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/*
Unified ADPCM Decoder for MPlayer
(C) 2001 Mike Melanson
*/
#include "config.h"
#include "bswap.h"
#include "adpcm.h"
#define BE_16(x) (be2me_16(*(unsigned short *)(x)))
#define BE_32(x) (be2me_32(*(unsigned int *)(x)))
#define LE_16(x) (le2me_16(*(unsigned short *)(x)))
#define LE_32(x) (le2me_32(*(unsigned int *)(x)))
// clamp a number between 0 and 88
#define CLAMP_0_TO_88(x) if (x < 0) x = 0; else if (x > 88) x = 88;
// clamp a number within a signed 16-bit range
#define CLAMP_S16(x) if (x < -32768) x = -32768; \
else if (x > 32767) x = 32767;
// sign extend a 16-bit value
#define SE_16BIT(x) if (x & 0x8000) x -= 0x10000;
void ima_dvi_decode_nibbles(unsigned short *output, int channels,
int predictor_l, int index_l,
int predictor_r, int index_r)
{
int step[2];
int predictor[2];
int index[2];
int diff;
int i;
int sign;
int delta;
int channel_number = 0;
step[0] = adpcm_step[index_l];
step[1] = adpcm_step[index_r];
predictor[0] = predictor_l;
predictor[1] = predictor_r;
index[0] = index_l;
index[1] = index_r;
for (i = 0; i < IMA_ADPCM_SAMPLES_PER_BLOCK * channels; i++)
{
delta = output[i];
index[channel_number] += adpcm_index[delta];
CLAMP_0_TO_88(index[channel_number]);
sign = delta & 8;
delta = delta & 7;
diff = step[channel_number] >> 3;
if (delta & 4) diff += step[channel_number];
if (delta & 2) diff += step[channel_number] >> 1;
if (delta & 1) diff += step[channel_number] >> 2;
if (sign)
predictor[channel_number] -= diff;
else
predictor[channel_number] += diff;
CLAMP_S16(predictor[channel_number]);
output[i] = predictor[channel_number];
step[channel_number] = adpcm_step[index[channel_number]];
// toggle channel
channel_number ^= channels - 1;
}
}
int ima_adpcm_decode_block(unsigned short *output, unsigned char *input,
int channels)
{
int initial_predictor_l = 0;
int initial_predictor_r = 0;
int initial_index_l = 0;
int initial_index_r = 0;
int i;
initial_predictor_l = BE_16(&input[0]);
initial_index_l = initial_predictor_l;
// mask, sign-extend, and clamp the predictor portion
initial_predictor_l &= 0xFF80;
SE_16BIT(initial_predictor_l);
CLAMP_S16(initial_predictor_l);
// mask and clamp the index portion
initial_index_l &= 0x7F;
CLAMP_0_TO_88(initial_index_l);
// handle stereo
if (channels > 1)
{
initial_predictor_r = BE_16(&input[IMA_ADPCM_BLOCK_SIZE]);
initial_index_r = initial_predictor_r;
// mask, sign-extend, and clamp the predictor portion
initial_predictor_r &= 0xFF80;
SE_16BIT(initial_predictor_r);
CLAMP_S16(initial_predictor_r);
// mask and clamp the index portion
initial_index_r &= 0x7F;
CLAMP_0_TO_88(initial_index_r);
}
// break apart all of the nibbles in the block
if (channels == 1)
for (i = 0; i < IMA_ADPCM_SAMPLES_PER_BLOCK / 2; i++)
{
output[i * 2 + 0] = input[2 + i] & 0x0F;
output[i * 2 + 1] = input[2 + i] >> 4;
}
else
for (i = 0; i < IMA_ADPCM_SAMPLES_PER_BLOCK / 2 * 2; i++)
{
output[i * 4 + 0] = input[2 + i] & 0x0F;
output[i * 4 + 1] = input[2 + IMA_ADPCM_BLOCK_SIZE + i] & 0x0F;
output[i * 4 + 2] = input[2 + i] >> 4;
output[i * 4 + 3] = input[2 + IMA_ADPCM_BLOCK_SIZE + i] >> 4;
}
ima_dvi_decode_nibbles(output, channels,
initial_predictor_l, initial_index_l,
initial_predictor_r, initial_index_r);
return IMA_ADPCM_SAMPLES_PER_BLOCK * channels;
}
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