[FFmpeg-user] Using 'ebur128' results to set 'loudnorm=measured_thresh'

Mark Filipak markfilipak.imdb at gmail.com
Tue May 21 07:12:45 EEST 2024

I've attached ebur128.jpg. It's only 37 k-bytes.

Do you see that first 'shelf' just below LU = -13? I want to boost that the most by percent, maybe 
double the power (3 dB). I want to boost LU = 9 not at all, and I want to boost everything below LU 
= -14 not at all.

So the transform I want would be like this:
LU = -18..-14 gets no boost.
LU = -14..9 gets linear boost to -7..9.
I assume 'LU' is Loudness Unit', eh? Heaven knows what the scale is and whether the scale is linear 
-- I'm used to dB, not LU. Of course, LU can't be dB because LU goes above zero.

Now, the range of 'loudnorm=measured_thresh' is -99..0, so 100 steps. Heaven knows what the scale is 
and whether the scale is linear. No matter: Pressing on...

If LU = -18..9 maps linearly to 'measured_thresh' = -99..0, then Lu = -14 is 'measured_thresh' = -85.

I'll try that and come back to this thread to report the results. Wish me luck.

Disclosure: The audio and the video in ebur128.mp4 (upon which ebur128.jpg is based) are not 
perfectly synchronized and the more I listen to the audio while looking at the slope of the graph 
roll out, the less confident I become because the graph is not going up and down with the audio. The 
truth is, I don't know what the hell 'ebur128' is telling me!

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