[FFmpeg-cvslog] r10624 - trunk/libavcodec/flacenc.c
lorenm
subversion
Sun Sep 30 01:21:57 CEST 2007
Author: lorenm
Date: Sun Sep 30 01:21:57 2007
New Revision: 10624
Log:
encode_residual_fixed(): replace FIR with finite differences.
4x faster order 2, 3.5x order 3, 3x order 4.
overall flac encoding: 35% faster at compression_levels 0-2, no effect at higher levels.
Modified:
trunk/libavcodec/flacenc.c
Modified: trunk/libavcodec/flacenc.c
==============================================================================
--- trunk/libavcodec/flacenc.c (original)
+++ trunk/libavcodec/flacenc.c Sun Sep 30 01:21:57 2007
@@ -840,14 +840,35 @@ static void encode_residual_fixed(int32_
for(i=order; i<n; i++)
res[i]= smp[i] - smp[i-1];
}else if(order==2){
- for(i=order; i<n; i++)
- res[i]= smp[i] - 2*smp[i-1] + smp[i-2];
+ int a = smp[order-1] - smp[order-2];
+ for(i=order; i<n; i++) {
+ int b = smp[i] - smp[i-1];
+ res[i]= b - a;
+ a = b;
+ }
}else if(order==3){
- for(i=order; i<n; i++)
- res[i]= smp[i] - 3*smp[i-1] + 3*smp[i-2] - smp[i-3];
+ int a = smp[order-1] - smp[order-2];
+ int c = smp[order-1] - 2*smp[order-2] + smp[order-3];
+ for(i=order; i<n; i++) {
+ int b = smp[i] - smp[i-1];
+ int d = b - a;
+ res[i]= d - c;
+ a = b;
+ c = d;
+ }
}else{
- for(i=order; i<n; i++)
- res[i]= smp[i] - 4*smp[i-1] + 6*smp[i-2] - 4*smp[i-3] + smp[i-4];
+ int a = smp[order-1] - smp[order-2];
+ int c = smp[order-1] - 2*smp[order-2] + smp[order-3];
+ int e = smp[order-1] - 3*smp[order-2] + 3*smp[order-3] - smp[order-4];
+ for(i=order; i<n; i++) {
+ int b = smp[i] - smp[i-1];
+ int d = b - a;
+ int f = d - c;
+ res[i]= f - e;
+ a = b;
+ c = d;
+ e = f;
+ }
}
}
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