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20% faster lpc, 6% overall flac decoding 

Originally committed as revision 10627 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Loren Merritt 2007-09-30 03:01:56 +00:00
parent 08965b22e2
commit d1a5c4216c
1 changed files with 18 additions and 15 deletions
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33
libavcodec/flac.c
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@ -315,6 +315,7 @@ static int decode_subframe_lpc(FLACContext *s, int channel, int pred_order)
int i, j;
int coeff_prec, qlevel;
int coeffs[pred_order];
int32_t *decoded = s->decoded[channel];
// av_log(s->avctx, AV_LOG_DEBUG, " SUBFRAME LPC\n");
@ -323,8 +324,8 @@ static int decode_subframe_lpc(FLACContext *s, int channel, int pred_order)
for (i = 0; i < pred_order; i++)
{
s->decoded[channel][i] = get_sbits(&s->gb, s->curr_bps);
// av_log(s->avctx, AV_LOG_DEBUG, " %d: %d\n", i, s->decoded[channel][i]);
decoded[i] = get_sbits(&s->gb, s->curr_bps);
// av_log(s->avctx, AV_LOG_DEBUG, " %d: %d\n", i, decoded[i]);
}
coeff_prec = get_bits(&s->gb, 4) + 1;
@ -356,32 +357,34 @@ static int decode_subframe_lpc(FLACContext *s, int channel, int pred_order)
{
sum = 0;
for (j = 0; j < pred_order; j++)
sum += (int64_t)coeffs[j] * s->decoded[channel][i-j-1];
s->decoded[channel][i] += sum >> qlevel;
sum += (int64_t)coeffs[j] * decoded[i-j-1];
decoded[i] += sum >> qlevel;
}
} else {
for (i = pred_order; i < s->blocksize-1; i += 2)
{
int c = coeffs[pred_order-1];
int s0 = c * s->decoded[channel][i-pred_order];
int s1 = 0;
int c;
int d = decoded[i-pred_order];
int s0 = 0, s1 = 0;
for (j = pred_order-1; j > 0; j--)
{
int d = s->decoded[channel][i-j];
s1 += c*d;
c = coeffs[j-1];
c = coeffs[j];
s0 += c*d;
d = decoded[i-j];
s1 += c*d;
}
s0 = s->decoded[channel][i] += s0 >> qlevel;
s1 += c * s0;
s->decoded[channel][i+1] += s1 >> qlevel;
c = coeffs[0];
s0 += c*d;
d = decoded[i] += s0 >> qlevel;
s1 += c*d;
decoded[i+1] += s1 >> qlevel;
}
if (i < s->blocksize)
{
int sum = 0;
for (j = 0; j < pred_order; j++)
sum += coeffs[j] * s->decoded[channel][i-j-1];
s->decoded[channel][i] += sum >> qlevel;
sum += coeffs[j] * decoded[i-j-1];
decoded[i] += sum >> qlevel;
}
}