[FFmpeg-user] Trying to use 'ebur128' results to set up 'loudnorm'

[Mark Filipak]

Attachments:
1. original ebur128.jpg
2. loudnorm-thresh=-85 pan ebur128.jpg
3. what I want ebur128.jpg

___1. The original
has a 'shelf' just below LU = -13. That's soft speech.
The peak is at LU = +9. That's shouting.
So the transform I want goes like this:
LU = -18..-14 gets no boost.
LU = -14..+9 gets a linear boost to -11..+9.
I assume 'LU' is Loudness Unit', eh? What is a loudness unit?

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

If LU = -18..9 maps linearly to 'measured_thresh' = -99..0, then Lu = -14 is 'measured_thresh' = 
-85. I use "-85" in the next step.


___2. This command:

ffmpeg -i "original.mp4" -map 0:a -filter_complex "[0:a]loudnorm=measured_thresh=-85, 
pan=stereo|FL<FL+0.5*FC+0.6*BL+0.6*SL|FR<FR+0.5*FC+0.6*BR+0.6*SR,ebur128=video=1:peak=true[a]" -map 
"[a]" -c:v libx265 -x265-params crf=16 -c:a ac3 "loudnorm-thresh=-85 pan ebur128.mp4"

maps LU = -13..+9 to -11..-7. That brings the soft speech up wonderfully, but the shouting is dead.


___3. What I want maps LU = -14..+9 to -11..+9.
But to map linearly with 'loudnorm' I need to specify 4 parameters:
measured_I = -99..0
measured_LRA = 0..99
measured_TP = -99..99
measured_thresh = -99..0
I sorta know what 'thresh' is and I think it is '-85'. But I have no idea what 'I' and 'LRA' and 
'TP' are. I have no idea how to measure them. I have no idea what the measurement units are. And I 
have no idea what their physical meanings are.

Is there a way to measure the source video to determine these numbers? I'm partway there, but the 
rest of the way seems impossibly difficult; there's just too many unknowns.

Help! Please! I thank you,


--Mark.
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