[FFmpeg-cvslog] avfilter/af_loudnorm: fix incorrect gain when audio is shorter than 3s

[Rui Zhu]

ffmpeg | branch: master | Rui Zhu <real.zhurui at gmail.com> | Wed Aug 31 20:51:06 2022 +0800| [36572a0c1d12459cb0fddf6ff8023b79ffa2e100] | committer: Paul B Mahol

avfilter/af_loudnorm: fix incorrect gain when audio is shorter than 3s

The input data is multiplied by `s->offset` to get normalized output.
`s->target_tp` and `true_peak` is not in dB,
so `s->offset` should be calculated by division instead of subtraction.

Signed-off-by: Rui Zhu <real.zhurui at gmail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=36572a0c1d12459cb0fddf6ff8023b79ffa2e100
---

 libavfilter/af_loudnorm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavfilter/af_loudnorm.c b/libavfilter/af_loudnorm.c
index 8d2379f14e..ce61e985b1 100644
--- a/libavfilter/af_loudnorm.c
+++ b/libavfilter/af_loudnorm.c
@@ -455,7 +455,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
 
         offset    = pow(10., (s->target_i - global) / 20.);
         offset_tp = true_peak * offset;
-        s->offset = offset_tp < s->target_tp ? offset : s->target_tp - true_peak;
+        s->offset = offset_tp < s->target_tp ? offset : s->target_tp / true_peak;
         s->frame_type = LINEAR_MODE;
     }