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Only sign-expand the nibble when needed

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Chris Robinson
2014-03-06 19:14:19 -08:00
parent 143f786d1a
commit 7657fbb296
1 changed files with 3 additions and 4 deletions
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OpenAL32/sample_cvt.c
+3 -4
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@@ -396,22 +396,21 @@ static void DecodeMSADPCMBlock(ALshort *dst, const ALmsadpcm *src, ALint numchan
const ALint num = (j*numchans) + i;
ALint nibble, pred;
/* Read the nibble and sign-expand it. */
/* Read the nibble (first is in the upper bits). */
if(!(num&1))
nibble = (*src>>4)&0x0f;
else
nibble = (*(src++))&0x0f;
nibble = (nibble^0x08) - 0x08;
pred = (samples[i][0]*MSADPCMAdaptionCoeff[blockpred[i]][0] +
samples[i][1]*MSADPCMAdaptionCoeff[blockpred[i]][1]) / 256;
pred += nibble * delta[i];
pred += ((nibble^0x08) - 0x08) * delta[i];
pred = clampi(pred, -32768, 32767);
samples[i][1] = samples[i][0];
samples[i][0] = pred;
delta[i] = (MSADPCMAdaption[nibble&0x0f] * delta[i]) / 256;
delta[i] = (MSADPCMAdaption[nibble] * delta[i]) / 256;
delta[i] = maxi(16, delta[i]);
*(dst++) = pred;