {

+    result = (result << 8) | uint8_t(buffer[offset + i]);

+  }

+  return T(result);

+}

+

+static const int16_t adpcmIndex[] = { -1, -1, -1, -1, 2, 4, 6, 8, };

+

+static const int16_t adpcmStep[] = {

+      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,

+};

+static const int16_t maxAdpcmStep = (sizeof(adpcmStep) >> 1) - 1;

+

+AdpcmDecoder::AdpcmDecoder(int16_t initialPredictor, int16_t initialStep)

+: predictor(initialPredictor), index(clamp<int8_t>(initialStep, 0, maxAdpcmStep))

+{

+  // initializers only

+}

+

+int16_t AdpcmDecoder::getNextSample(uint8_t value)

+{

+  int16_t step = adpcmStep[index];

+  int32_t delta = step >> 3;

+  if (value & 0x04) delta += step;

+  if (value & 0x02) delta += step >> 1;

+  if (value & 0x01) delta += step >> 2;

+  if (value & 0x08) delta = -delta;

+  /*

+  // This implementation is simpler and obeys the spec, but it suffers from low-bit rounding

+  // errors that introduce a slow DC drift that causes looping to produce pops.

+  int32_t delta = (int32_t(value & 0x08 ? -step : step) * ((value << 1 & 0x0f) + 0x01)) >> 3;

+  */

+  if (predictor + delta == -0x8000) {

+    predictor = -0x8000;

+  } else {

+    predictor = clamp<int16_t>(predictor + delta, -0x7fff, 0x7fff);

+  }

+  index = clamp<int8_t>(index + adpcmIndex[value & 0x07], 0, maxAdpcmStep);

+  return predictor;

+}

+

+std::vector<int16_t> AdpcmDecoder::decodeFile(const std::vector<char>& data, uint32_t offset, uint32_t length)

+{

+  if (!length) {

+    length = data.size() - offset;

+  }

+  AdpcmDecoder adpcm(parseInt<int16_t>(data, offset), parseInt<int16_t>(data, offset + 2));

+  return adpcm.decode(data, offset + 4, length - 4);

+}

+

+std::vector<int16_t> AdpcmDecoder::decode(const std::vector<char>& data, uint32_t offset, uint32_t length)

+{

+  if (!length) {

+    length = data.size() - offset;

+  }

+  std::vector<int16_t> sample;

+  sample.reserve(length << 1);

+  for (int i = 0; i < length; i++) {

+    sample.push_back(getNextSample(data[offset + i] & 0x0f));

+    sample.push_back(getNextSample(uint8_t(data[offset + i] & 0xf0) >> 4));

+  }

+  return sample;

+}