[FFmpeg-devel] [PATCH] libavfilter: Fix incorrect ebur128 peak calculation.

[FFmpeg-devel] [PATCH] libavfilter: Fix incorrect ebur128 peak calculation.

[Carl Hetherington via ffmpeg-devel]

Since 3b26b782eeded9b9ab7fac013cd1a83a30d68206 it would only look at the
first channel.

Signed-off-by: cth@carlh.net
---
 libavfilter/f_ebur128.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavfilter/f_ebur128.c b/libavfilter/f_ebur128.c
index a352f3831f..84d8e44035 100644
--- a/libavfilter/f_ebur128.c
+++ b/libavfilter/f_ebur128.c
@@ -657,7 +657,7 @@ double ff_ebur128_find_peak_c(double *restrict ch_peaks, const int nb_channels,
     for (int ch = 0; ch < nb_channels; ch++) {
         double ch_peak = ch_peaks[ch];
         for (int i = 0; i < nb_samples; i++) {
-            const double sample = fabs(samples[i * nb_channels]);
+            const double sample = fabs(samples[i * nb_channels + ch]);
             ch_peak = FFMAX(ch_peak, sample);
         }
         maxpeak = FFMAX(maxpeak, ch_peak);
-- 
2.51.0

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[FFmpeg-devel] Re: [PATCH] libavfilter: Fix incorrect ebur128 peak calculation.

[Nicolas George via ffmpeg-devel]

Carl Hetherington via ffmpeg-devel (HE12025-11-03):
> Since 3b26b782eeded9b9ab7fac013cd1a83a30d68206 it would only look at the
> first channel.
> 
> Signed-off-by: cth@carlh.net
> ---
>  libavfilter/f_ebur128.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Hi. Thanks for the patch. I suspect the issue has been here for a longer
time, if only on one branch of the conditional build:

#if CONFIG_SWRESAMPLE
…
                const double sample = fabs(swr_samples[i * nb_channels]);
#endif

versus

            const double *restrict samples_ch = &samples[ch];
…
                const double sample = fabs(samples_ch[nb_channels * i]);

Anyway, the fix looks good to me.

Niklas, it has become mostly your code, what do you make of it?

Regards,

-- 
  Nicolas George
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[FFmpeg-devel] Re: [PATCH] libavfilter: Fix incorrect ebur128 peak calculation.

[Carl Hetherington via ffmpeg-devel]

On Tue, 4 Nov 2025, Nicolas George via ffmpeg-devel wrote:

> Carl Hetherington via ffmpeg-devel (HE12025-11-03):
> > Since 3b26b782eeded9b9ab7fac013cd1a83a30d68206 it would only look at the
> > first channel.
> >
> > Signed-off-by: cth@carlh.net
> > ---
> >  libavfilter/f_ebur128.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
>
> Hi. Thanks for the patch. I suspect the issue has been here for a longer
> time, if only on one branch of the conditional build:

[snip]

Ah, thanks for doing better git archaeology than me!

Best,
Carl
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[FFmpeg-devel] Re: [PATCH] libavfilter: Fix incorrect ebur128 peak calculation.

[Michael Niedermayer via ffmpeg-devel]

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Hi

adding niklas to the CC so its not missed
but i agree the patch LGTM

On Tue, Nov 04, 2025 at 08:52:36PM +0100, Nicolas George via ffmpeg-devel wrote:
> Carl Hetherington via ffmpeg-devel (HE12025-11-03):
> > Since 3b26b782eeded9b9ab7fac013cd1a83a30d68206 it would only look at the
> > first channel.
> > 
> > Signed-off-by: cth@carlh.net
> > ---
> >  libavfilter/f_ebur128.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Hi. Thanks for the patch. I suspect the issue has been here for a longer
> time, if only on one branch of the conditional build:
> 
> #if CONFIG_SWRESAMPLE
> …
>                 const double sample = fabs(swr_samples[i * nb_channels]);
> #endif
> 
> versus
> 
>             const double *restrict samples_ch = &samples[ch];
> …
>                 const double sample = fabs(samples_ch[nb_channels * i]);
> 
> Anyway, the fix looks good to me.
> 
> Niklas, it has become mostly your code, what do you make of it?

[...]

--
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In fact, the RIAA has been known to suggest that students drop out
of college or go to community college in order to be able to afford
settlements. -- The RIAA

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