From c5f3033a863817eca589b34d4872301dfcaee3d7 Mon Sep 17 00:00:00 2001 From: Niklas Haas Date: Thu, 12 Jun 2025 17:42:37 +0200 Subject: [PATCH] avfilter/f_ebur128: use transformed direct form II Instead of direct form I. See af_biquads.c for math. Also eliminate an unnecessary indirection. --- libavfilter/f_ebur128.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/libavfilter/f_ebur128.c b/libavfilter/f_ebur128.c index 768f062bac..173a4f75ca 100644 --- a/libavfilter/f_ebur128.c +++ b/libavfilter/f_ebur128.c @@ -686,17 +686,15 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *insamples) /* Y[i] = X[i]*b0 + X[i-1]*b1 + X[i-2]*b2 - Y[i-1]*a1 - Y[i-2]*a2 */ #define FILTER(Y, X, NUM, DEN) do { \ double *dst = ebur128->Y + ch*3; \ - double *src = ebur128->X + ch*3; \ - dst[2] = dst[1]; \ - dst[1] = dst[0]; \ - dst[0] = src[0]*NUM[0] + src[1]*NUM[1] + src[2]*NUM[2] \ - - dst[1]*DEN[1] - dst[2]*DEN[2]; \ + double src = ebur128->X[ch*3] ; \ + double dst0 = NUM[0] * src + dst[1]; \ + dst[1] = NUM[1] * src + dst[2] - DEN[1] * dst0; \ + dst[2] = NUM[2] * src - DEN[2] * dst0; \ + dst[0] = dst0; \ } while (0) // TODO: merge both filters in one? FILTER(y, x, ebur128->pre_b, ebur128->pre_a); // apply pre-filter - ebur128->x[ch * 3 + 2] = ebur128->x[ch * 3 + 1]; - ebur128->x[ch * 3 + 1] = ebur128->x[ch * 3 ]; FILTER(z, y, ebur128->rlb_b, ebur128->rlb_a); // apply RLB-filter bin = ebur128->z[ch * 3] * ebur128->z[ch * 3];