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MSADPCM cleanup

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This commit is contained in:
bnnm 2021-06-20 17:29:41 +02:00
parent af3851afff
commit 3fa029ef19
1 changed files with 62 additions and 57 deletions
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117
src/coding/msadpcm_decoder.c
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@ -22,14 +22,64 @@ static const int16_t msadpcm_coefs[7][2] = {
{ 392, -232 }
};
/* Decodes MSADPCM as explained in the spec (RIFFNEW / msadpcm.c).
* Though RIFFNEW spec uses "predictor / 256", msadpcm.c uses "predictor >> 8" = diffs on negs (silly MS).
* SHR is also true in Windows msadp32.acm decoders (up to Win10), that seem to use same code.
* Some non-Windows implementations or engines (like UE4) use DIV though (more accurate).
/* Decodes MSADPCM as explained in the spec (RIFFNEW doc + msadpcm.c).
* Though RIFFNEW writes "predictor / 256" (DIV), msadpcm.c uses "predictor >> 8" (SHR). They may seem the
* same but on negative values SHR gets different results (-128 / 256 = 0; -128 >> 8 = 1) = some output diffs.
* SHR is true in Windows msadp32.acm decoders (up to Win10), while some non-Windows implementations or
* engines (like UE4) use DIV though (more accurate).
*
* On invalid coef index, msadpcm.c returns 0 decoded samples but here we clamp and keep on trucking.
* In theory blocks may be 0-padded and should use samples_per_frame from header, in practice seems to
* decode up to block length or available data. */
static int16_t msadpcm_adpcm_expand_nibble_shr(VGMSTREAMCHANNEL* stream, uint8_t byte, int shift) {
int32_t hist1, hist2, predicted;
int code = (shift) ?
get_high_nibble_signed(byte) :
get_low_nibble_signed (byte);
hist1 = stream->adpcm_history1_16;
hist2 = stream->adpcm_history2_16;
predicted = hist1 * stream->adpcm_coef[0] + hist2 * stream->adpcm_coef[1];
predicted = predicted >> 8; /* 256 = FIXED_POINT_COEF_BASE (uses SHR instead) */
predicted = predicted + (code * stream->adpcm_scale);
predicted = clamp16(predicted); /* lNewSample */
stream->adpcm_history2_16 = stream->adpcm_history1_16;
stream->adpcm_history1_16 = predicted;
stream->adpcm_scale = (msadpcm_steps[code & 0xf] * stream->adpcm_scale) >> 8; /* not diffs vs DIV here (always >=0) */
if (stream->adpcm_scale < 16) /* min delta */
stream->adpcm_scale = 16;
return predicted;
}
static int16_t msadpcm_adpcm_expand_nibble_div(VGMSTREAMCHANNEL* stream, uint8_t byte, int shift) {
int32_t hist1, hist2, predicted;
int code = (shift) ?
get_high_nibble_signed(byte) :
get_low_nibble_signed (byte);
hist1 = stream->adpcm_history1_16;
hist2 = stream->adpcm_history2_16;
predicted = hist1 * stream->adpcm_coef[0] + hist2 * stream->adpcm_coef[1];
predicted = predicted / 256; /* 256 = FIXED_POINT_COEF_BASE */
predicted = predicted + (code * stream->adpcm_scale);
predicted = clamp16(predicted); /* lNewSample */
stream->adpcm_history2_16 = stream->adpcm_history1_16;
stream->adpcm_history1_16 = predicted;
stream->adpcm_scale = (msadpcm_steps[code & 0xf] * stream->adpcm_scale) / 256; /* 256 = FIXED_POINT_ADAPTION_BASE */
if (stream->adpcm_scale < 16) /* min delta */
stream->adpcm_scale = 16;
return predicted;
}
void decode_msadpcm_stereo(VGMSTREAM* vgmstream, sample_t* outbuf, int32_t first_sample, int32_t samples_to_do) {
VGMSTREAMCHANNEL *stream1, *stream2;
uint8_t frame[MSADPCM_MAX_BLOCK_SIZE] = {0};
@ -85,25 +135,10 @@ void decode_msadpcm_stereo(VGMSTREAM* vgmstream, sample_t* outbuf, int32_t first
for (ch = 0; ch < 2; ch++) {
VGMSTREAMCHANNEL* stream = &vgmstream->ch[ch];
int32_t hist1, hist2, predicted;
uint8_t byte = get_u8(frame+0x07*2+(i-2));
int sample_nibble = (ch == 0) ? /* L = high nibble first (iErrorDelta) */
get_high_nibble_signed(byte) :
get_low_nibble_signed (byte);
hist1 = stream->adpcm_history1_16;
hist2 = stream->adpcm_history2_16;
predicted = hist1 * stream->adpcm_coef[0] + hist2 * stream->adpcm_coef[1];
predicted = predicted / 256; /* 256 = FIXED_POINT_COEF_BASE (though MS code uses SHR) */
predicted = predicted + (sample_nibble * stream->adpcm_scale);
outbuf[0] = clamp16(predicted); /* lNewSample */
stream->adpcm_history2_16 = stream->adpcm_history1_16;
stream->adpcm_history1_16 = outbuf[0];
stream->adpcm_scale = (msadpcm_steps[sample_nibble & 0xf] * stream->adpcm_scale) / 256; /* 256 = FIXED_POINT_ADAPTION_BASE */
if (stream->adpcm_scale < 16) /* min delta */
stream->adpcm_scale = 16;
int shift = (ch == 0); /* L = high nibble first (iErrorDelta) */
outbuf[0] = msadpcm_adpcm_expand_nibble_div(stream, byte, shift);
outbuf++;
}
}
@ -150,25 +185,10 @@ void decode_msadpcm_mono(VGMSTREAM* vgmstream, sample_t* outbuf, int channelspac
/* decode nibbles */
for (i = first_sample; i < first_sample + samples_to_do; i++) {
int32_t hist1, hist2, predicted;
uint8_t byte = get_u8(frame+0x07+(i-2)/2);
int sample_nibble = (i & 1) ? /* high nibble first */
get_low_nibble_signed (byte) :
get_high_nibble_signed(byte);
hist1 = stream->adpcm_history1_16;
hist2 = stream->adpcm_history2_16;
predicted = hist1 * stream->adpcm_coef[0] + hist2 * stream->adpcm_coef[1];
predicted = predicted / 256;
predicted = predicted + (sample_nibble * stream->adpcm_scale);
outbuf[0] = clamp16(predicted);
stream->adpcm_history2_16 = stream->adpcm_history1_16;
stream->adpcm_history1_16 = outbuf[0];
stream->adpcm_scale = (msadpcm_steps[sample_nibble & 0xf] * stream->adpcm_scale) / 256;
if (stream->adpcm_scale < 16) /* min delta */
stream->adpcm_scale = 16;
int shift = !(i & 1); /* high nibble first */
outbuf[0] = msadpcm_adpcm_expand_nibble_div(stream, byte, shift);
outbuf += channelspacing;
}
}
@ -216,25 +236,10 @@ void decode_msadpcm_ck(VGMSTREAM* vgmstream, sample_t* outbuf, int channelspacin
/* decode nibbles */
for (i = first_sample; i < first_sample + samples_to_do; i++) {
int32_t hist1,hist2, predicted;
uint8_t byte = get_u8(frame+0x07+(i-2)/2);
int sample_nibble = (i & 1) ? /* low nibble first, unlike normal MSADPCM */
get_high_nibble_signed(byte) :
get_low_nibble_signed (byte);
hist1 = stream->adpcm_history1_16;
hist2 = stream->adpcm_history2_16;
predicted = hist1 * stream->adpcm_coef[0] + hist2 *stream->adpcm_coef[1];
predicted = predicted >> 8; /* not DIV unlike spec */
predicted = predicted + (sample_nibble * stream->adpcm_scale);
outbuf[0] = clamp16(predicted);
stream->adpcm_history2_16 = stream->adpcm_history1_16;
stream->adpcm_history1_16 = outbuf[0];
stream->adpcm_scale = (msadpcm_steps[sample_nibble & 0xf] * stream->adpcm_scale) >> 8; /* not DIV but same here (always >=0) */
if (stream->adpcm_scale < 16)
stream->adpcm_scale = 16;
int shift = (i & 1); /* low nibble first, unlike normal MSADPCM */
outbuf[0] = msadpcm_adpcm_expand_nibble_shr(stream, byte, shift);
outbuf += channelspacing;
}
}