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7-8% faster decoding by rewriting GetCoeffs()

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Change-Id: Ib7c27e985d3b5222e8fa1f98cec462458caa9541
This commit is contained in:
skal 2013-09-30 23:11:51 +02:00
parent 92d47e4ca9
commit 2a98136667
1 changed files with 11 additions and 13 deletions
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22
src/dec/vp8.c
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@ -472,19 +472,20 @@ static int GetLargeValue(VP8BitReader* const br, const uint8_t* const p) {
}
// Returns the position of the last non-zero coeff plus one
// (and 0 if there's no coeff at all)
static int GetCoeffs(VP8BitReader* const br, const VP8BandProbas* const prob,
int ctx, const quant_t dq, int n, int16_t* out) {
// n is either 0 or 1 here. kBands[n] is not necessary for extracting '*p'.
const uint8_t* p = prob[n].probas_[ctx];
if (!VP8GetBit(br, p[0])) { // first EOB is more a 'CBP' bit.
return 0;
}
for (; n < 16; ++n) {
const VP8ProbaArray *p_ctx = &prob[kBands[n + 1]].probas_[0];
if (!VP8GetBit(br, p[1])) {
p = p_ctx[0];
} else { // non zero coeff
if (!VP8GetBit(br, p[0])) {
return n; // previous coeff was last non-zero coeff
}
while (!VP8GetBit(br, p[1])) { // sequence of zero coeffs
p = prob[kBands[++n]].probas_[0];
if (n == 16) return 16;
}
{ // non zero coeff
const VP8ProbaArray* const p_ctx = &prob[kBands[n + 1]].probas_[0];
int v;
if (!VP8GetBit(br, p[2])) {
v = 1;
@ -494,9 +495,6 @@ static int GetCoeffs(VP8BitReader* const br, const VP8BandProbas* const prob,
p = p_ctx[2];
}
out[kZigzag[n]] = VP8GetSigned(br, v) * dq[n > 0];
if (n < 15 && !VP8GetBit(br, p[0])) { // EOB
return n + 1;
}
}
}
return 16;
@ -539,7 +537,7 @@ static int ParseResiduals(VP8Decoder* const dec,
for (x = 0; x < 4; ++x) {
const int ctx = l + (tnz & 1);
const int nz = GetCoeffs(token_br, ac_proba, ctx, q->y1_mat_, first, dst);
l = (nz > 0);
l = (nz > first);
tnz = (tnz >> 1) | (l << 7);
nz_dc = (nz_dc << 1) | (dst[0] != 0);
nz_ac = (nz_ac << 1) | (nz > 1);