コード例 #1
0
static int ms_adpcm_decode_block(unsigned short *output, unsigned char *input,
  int channels, int block_size)
{
  int current_channel = 0;
  int idelta[2];
  int sample1[2];
  int sample2[2];
  int coeff1[2];
  int coeff2[2];
  int stream_ptr = 0;
  int out_ptr = 0;
  int upper_nibble = 1;
  int nibble;
  int snibble;  // signed nibble
  int predictor;

  // fetch the header information, in stereo if both channels are present
  if (input[stream_ptr] > 6)
    mp_msg(MSGT_DECAUDIO, MSGL_WARN,
      "MS ADPCM: coefficient (%d) out of range (should be [0..6])\n",
      input[stream_ptr]);
  coeff1[0] = ms_adapt_coeff1[input[stream_ptr]];
  coeff2[0] = ms_adapt_coeff2[input[stream_ptr]];
  stream_ptr++;
  if (channels == 2)
  {
    if (input[stream_ptr] > 6)
     mp_msg(MSGT_DECAUDIO, MSGL_WARN,
       "MS ADPCM: coefficient (%d) out of range (should be [0..6])\n",
       input[stream_ptr]);
    coeff1[1] = ms_adapt_coeff1[input[stream_ptr]];
    coeff2[1] = ms_adapt_coeff2[input[stream_ptr]];
    stream_ptr++;
  }

  idelta[0] = LE_16(&input[stream_ptr]);
  stream_ptr += 2;
  SE_16BIT(idelta[0]);
  if (channels == 2)
  {
    idelta[1] = LE_16(&input[stream_ptr]);
    stream_ptr += 2;
    SE_16BIT(idelta[1]);
  }

  sample1[0] = LE_16(&input[stream_ptr]);
  stream_ptr += 2;
  SE_16BIT(sample1[0]);
  if (channels == 2)
  {
    sample1[1] = LE_16(&input[stream_ptr]);
    stream_ptr += 2;
    SE_16BIT(sample1[1]);
  }

  sample2[0] = LE_16(&input[stream_ptr]);
  stream_ptr += 2;
  SE_16BIT(sample2[0]);
  if (channels == 2)
  {
    sample2[1] = LE_16(&input[stream_ptr]);
    stream_ptr += 2;
    SE_16BIT(sample2[1]);
  }

  if (channels == 1)
  {
    output[out_ptr++] = sample2[0];
    output[out_ptr++] = sample1[0];
  } else {
    output[out_ptr++] = sample2[0];
    output[out_ptr++] = sample2[1];
    output[out_ptr++] = sample1[0];
    output[out_ptr++] = sample1[1];
  }

  while (stream_ptr < block_size)
  {
    // get the next nibble
    if (upper_nibble)
      nibble = snibble = input[stream_ptr] >> 4;
    else
      nibble = snibble = input[stream_ptr++] & 0x0F;
    upper_nibble ^= 1;
    SE_4BIT(snibble);

    predictor = (
      ((sample1[current_channel] * coeff1[current_channel]) +
       (sample2[current_channel] * coeff2[current_channel])) / 256) +
      (snibble * idelta[current_channel]);
    CLAMP_S16(predictor);
    sample2[current_channel] = sample1[current_channel];
    sample1[current_channel] = predictor;
    output[out_ptr++] = predictor;

    // compute the next adaptive scale factor (a.k.a. the variable idelta)
    idelta[current_channel] =
      (ms_adapt_table[nibble] * idelta[current_channel]) / 256;
    CLAMP_ABOVE_16(idelta[current_channel]);

    // toggle the channel
    current_channel ^= channels - 1;
  }
コード例 #2
0
ファイル: ad_msadpcm.c プロジェクト: Gamer125/wiibrowser
static int ms_adpcm_decode_block(unsigned short *output, unsigned char *input,
  int channels, int block_size)
{
  int current_channel = 0;
  int coeff_idx;
  int idelta[2];
  int sample1[2];
  int sample2[2];
  int coeff1[2];
  int coeff2[2];
  int stream_ptr = 0;
  int out_ptr = 0;
  int upper_nibble = 1;
  int nibble;
  int snibble;  // signed nibble
  int predictor;

  if (channels != 1) channels = 2;
  if (block_size < 7 * channels)
    return -1;

  // fetch the header information, in stereo if both channels are present
  coeff_idx = check_coeff(input[stream_ptr]);
  coeff1[0] = ms_adapt_coeff1[coeff_idx];
  coeff2[0] = ms_adapt_coeff2[coeff_idx];
  stream_ptr++;
  if (channels == 2)
  {
    coeff_idx = check_coeff(input[stream_ptr]);
    coeff1[1] = ms_adapt_coeff1[coeff_idx];
    coeff2[1] = ms_adapt_coeff2[coeff_idx];
    stream_ptr++;
  }

  idelta[0] = LE_16(&input[stream_ptr]);
  stream_ptr += 2;
  if (channels == 2)
  {
    idelta[1] = LE_16(&input[stream_ptr]);
    stream_ptr += 2;
  }

  sample1[0] = LE_16(&input[stream_ptr]);
  stream_ptr += 2;
  if (channels == 2)
  {
    sample1[1] = LE_16(&input[stream_ptr]);
    stream_ptr += 2;
  }

  sample2[0] = LE_16(&input[stream_ptr]);
  stream_ptr += 2;
  if (channels == 2)
  {
    sample2[1] = LE_16(&input[stream_ptr]);
    stream_ptr += 2;
  }

  if (channels == 1)
  {
    output[out_ptr++] = sample2[0];
    output[out_ptr++] = sample1[0];
  } else {
    output[out_ptr++] = sample2[0];
    output[out_ptr++] = sample2[1];
    output[out_ptr++] = sample1[0];
    output[out_ptr++] = sample1[1];
  }

  while (stream_ptr < block_size)
  {
    // get the next nibble
    if (upper_nibble)
      nibble = snibble = input[stream_ptr] >> 4;
    else
      nibble = snibble = input[stream_ptr++] & 0x0F;
    upper_nibble ^= 1;
    SE_4BIT(snibble);

    // should this really be a division and not a shift?
    // coefficients were originally scaled by for, which might have
    // been an optimization for 8-bit CPUs _if_ a shift is correct
    predictor = (
      ((sample1[current_channel] * coeff1[current_channel]) +
       (sample2[current_channel] * coeff2[current_channel])) / 64) +
      (snibble * idelta[current_channel]);
    CLAMP_S16(predictor);
    sample2[current_channel] = sample1[current_channel];
    sample1[current_channel] = predictor;
    output[out_ptr++] = predictor;

    // compute the next adaptive scale factor (a.k.a. the variable idelta)
    idelta[current_channel] =
      (ms_adapt_table[nibble] * idelta[current_channel]) / 256;
    CLAMP_ABOVE_16(idelta[current_channel]);

    // toggle the channel
    current_channel ^= channels - 1;
  }