From bd49d4fd4962d28447cb6edfaba8a218cf60b2da Mon Sep 17 00:00:00 2001 From: Loren Merritt Date: Tue, 25 Sep 2007 23:31:13 +0000 Subject: optimize decode_subframe_lpc() 50%/67%/43% faster on core2/k8/p4, making flac decoding overall 24%/25%/11% faster Originally committed as revision 10586 to svn://svn.ffmpeg.org/ffmpeg/trunk --- libavcodec/flac.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) (limited to 'libavcodec/flac.c') diff --git a/libavcodec/flac.c b/libavcodec/flac.c index 74b245d0e5..d8e8813d9e 100644 --- a/libavcodec/flac.c +++ b/libavcodec/flac.c @@ -359,10 +359,25 @@ static int decode_subframe_lpc(FLACContext *s, int channel, int pred_order) s->decoded[channel][i] += sum >> qlevel; } } else { - int sum; - for (i = pred_order; i < s->blocksize; i++) + for (i = pred_order; i < s->blocksize-1; i += 2) { - sum = 0; + int c = coeffs[pred_order-1]; + int s0 = c * s->decoded[channel][i-pred_order]; + int s1 = 0; + for (j = pred_order-1; j > 0; j--) + { + int d = s->decoded[channel][i-j]; + s1 += c*d; + c = coeffs[j-1]; + s0 += c*d; + } + s0 = s->decoded[channel][i] += s0 >> qlevel; + s1 += c * s0; + s->decoded[channel][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; -- cgit v1.2.3